DIY Heatbank - fine tuning of system (incl CH)
Mike Holmes
following as a very useful starting point.
http://www.wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank
I have a couple of things of which I am currently uncertain in the
fine tuning of my setup:
1) Currently I just have a single cylinder stat which is about 400mm
or so from the bottom of the tank. I have read elsewhere regarding
the use of 2 cylinder stats and a latching relay. I understand this
is to allow the tank to work within a temperature range before the
boiler re-fires to prevent cycling. I think I get far more cycling
from my CH than from the Heatbank though - which leads on to an
additional question below. But first: what height does the 2nd stat
go on the tank? How are the 2 stats wired together? Can you buy an
off the peg latching relay to do this? If not what components are
required? Is it worth doing?
2) The CH does not go via the heatbank; this is currently just for
DHW. I have a programmable Horstmann roomstat for the CH, but am very
dissapointed at how much cycling this causes. It switches in and out
very regularly. Can anyone recommend a better unit? I have seen the
Honeywell CM67 highly spoken of, but am not sure whether it is still
made; screwfix don't list it.
3) I am aware that CH can also be fed off a heatbank, but am not sure
exactly what additional plumbing I'd need to do - would I need new
tappings into the tank, or could I just tee of the existing output
from the top of the tank and use a flow valve after the CH arm of the
tee? Currently the flow from the boiler goes system pump > 3port
valve -> 1 leg to CH flow // 1 leg to top essex flange/diffuser on the
cyclinder .
4) One curious thing I have noticed whilst becoming more intimate with
my system is that when the system pump is running a trickle of water
is coming over into the FHE tank. The problem originally started when
I moved the boiler and pump from the cellar - the flue location did
not meet current building regs when the boiler was replaced, so no
option but to relocate to 1st floor. Now the pump is obviously much
closer to the FHE tank. There is no actual overflow, but hot water is
flowing round and back down the fill pipe, which isn't ideal as the
tank is acting as a small inefficient plastic radiator in the attic,
and causing condensation to boot!! The only way I can prevent it is
to close the valve on the fill pipe, once I'm sure the system is
devoid of air. This stops the flow around through the tank,
effectively making the enclosed, but not unvented as any expansion can
still occur up the overflow pipe towards the FHE tank. I don't think
running the pump on it's lowest setting is viable - it is a 4 storey
house. The boiler and pump (and the heatbank) are all on the 1st
floor and heat has to go down 2 storeys and up 1 storey and return
obviously, so the pump needs a bit of grunt. What on earth can I do
to prevent this occuring?
5) And finally what are the optimum flow and return temps of a
condensing boiler - I have a Worcester Bosch Greenstar 24Ri (24kW). I
have seen 70/50deg C, but the heatbank needs 75-80degC, so I'd need to
go a bit higher than this. If I set the boiler too high, it tends to
cut in and out too, even if the system pump is set high, so it's a
delicate balance I need to find.
=====
For background and if anyone is interested, the following specific
info may be a useful addition to what is on the DIY Heatbanks wiki:
- The first significant improvement I to the blueprint on the wiki was
using a 100kW PHE from GEA which was about £180 incl VAT.
- The second improvement is diffuser pipes within the cylinder. I
have a c200litre direct tank [1700x500(dia) mm] double insulated. I
had the tank made to spec to fit the space I have available with a
single top port - a standard BSP 1" male connector. The top connector
takes the flow to the PHE primary and is tee'd off to the FHE tank
overflow. I added 2 essex flanges myself through which I passed my
own diffuser tubes prior to assembley of the flanges into the tank.
The diffusers are 22mm copper tube with a yorkshire end stop soldered
on and between 30 and 40 (can't recall exactly now!) 6mm holes
carefully drilled and cleaned of swarf as much as poss. The diffuser
runs across the full width of the tank from the flange to just short
of the the opposite internal side of the cylinder. The bottom flange
is 100mm from the bottom of the tank and is tee'd to take the PHE and
boiler returns (they actually flow in different directions - check the
wiki if that confuses). The top flange is for the boiler flow and is
just below the top of the cylinder side, below the join with the dome
cap. The holes on the diffuser are oriented to aim sideways and
upwards from the top diffuser and sideways and downwards from the
bottom to diffuser to preserve stratification in the tank.
d...@gglz.com
> 1) Currently I just have a single cylinder stat which is about 400mm
> or so from the bottom of the tank. I have read elsewhere regarding
> the use of 2 cylinder stats and a latching relay. I understand this
> is to allow the tank to work within a temperature range before the
> boiler re-fires to prevent cycling. I think I get far more cycling
> from my CH than from the Heatbank though - which leads on to an
> additional question below. But first: what height does the 2nd stat
> go on the tank? How are the 2 stats wired together? Can you buy an
> off the peg latching relay to do this? If not what components are
> required? Is it worth doing?
To quote from Heatweb:
"With large or fixed output boilers it may not be desirable for the
boiler to fire up when only a very small amount of store water needs
heating, as the boiler may cycle. To overcome this we can fit a second
cylinder thermostat, which will hold off the boiler from firing up
until both thermostats are calling for heat. The boiler will then fire
until both are satisfied."
Mike Holmes
Yes, I knew that!!! Read the question D'OH
fred
s.com>, Mike Holmes <mjh-n...@tiscali.co.uk> writes
LOL, I don't know if it is a good idea (the concept sounds ok) but if
you want to try it, here's how to do it:
No need for a latching relay, use a common double pole mains relay and
use the second contact to provide the latch electrically.
(Use a fixed width font)
___L
| RLY
| CONTACT A
| __- __-o
|----o' o------------------o' o---|
| LOW LVL STAT |
| __- |-----------------|
|----o' o---------|
HIGH LVL STAT |
_|_ ___L RLY
| | | CONTACT B
| | | __-o
| | |--o' o----------->
RLY |___| BOILER
COIL | CALL FOR HEAT
|
_|_ N
All contacts are shown in the no demand position, stat contacts open,
relay de-energised.
Control sequence:
1. Low level stat will close first but cannot energise the relay because
there is no direct connection to the coil.
2. High level stat closes, energising the relay and closing contacts A
and B. Contact B feeds demand to the boiler.
3. After some time heating the heat bank, the high level stat will drop
out but the relay will remain energised as it is now fed from the low
level stat via relay contact A.
4. When the low level stat drops out the relay de-energises and demand
is removed from the boiler.
Almost any 2 pole mains power relay will do the job, first one to hand
is from http://cpc.farnell.com/ , item code SW02489, 5.12 inc vat and a
screw terminal holder is code SW02484, 3.50 inc vat. Grab a plastic box
to mount it in while you're there.
It may be possible to use a single pole relay to do this job but it is
cleaner to separate the functions and 2 pole mains relays are cheap.
HTH
--
fred
Plusnet - I hope you like vanilla
John Rumm
> 1) Currently I just have a single cylinder stat which is about 400mm
> or so from the bottom of the tank. I have read elsewhere regarding
> the use of 2 cylinder stats and a latching relay. I understand this
> is to allow the tank to work within a temperature range before the
> boiler re-fires to prevent cycling. I think I get far more cycling
> from my CH than from the Heatbank though - which leads on to an
> additional question below. But first: what height does the 2nd stat
> go on the tank? How are the 2 stats wired together? Can you buy an
> off the peg latching relay to do this? If not what components are
> required? Is it worth doing?
Doing it will increase the hysteresis of the stat a bit, and delay the
recovery of the heat bank. Depending on how close you get to depleting
the heat bank this may or may not be desirable.
> 2) The CH does not go via the heatbank; this is currently just for
> DHW. I have a programmable Horstmann roomstat for the CH, but am very
> dissapointed at how much cycling this causes. It switches in and out
> very regularly. Can anyone recommend a better unit? I have seen the
> Honeywell CM67 highly spoken of, but am not sure whether it is still
> made; screwfix don't list it.
The cycle rate of the state is more an indication of the rate of change
of temperature in its current location. Is your in a draft?
(I have a Horstmann Centaur stat 7 day programmable jobbie, and don't
find that it cycles particularly quickly).
> 3) I am aware that CH can also be fed off a heatbank, but am not sure
> exactly what additional plumbing I'd need to do - would I need new
> tappings into the tank, or could I just tee of the existing output
> from the top of the tank and use a flow valve after the CH arm of the
> tee? Currently the flow from the boiler goes system pump > 3port
> valve -> 1 leg to CH flow // 1 leg to top essex flange/diffuser on the
> cyclinder .
If you used the existing ones, your would in effect run you rads at a
fairly high temperature - a lower top tapping would drop the rad temp a
bit and might give more even room temps with less overshoot. This will
be at the expense of a slightly longer warm up time from cold.
IIUC, your boiler is non modulating, so imposing the heatbank between
rads and boiler may reduce cycling a little. (with a boiler that
modulates over a wide range this is less desirable since it just
complicates the boiler ability to load balance)
> 4) One curious thing I have noticed whilst becoming more intimate with
> my system is that when the system pump is running a trickle of water
> is coming over into the FHE tank. The problem originally started when
"over into" from where? Up the Feed and Expansion pipe, or falling out
of the vent pipe?
> 5) And finally what are the optimum flow and return temps of a
> condensing boiler - I have a Worcester Bosch Greenstar 24Ri (24kW). I
> have seen 70/50deg C, but the heatbank needs 75-80degC, so I'd need to
> go a bit higher than this. If I set the boiler too high, it tends to
> cut in and out too, even if the system pump is set high, so it's a
> delicate balance I need to find.
Lower return temps are more efficient for the boiler, but you are
restricted there by the desire to get sufficient energy into the store.
I would have thought with a direct tank, it ought to keep the return
temperature reasonably down for a fair proportion of the heating time.
Some sticky tape (as a target) and an IR thermometer is handy for tuning
here so you can see what is happening with the various pipe temperatures.
--
Cheers,
John.
/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/
Doctor Drivel
"Mike Holmes" <mjh-n...@tiscali.co.uk> wrote in message
news:6da05a78-3530-4fa0...@c4g2000hsg.googlegroups.com...
> Well I have finally implemented my
> DIY Heatbank system, using the
> following as a very useful starting point.
> http://www.wiki.diyfaq.org.uk/index.php?title=DIY_Heat_Bank
I explained a better approach, but you used this one. Ignore the ridiculous
electronics. The heat web site has the circuitry of the latching relay. The
circuit has been given anyhow on this thread.
> Can anyone recommend a better unit?
The Drayton electronic is fine.
> 3) I am aware that CH can also be
> fed off a heatbank, but am not sure
> exactly what additional plumbing I'd
> need to do - would I need new
> tappings into the tank, or could I just tee
> of the existing output from the top of the
> tank and use a flow valve after the CH arm
> of the tee? Currently the flow from the boiler
> goes system pump > 3port valve -> 1 leg to
> CH flow // 1 leg to top essex flange/diffuser
> on the cylinder .
Study the heatweb site. You can use a Surrey flange in the cylinder top and
take the CH off the immersed pipe. Best to extend the inner pipe of the
flange to the centre of the cylinder. The Ch return to the bottom on the
cylinder. The room stat controls the Ch pump. The 3-way valve can go and
the boiler "only heats the cylinder directly".
> 4) One curious thing I have noticed
> whilst becoming more intimate with
> my system is that when the system
> pump is running a trickle of water
> is coming over into the FHE tank.
Take the cold feed to the DHW port away from the boiler flow influences. One
of the reason why I recommended not to use this drawing.
> 5) And finally what are the optimum
> flow and return temps of a condensing boiler
> - I have a Worcester Bosch Greenstar 24Ri (24kW). I
> have seen 70/50deg C, but the heatbank needs
> 75-80degC, so I'd need to go a bit higher than this.
A DHW only heat bank can operate at 65C, depending on cylinder size. Plate
heat exchangers are so efficient at heat transfer.
> =====
> For background and if anyone is interested,
> the following specific info may be a useful
> addition to what is on the DIY Heatbanks wiki:
> - The first significant improvement I to
> the blueprint on the wiki was using a
> 100kW PHE from GEA which was
> about £180 incl VAT.
These can be got for £80 to £100. Get a Gledhill one for a Systemate from a
dealer. DPS sell them cheaper than that too.
> The bottom flange is 100mm from the
> bottom of the tank and is tee'd to take
> the PHE and boiler returns (they actually
> flow in different directions - check the
> wiki if that confuses).
Best to have the boiler and PHE returns in separate tapings. A 200 litre
cylinder will just about do CH and DHW.
It may be worth having circuitry that brings in the boiler immediately when
DHW is called (the flow switch activated) and CH is called. This eliminates
the lag. When DHW is being called this can be switched out.
Mike Holmes
Many thanks for the detailed relies - further comments/clarifications
below:
> The cycle rate of the state is more an indication of the rate of change
> of temperature in its current location. Is your in a draft?
Well I hadn't thought so - didn't appreciate it would be so
sensitive. It is on the side of the stairs with open ballustrades
(where the old room stat was originally), so I guess there may be a
slight draft coming down off the edge of the stairs and causing it to
cycle
> (I have a Horstmann Centaur stat 7 day programmable jobbie, and don't
> find that it cycles particularly quickly).
This is exactly the model I have, so that's reassuring that it works
well for you. Will have to relocate mine I think.
> IIUC, your boiler is non modulating,
No it's fully modulating - here is the spec:
http://www.worcester-bosch.co.uk/index.php?fuseaction=product.techdata&con_id=123702
> (with a boiler that
> modulates over a wide range this is less desirable since it just
> complicates the boiler ability to load balance)
Why is that? I'm thinking that because the boiler fully modulates
that there shoudln't be a problem with having the boiler set high for
the DHW, meaning the return temp would be higher than ideal from the
CH, if the boiler DIDN'T modulate. However as my boiler DOES modulate
does this mean that even if it's on 100% (which equals 24kW and max
flow temp of 82degC) that it will actually modulate down to achieve
the ideal return temperature?
I think perhaps the problem of my system cutting in and out is
possibly purely down to the poor placement of my room stat.
>
> > 4) One curious thing I have noticed whilst becoming more intimate with
> > my system is that when the system pump is running a trickle of water
> > is coming over into the FHE tank.
>
> "over into" from where? Up the Feed and Expansion pipe, or falling out
> of the vent pipe?
I thought the feed pipe and the expansion pipe were different things
and that the expansion is synonymous with the vent pipe. Anyway in
your terminology, it is flowing out of the vent pipe and back down the
Feed and Expansion pipe. As I said there is no net overflow or actual
filling from the mains going on - just a flow through the FHE tank
that shouldn't be happening.
>>If I set the boiler too high, it tends to
> > cut in and out too, even if the system pump is set high, so it's a
> > delicate balance I need to find.
> I would have thought with a direct tank, it ought to keep the return
> temperature reasonably down for a fair proportion of the heating time.
>
It's OK on the DHW demand as you say, but I'm thinking the CH return
will end up being too high, unless the boiler's ability to modulate
down gets round this even though the boiler output is set way up.
> Some sticky tape (as a target) and an IR thermometer is handy for tuning
> here so you can see what is happening with the various pipe temperatures.
The IR thermometer was a bit pricey, so I got a digital one with a
probe from screwfix and some thermal paste from maplin to conduct
efficiently.
Thanks again
Mike
Mike Holmes
electrics mods to operate the CH off the heatbank too.
> Take the cold feed to the DHW port away from the boiler flow influences. One
> of the reason why I recommended not to use this drawing.
This occurred well before I rigged the heatbank - as explained in the
OP.
> A DHW only heat bank can operate at 65C, depending on cylinder size. Plate
> heat exchangers are so efficient at heat transfer.
Perhaps I should try dropping the temperature and see how it performs
> These can be got for £80 to £100. Get a Gledhill one for a Systemate from a
> dealer. DPS sell them cheaper than that too.
I can't vouch for the Gledhill PHEs, but I quizzed GEA about the DPS
PHE, which you may or may not have realised they supply. Personally,
what I could find out wasn't conclusive, but I wouldn't trust the data
quoted for the PHE on the DPS website. I don't pretend to fully
understand the ins and outs of the PHE head load/output calcs, but for
the input params I gave GEA their model equivalent to the one
marketted through DPS was definitely not 100kW, but needed a bigger
beast - the one I now have. Sorry to be a bit vague, I don't have the
model no and calculation sheets with me at the moment, so I can't
check and include full details. Suffice to say that my PHE is
definitely 100kW working under the conditions I supplied GEA. I
decided I'd rather spend a bit more and get a PHE that definitely did
the job rather than having to upgrade and waste money later on.
>
> > The bottom flange is 100mm from the
> > bottom of the tank and is tee'd to take
> > the PHE and boiler returns (they actually
> > flow in different directions - check the
> > wiki if that confuses).
>
> Best to have the boiler and PHE returns in separate tapings. A 200 litre
> cylinder will just about do CH and DHW.
I don't see any advantage in this - it works fine. When there is a
demand for DHW from the PHE primary pump and boiler has demand (ie the
system pump is running) the return from the PHE just cariies on
straight down the boiler return rather than going through the tank
(give or take any differences between the respective pump flows
generated - the return tapping into the bottom of the tank will
balance the flow at the tee in this scenario, to prevent any resultant
presure diffs).
John Rumm
> Many thanks for the detailed relies - further comments/clarifications
> below:
>
>> The cycle rate of the state is more an indication of the rate of change
>> of temperature in its current location. Is your in a draft?
>
> Well I hadn't thought so - didn't appreciate it would be so
> sensitive. It is on the side of the stairs with open ballustrades
> (where the old room stat was originally), so I guess there may be a
> slight draft coming down off the edge of the stairs and causing it to
> cycle
Pretty much the same place I have mine by the sounds of it.
>> (I have a Horstmann Centaur stat 7 day programmable jobbie, and don't
>> find that it cycles particularly quickly).
>
> This is exactly the model I have, so that's reassuring that it works
> well for you. Will have to relocate mine I think.
>
>> IIUC, your boiler is non modulating,
>
> No it's fully modulating - here is the spec:
>
> http://www.worcester-bosch.co.uk/index.php?fuseaction=product.techdata&con_id=123702
ah ok, the sedbuk database has it wrong then!
>> (with a boiler that
>> modulates over a wide range this is less desirable since it just
>> complicates the boiler ability to load balance)
>
> Why is that? I'm thinking that because the boiler fully modulates
> that there shoudln't be a problem with having the boiler set high for
> the DHW, meaning the return temp would be higher than ideal from the
> CH, if the boiler DIDN'T modulate. However as my boiler DOES modulate
> does this mean that even if it's on 100% (which equals 24kW and max
> flow temp of 82degC) that it will actually modulate down to achieve
> the ideal return temperature?
OK, with a modulating boiler that changes things. Usually you set the
desired flow temperature, and the boiler will adjust the power input to
achieve its desired return temperature, so it should run closer to
maximum efficiency for longer.
If you stuck the thermal store between boiler and rads then you
introduce a big energy store and damper into your closed loop control
system. The effect of which will vary depending on the details. It may
still work fine, or you might find there is enough phase lag in the
control feedback that you get erratic temperature variations.
So unless you have a very well insulated house that usually requires
significantly less than the minimum 8kW output of the boiler, you will
usually get better results letting the boiler drive the rads directly.
Note that 8kW is relatively high, so you would expect some cycling
whatever you do once the house is up to temperature.
> I think perhaps the problem of my system cutting in and out is
> possibly purely down to the poor placement of my room stat.
It could well be. How is the temperature control in the rest of the
house? Depending on the answer, you might want to play with the balance
of the uncontrolled rad in the same room as the stat.
I noticed when upgrading from a fixed output boiler with a conventional
stat, to a modulating one with prog stat the general level of comfort
and consistency in the house improved. The boiler runs for longer
periods at low output and there is less temperature swing in the house.
>>> 4) One curious thing I have noticed whilst becoming more intimate with
>>> my system is that when the system pump is running a trickle of water
>>> is coming over into the FHE tank.
>> "over into" from where? Up the Feed and Expansion pipe, or falling out
>> of the vent pipe?
>
> I thought the feed pipe and the expansion pipe were different things
> and that the expansion is synonymous with the vent pipe. Anyway in
No, you have a Feed and Expansion pipe - this will be fed from under the
water line in the header tank. It will allow water to feed into the
system, as well as allowing expansion to push water back into the tank
as the system heats up.
In addition to that you have a vent pipe that dispenses back into the
top of the tank, and it serves as a safety feature to prevent dangerous
pressure build up. Normally nothing should flow from this pipe.
It is also possible to have both these pipes combined. In this case the
vent runs as it currently does, and the F&E pipe tees into it a couple
of feet above the highest part of the system pipework.
> your terminology, it is flowing out of the vent pipe and back down the
> Feed and Expansion pipe. As I said there is no net overflow or actual
> filling from the mains going on - just a flow through the FHE tank
> that shouldn't be happening.
That is pump over, and you are right, it is not good. Not only will the
tank contents get very hot, you will also be introducing fresh air into
the water which will accelerate corrosion in the system
>>> If I set the boiler too high, it tends to
>>> cut in and out too, even if the system pump is set high, so it's a
>>> delicate balance I need to find.
>
>> I would have thought with a direct tank, it ought to keep the return
>> temperature reasonably down for a fair proportion of the heating time.
>>
>
> It's OK on the DHW demand as you say, but I'm thinking the CH return
> will end up being too high, unless the boiler's ability to modulate
> down gets round this even though the boiler output is set way up.
The modulation ought to help, but once the house is warm and the TRVs on
the rads start to close, the return temp will start to rise. There will
come a point where the boiler will have to cycle off on its own internal
stat since it won't be able to maintain the output temperature below
your selected maximum while still heating at 8kW. Usually in this case
the boiler will keep running its pump and then just kick in when the
return shows a drop again (assuming the prog stat is still calling for
heat).
Note that this type of cycling does not have the same inefficiency
drawbacks as you would get with an old high water content boiler with
external controls and pump. There each time the boiler cycled off the
retained heat would end up being lost from the flue. On yours it should
keep most of the heat in the primary circuit, and not much is lost from
the boiler anyway.
>> Some sticky tape (as a target) and an IR thermometer is handy for tuning
>> here so you can see what is happening with the various pipe temperatures.
>
> The IR thermometer was a bit pricey, so I got a digital one with a
> probe from screwfix and some thermal paste from maplin to conduct
> efficiently.
Yup, that should do it...
Dave Liquorice
>> It switches in and out very regularly.
>
> The cycle rate of the state is more an indication of the rate of change
> of temperature in its current location.
Or possibly, with a programmable stat, proportional control feature. This
is feature where the stat tries to balance the heat loss with heat input
from the boiler by pulse width modulating the firing of the boiler. The
effect is of "very regular" firing. Not recommended on systems with
motorised valves as they have to cycle far more frequently than a
traditional bang/bang system.
--
Cheers new...@howhill.com
Dave. pam is missing e-mail
Mike Holmes
Many thanks for the guidance on the latching relay circuitry - looks
pretty straightforward now I've had a chance to study it a bit.
Can anyone recommend approximate placements of the low and high stats
on the tank itself
Cheers
Mike
robgraham
> John,
>
> Many thanks for the detailed relies - further comments/clarifications
> below:
>
> > The cycle rate of the state is more an indication of the rate of change
> > of temperature in its current location. Is your in a draft?
>
> Well I hadn't thought so - didn't appreciate it would be so
> sensitive. It is on the side of the stairs with open ballustrades
> (where the old room stat was originally), so I guess there may be a
> slight draft coming down off the edge of the stairs and causing it to
> cycle
>
> > (I have a Horstmann Centaur stat 7 day programmable jobbie, and don't
> > find that it cycles particularly quickly).
>
> This is exactly the model I have, so that's reassuring that it works
> well for you. Will have to relocate mine I think.
>
> > IIUC, your boiler is non modulating,
>
> No it's fully modulating - here is the spec:
>
You didn't try Ebay then for your IR Thermometer ? A tenner (from
HK !!) and seems excellent.
Rob
i...@5roses.co.uk
> have a c200litre direct tank [1700x500(dia) mm] double insulated. I
> had the tank made to spec to fit the space I have available with a
> single top port - a standard BSP 1" male connector. The top connector
> takes the flow to the PHE primary and is tee'd off to the FHE tank
> overflow. I added 2 essex flanges myself through which I passed my
> own diffuser tubes prior to assembley of the flanges into the tank.
Hi, very interested in this thread. As wanted to build my own heatbank
too.
Latest diagram I came up with was:
http://aycu27.webshots.com/image/38786/2000028197462625313_rs.jpg
..but it still comes in expensive!!
If you have plenty of time on your hands, you can read my thread at
http://www.screwfix.com/talk/thread.jspa?threadID=63364
Couple of questions,
1.Where did you get your cylinder from and approx what price?
2. Where the essex flanges straight forward enough to fit?
3. What cylinder stats did you use and where these external or pocket
type?
4.Have you or do you intend to run Ch from heatbank or leave as is?
Cheers
Ian
Doctor Drivel
<i...@5roses.co.uk> wrote in message
news:c98b7cb0-27c7-4221...@w47g2000hsa.googlegroups.com...
- The second improvement is diffuser pipes within the cylinder. I
> have a c200litre direct tank [1700x500(dia) mm] double insulated. I
> had the tank made to spec to fit the space I have available with a
> single top port - a standard BSP 1" male connector. The top connector
> takes the flow to the PHE primary and is tee'd off to the FHE tank
> overflow. I added 2 essex flanges myself through which I passed my
> own diffuser tubes prior to assembley of the flanges into the tank.
Hi, very interested in this thread. As wanted to build my own heatbank
too.
Latest diagram I came up with was:
http://aycu27.webshots.com/image/38786/2000028197462625313_rs.jpg
<<<<<
Nice!!!
Have the open vent to the F&E tank separate to the flow to the Plate heat
exchnmager or use a Surrey flange at this point.
i...@5roses.co.uk
That is supposed to be a surrey flange on top, forgot to indicate.
Think you were part of the original screwfix thread and provided a
great deal of input so credit mainly to you!!
Just need to source a cheap 200L direct cylinder and find out if it is
straight forward enough to fit essex flanges. (I generally fit basic
kitchens and bathroom suites for housing associations so basic
plumbing OK. Used Surrey flanges before but never Essex which
obviously means cutting a hole in new cylinder!
Doctor Drivel
> have a c200litre direct tank [1700x500(dia) mm] double insulated. I
> had the tank made to spec to fit the space I have available with a
> single top port - a standard BSP 1" male connector. The top connector
> takes the flow to the PHE primary and is tee'd off to the FHE tank
> overflow. I added 2 essex flanges myself through which I passed my
> own diffuser tubes prior to assembley of the flanges into the tank.
Hi, very interested in this thread. As wanted to build my own heatbank
too.
Latest diagram I came up with was:
http://aycu27.webshots.com/image/38786/2000028197462625313_rs.jpg
<<<
Put the check valves on the CH circuits "after" the pumps.
Bob Mannix
news:477ada5e$0$47136$892e...@authen.yellow.readfreenews.net...
Also interested as it seems an excellent post-fix to a system with a newish
boiler.
Advantages over (say) a combi would seem to be flow rate but the biggest
combi advantage is infinite capacity (at whatever flow rate one can argue
they deliver).
Web sites for thermal stores don't seem to quote capacity of drawn off hot
water. Let's say (hypothetically) one has a thermal store with a tank of
water of 300l at 80degC and a plate heat exchanger set to deliver DHW at
65degC. At a flow rate of (say) 30l/min, how long does the hot water last
(at that flow rate, boiler heating will be too slow to be significant). Or,
in non scientific units, how many full baths can you run one after the
other? I should be able to work it out,from the physics I guess, but someone
should know!!
--
Bob Mannix
(anti-spam is as easy as 1-2-3 - not)
Doctor Drivel
"Bob Mannix" <b1o...@mannix.org.uk> wrote in message
news:flftfc$h0f$1...@south.jnrs.ja.net...
> "Doctor Drivel" <Min...@nospam.com> wrote in message
> news:477ada5e$0$47136$892e...@authen.yellow.readfreenews.net...
>>
>> <i...@5roses.co.uk> wrote in message
>> news:c98b7cb0-27c7-4221...@w47g2000hsa.googlegroups.com...
>> - The second improvement is diffuser pipes within the cylinder. I
>>> have a c200litre direct tank [1700x500(dia) mm] double insulated. I
>>> had the tank made to spec to fit the space I have available with a
>>> single top port - a standard BSP 1" male connector. The top connector
>>> takes the flow to the PHE primary and is tee'd off to the FHE tank
>>> overflow. I added 2 essex flanges myself through which I passed my
>>> own diffuser tubes prior to assembley of the flanges into the tank.
>>
>>
>> Hi, very interested in this thread. As wanted to build my own heatbank
>> too.
>>
>> Latest diagram I came up with was:
>>
http://aycu27.webshots.com/image/38786/2000028197462625313_rs.jpg
>> <<<
>>
>
> Also interested as it seems an excellent post-fix to a system with a
> newish boiler.
>
> Advantages over (say) a combi would seem to be flow rate but the biggest
> combi advantage is infinite capacity (at whatever flow rate one can argue
> they deliver).
This heat bank system has many advantages.
Look at the flow pipe from the boiler into the cylidner. Take this pipe
inside the cylinder and bend it up towarads the DHW draw-off at the top,
terminating inside the dome pointing up. The flow would be sucked into the
plate heat X by the DHW pump. When the store is exhausted of heat the flow
rate will revert to what the boiler can give, which will be a good shower at
least and "never" run out of hot water. This principle is applied to stored
water combis which are two stage: high flow using stored water and low rate
using only the ouput of the boilers burner.
You could use the flow switch to always bring in the boiler always when DHW
is called. This "combines" the output of the boiler and the heat of the
stored water, giving greater capacity - or the cyldiner culd be dopwnsized
using this method. A high limit stat would need to be on the cylinder to cut
out the boiler if the temperature was above 95C.
The diagram uses two CH zones off the store using Wilo Smart pumps. This is
a great advantage, as only 0.5 kW will be drawn-off if need be. All rads
can then have TRVs on them. This increases comfort conditions.
The boiler only heats the store so running without cycling and to maximum
effciency and flow throught it at all times. One of the big problems with
boilers fitted these days, is that the auto-by-pass is incorrectly set,
allowing too much flow through a condensing boiler reducing its efficiency
or in many cases too little flow and reducing the lifespan of the heat
exchanger. A boiler heating a store has no such problems and will outlast
boilers coupled directly to rads with TRVs on the rads. Also a simple,
cheaper, more reliable non-modulating boiler can be fitted.
> Web sites for thermal stores don't seem to quote capacity of drawn off hot
> water. Let's say (hypothetically) one has a thermal store with a tank of
> water of 300l at 80degC and a plate heat exchanger set to deliver DHW at
> 65degC. At a flow rate of (say) 30l/min, how long does the hot water last
> (at that flow rate, boiler heating will be too slow to be significant).
> Or, in non scientific units, how many full baths can you run one after the
> other? I should be able to work it out,from the physics I guess, but
> someone should know!!
Later...
John Rumm
>> Latest diagram I came up with was:
>> http://aycu27.webshots.com/image/38786/2000028197462625313_rs.jpg
>> <<<
>>
>
> Also interested as it seems an excellent post-fix to a system with a newish
> boiler.
Depending on the sophistication of the boiler and control systems you
may get better results with the rads driven directly rather than from
the store.
> Advantages over (say) a combi would seem to be flow rate but the biggest
> combi advantage is infinite capacity (at whatever flow rate one can argue
> they deliver).
That is not really any different with a store - at some point once you
have used any stored heat, the rate at which you can draw further heat
from it will be governed by how fast the boiler can replenish it.
However this will equate to a significant drop in delivery rate since
you can draw energy from the store at a rate well above that which you
can get from your gas supply.
> Web sites for thermal stores don't seem to quote capacity of drawn off hot
> water. Let's say (hypothetically) one has a thermal store with a tank of
> water of 300l at 80degC and a plate heat exchanger set to deliver DHW at
> 65degC. At a flow rate of (say) 30l/min, how long does the hot water last
Say you are drawing 30lpm of water at 60 deg that is being heated from
(say) 5 deg, you require a heating power of (60 - 5) x 4200 x 30 / 60 =
115.5 kW
> (at that flow rate, boiler heating will be too slow to be significant). Or,
Not necessarily... if the boiler is kicked in by a flow switch at the
start of the draw off, a 20kW boiler would be replacing a 5th of the
energy used in real time. So you reduce the effective energy transfer
rate from the store to 95.5 kW
> in non scientific units, how many full baths can you run one after the
> other? I should be able to work it out,from the physics I guess, but someone
> should know!!
Lets say you want 200L of 45 deg water for the bath, that means you want
145 l of hot water. It will take 4.8 mins to fill the bath. You have had
33.5MJ out of the store, so at say 20kW (1.2 MJ/min) input it will take
about half an hour to replenish fully. So you can have baths every half
hour indefinitely, or faster for a limited time. Obviously smaller
baths and more powerful boilers can change that picture dramatically.
Bob Mannix
news:13nn7dn...@corp.supernews.com...
Thanks for the calcs- surely it may be slightly better than that though. The
requirement for 145l of hot water might be met twice over by a store
(depending on its size) so one might get 2 baths then wait an hour, which
is, of course the same on average, but practically may be a lot better! It
was the gearing between the size of the store and DHW run-off I was looking
for. Looking at the websites on the PHE, for 80degC store, it would seem
that 150l flow of hot water out of the PHE would need about 100l of water
from the store flowing into it - a 210l or above store would then give two
baths (roughly) before the system is cold (ie not able to perform at full
spec). Does this sound right?
John Rumm
>>> in non scientific units, how many full baths can you run one after the
>>> other? I should be able to work it out,from the physics I guess, but
>>> someone should know!!
>> Lets say you want 200L of 45 deg water for the bath, that means you want
>> 145 l of hot water. It will take 4.8 mins to fill the bath. You have had
>> 33.5MJ out of the store, so at say 20kW (1.2 MJ/min) input it will take
>> about half an hour to replenish fully. So you can have baths every half
>> hour indefinitely, or faster for a limited time. Obviously smaller baths
>> and more powerful boilers can change that picture dramatically.
>
> Thanks for the calcs- surely it may be slightly better than that though. The
> requirement for 145l of hot water might be met twice over by a store
> (depending on its size) so one might get 2 baths then wait an hour, which
> is, of course the same on average, but practically may be a lot better! It
Yup, that is what I meant by "every half hour indefinitely, or faster
for a limited time" ;-)
Although looking again at the figures - you probably can't draw that
much energy out of the store without it impacting the final water temp a
little toward the end...
that 33.5MJ would represent a 26.5 degree store temperature drop without
any replenishment. With 20kW going back in that would be a 22 degree
drop. So the last bit of the bath fill would start to cool very
slightly. If you were sticking 35kW back in then you would only see a 16
degree drop in the store and output temp would be unaffected.
> was the gearing between the size of the store and DHW run-off I was looking
> for. Looking at the websites on the PHE, for 80degC store, it would seem
Well if you allow a couple of degrees from loss on the PHE, then that
18 degree difference represents (so 300 * 4200 * 18 = 22.7MJ) of energy.
Once you have drawn that and without any replenishment then the output
temp from the PHE will start to fall below 60. That equates to about
100l of drawn water.
> that 150l flow of hot water out of the PHE would need about 100l of water
> from the store flowing into it - a 210l or above store would then give two
> baths (roughly) before the system is cold (ie not able to perform at full
> spec). Does this sound right?
Not quite - you can't usefully get all of the energy out of the store
unless you can accept a lower final water temperature. If you say that
the minimum useful temperature of the store water is 50 degrees (to
allow draw off at say 48 deg), and the maximum store temp is 80, then
you have 30 x 4200 x 300 = 37.8 MJ for water heating with a 300l store.
With ground water at 5 degs (i.e. worst case in the winter) and a bath
at 45 final temperature, that gives you no more than 300 / 40 x 30 = 225
l of hot water without replenishment. So with the boiler running, you
can probably just squeeze two deep baths in quick succession out of the
store. You would also need to adjust taps from time to time to allow for
the falling hot water temperature.
i...@5roses.co.uk
rather than further down, (and perhaps boiler is better connected
using a surrey flange at top of cylinder), the output of the boiler is
mainly going straight to the PHE. Therefore, although flow rate may
have to be adjusted, you could continue to fill baths infinitely. This
would act like a combi so would just take a bit longer to fill.
On the point of........
"Depending on the sophistication of the boiler and control systems
you
may get better results with the rads driven directly rather than from
the store"
This is something I'm struggling with as boiler is new condensing.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
news:13nn7dn...@corp.supernews.com...
>
>>> Latest diagram I came up with was:
>>> http://aycu27.webshots.com/image/38786/2000028197462625313_rs.jpg
>>> <<<
>>>
>>
>> Also interested as it seems an excellent post-fix to a system with a
>> newish boiler.
>
> Depending on the sophistication of the boiler and control systems you may
> get better results with the rads driven directly rather than from the
> store.
Chav, please be quiet and do not comment on things you know sweet FA about.
Doctor Drivel
<i...@5roses.co.uk> wrote in message
news:8517ec55-bce1-4848...@s12g2000prg.googlegroups.com...
Not a problem. The bottom of the store will be quite cool and condensing
will occur most of boiler run time. Most boilers only modulate to about 7
to 8 kW minimum. Lower than that and boioer cycling occurs. Taking the CH
off the store means that only 0.5 kW can be drawn off the store and no
boiler cycling. Then no auto-by -passes that can affect the boiler,
centralised room stats that cut out the boiler when some rooms may need
heat, etc.
When a boiler is heating rads directly with all rads except one with TRVs
and an auto by-pass fitted, when all or most TRVs close up the auto by-pass
opens up and hot water flows back to the boiler, then the boioer efficiency
drops like a stone.
John Rumm
> But surely as the boiler is supplying to the top of the cylinder
> rather than further down, (and perhaps boiler is better connected
> using a surrey flange at top of cylinder), the output of the boiler is
> mainly going straight to the PHE. Therefore, although flow rate may
> have to be adjusted, you could continue to fill baths infinitely. This
> would act like a combi so would just take a bit longer to fill.
Of a sort, yes. However the drop in performance from a 115kW combi to a
(say) a 20kW one will make a dramatic difference in performance: 30 lpm
of 60 degree water down to 9 lpm of 40 degree water. So you could fill
that last bath slowly, but someone expecting shower at the same time is
in for a bit of a shock.
> On the point of........
> "Depending on the sophistication of the boiler and control systems
> you
> may get better results with the rads driven directly rather than from
> the store"
>
> This is something I'm struggling with as boiler is new condensing.
I note on your schematic you had a blending valve on the boilers return.
Presumably to maintain a minimum return temperature. While this is
common practice where one wants to prevent an older design of boiler
from seeing excessive periods of low return temperatures, it would be
counter productive on a condensing boiler since there is no requirement
to maintain a minimum return temperature. Artificially raising the
apparent return temperature when cooler water is available would just
lower the boilers condensing efficiency. It also adds an extra tapping
to the top of the tank and associated pipework.
If you have a high end "smart" boiler with analogue room temp sensing or
external weather compensation, then you would loose the ability to run
very low flow temperatures through the rads during the milder parts of
the year.
The presence of a big energy store between the boiler and rads can also
affect the performance of the boilers control system since it introduces
a big damping and delaying effect - possibly leading to unexpected
fluctuation of the store temp in response to changing heating loads, and
hence reduction in performance on hot water delivery. You also incur the
cost of the two extra pumps for these circuits.
You need to balance the cost and complexity of all the hardware against
what gains you get (both in performance terms and also running and
maintenance costs). You may well find a decent boiler with a simpler S
Plan+ system driving the rads directly and the store as another zone
would work equally well or better.
John Rumm
LOL!, one could suggest you do the same. You have demonstrated many
times that your lack of grasp of control theory, surpasses even your
famously poor grasp of basic physics.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> Doctor Drivel wrote:
>>
>> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>> news:13nn7dn...@corp.supernews.com...
>>> Bob Mannix wrote:
>>>
>>>>> Latest diagram I came up with was:
>>>>> http://aycu27.webshots.com/image/38786/2000028197462625313_rs.jpg
>>>>> <<<
>>>>>
>>>>
>>>> Also interested as it seems an excellent post-fix to a system with a
>>>> newish boiler.
>>>
>>> Depending on the sophistication of the boiler and control systems you
>>> may get better results with the rads driven directly rather than from
>>> the store.
>>
>> Chav, please be quiet and do not comment on things you know sweet FA
>> about.
>
> LOL!,
Chav, the man has come here for advice. There are people here who know this
field backwards and their experience does not entail fitting one combi.
Please be quiet and do not comment on things you know sweet FA about.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
This is what happened when know-it-alls think they do actually know
something.
> I note on your schematic you had a blending valve on the boilers return.
> Presumably to maintain a minimum return temperature. While this is common
> practice where one wants to prevent an older design of boiler from seeing
> excessive periods of low return temperatures,
Chav, it is to maintain a high flow temperature into the thermal store for
DHW purposes. The CH section of the cylinder need not have the return
blending valve on the flow/return. It also keeps the boiler within its delta
T ensuring correct operation and longevity of the heat exchanger..
> it would be counter productive on a condensing boiler since there is no
> requirement to maintain a minimum return temperature.
There is a requirement to maintain a Deta T on all boilers
> Artificially raising the apparent return temperature when cooler water is
> available would just lower the boilers condensing efficiency.
DHW has to be....well hot. And there is no getting away from the fact that
the return temp will rise to create DHW. The Blending valve may be set to
50C with a boiler giving a 25C temperature rise. Many stores may run at 70C
comfortably as plate Heat Xs are so efficient. That is a return temp of 45C,
which is very efficient.
> If you have a high end "smart" boiler with analogue room temp sensing or
> external weather compensation, then you would loose the ability to run
> very low flow temperatures through the rads during the milder parts of the
> year.
No boiler modulates very low and they all cycle. He can fit a weather
compensator to the CH section of the cylinder and lower and raise that water
body to maintain outside weather influence and this will result in very low
return boiler temperatures being created.
<snip a load of ill-informed crap!!!>
John Rumm
> <a load of ill-informed crap!!!>
Par for the course...
i...@5roses.co.uk
> Presumably to maintain a minimum return temperature. While this is
> common practice where one wants to prevent an older design of boiler
> from seeing excessive periods of low return temperatures, it would be
> counter productive on a condensing boiler since there is no requirement
> to maintain a minimum return temperature. Artificially raising the
> apparent return temperature when cooler water is available would just
> lower the boilers condensing efficiency. It also adds an extra tapping
> to the top of the tank and associated pipework.
Blending valve added as it was suggested on the original thread that
the temperature difference between the boiler flow and return should
be around the 20 deg mark to allow optimum condensing. To be fair,
when I asked DPS for a quote, they included a blending valve too on
their spec. In fact they said it should be a 28mm version for boilers
of >20KW as the internal parts on a 22mm were too small.
>
> If you have a high end "smart" boiler with analogue room temp sensing or
> external weather compensation, then you would loose the ability to run
> very low flow temperatures through the rads during the milder parts of
> the year.
>
> The presence of a big energy store between the boiler and rads can also
> affect the performance of the boilers control system since it introduces
> a big damping and delaying effect - possibly leading to unexpected
> fluctuation of the store temp in response to changing heating loads, and
> hence reduction in performance on hot water delivery. You also incur the
> cost of the two extra pumps for these circuits.
It was considered better to use pumps rather than zoning valves due to
reliability.
In all honesty, I just want a good mains presure system that will
supply enough hot water for 2 showers running at once, where I don't
have to wait 30min+ to refill a bath and that ideally gives me 2
zones(upstairs and downstairs). I have a new 28KW condensing system
boiler and now need a cylinder. Don't want to pay £1300+ from DPS for
same design as you see here (and that's kit form and no metal casing
round the copper cylinder to make it look pretty either !) and don't
want an unvented. Had liked the idea of CH off the store but really
only due to the fact that the contents of the store could be dumped
into the rads for instant heat.If I could get something for around
£800 I think I'd be happy!!!
John Rumm
>> I note on your schematic you had a blending valve on the boilers return.
>> Presumably to maintain a minimum return temperature. While this is
>> common practice where one wants to prevent an older design of boiler
>> from seeing excessive periods of low return temperatures, it would be
>> counter productive on a condensing boiler since there is no requirement
>> to maintain a minimum return temperature. Artificially raising the
>> apparent return temperature when cooler water is available would just
>> lower the boilers condensing efficiency. It also adds an extra tapping
>> to the top of the tank and associated pipework.
>
> Blending valve added as it was suggested on the original thread that
> the temperature difference between the boiler flow and return should
> be around the 20 deg mark to allow optimum condensing. To be fair,
> when I asked DPS for a quote, they included a blending valve too on
> their spec. In fact they said it should be a 28mm version for boilers
> of >20KW as the internal parts on a 22mm were too small.
Yup, that I what I thought it looked like they were trying to do... It
makes good sense on a fixed output boiler, and especially on a non
condenser. Not so sure it adds much with a condenser that will modulate
to lower return temperatures, and will give best condensing performance
with the lowest return temperature available....
As an aside, have you considered using a indirect store with a fast
recovery coil carrying the primary heating water? That would allow the
use of a sealed system primary to drive the rads and the store. Would do
away with the header tank as well. You could then have a quite simple
system that would also provide the hot water performance you want
without needing an unvented cylinder.
> It was considered better to use pumps rather than zoning valves due to
> reliability.
Simple two port valves seem quite reliable if exercised from time to
time during the summer...
> In all honesty, I just want a good mains presure system that will
> supply enough hot water for 2 showers running at once, where I don't
> have to wait 30min+ to refill a bath and that ideally gives me 2
> zones(upstairs and downstairs). I have a new 28KW condensing system
Yup, makes sense. Since you have the modern boiler, and I take it you
have enough cold mains flow rate available, I would be inclined to leave
the rads driven directly by the boiler (in their own zones). With a prog
stat per zone and TMVs on the rads you are going to end up with pretty
good efficiency and performance anyway on the space heating. Even if the
boiler does cycle a little when the house is warmed up, that is far less
of an issue with modern low water content boilers.
> boiler and now need a cylinder. Don't want to pay Ł1300+ from DPS for
> same design as you see here (and that's kit form and no metal casing
> round the copper cylinder to make it look pretty either !) and don't
> want an unvented. Had liked the idea of CH off the store but really
> only due to the fact that the contents of the store could be dumped
> into the rads for instant heat.If I could get something for around
> Ł800 I think I'd be happy!!!
Its easy to end up adding more and more complexity to these solutions
and before long the parts bill alone is scary (something you have to
watch with Dr. Dribble's designs - they soon end up with half the
contents of the BES catalogue used in there somewhere!)
i...@5roses.co.uk
> As an aside, have you considered using a indirect store with a fast
> recovery coil carrying the primary heating water? That would allow the
> use of a sealed system primary to drive the rads and the store.
I have considered using another PHE to heat the store(particularly as
my boiler is ideally supposed to work on sealled systems but will
apparently work on vented if pressure sensor is disconnected). Thought
this better than coil as can be cleaned easily if necessary. Also I
assume order of efficiency is coil,PHE and best is heat store direct.
>Would do
> away with the header tank as well. You could then have a quite simple
> system that would also provide the hot water performance you want
> without needing an unvented cylinder.
>
Wouldn't I still need the tank as
a) stored water will still expand
b) stored water will need topping up from time to time?
Doctor Drivel
> i...@5roses.co.uk wrote:
> Yup, that I what I thought it looked like they were trying to do... It
> makes good sense on a fixed output boiler, and especially on a non
> condenser. Not so sure it adds much with a condenser that will modulate to
> lower return temperatures,
Chav, you really haven't a clue, even after an explanation. It guarantees
the highest temperature set so only very hot water enters the store at the
top of the cylinder ready for use to give useful DHW, even after 2 minutes
of running from cold a sink can be filled. It also guarantees the boiler is
operating within its delta T and maximises thermal expansion. It guarantees
top down heating of the store and the water is heater one pass of the boiler
quickening the re-heat. It also increases boiler longevity as the boiler is
operating in an ideal hydraulic environment.
<snip ill-informed tripe>
>> It was considered better to use pumps rather than zoning valves due to
>> reliability.
>
> Simple two port valves seem quite reliable if exercised from time to time
> during the summer...
Again the ignorance abounds. Having the two pumps means the CH zones are
fully independent (one has no effect on the other which is not the case when
using one pumps and zone valves) of each other as they both go back to the
neutral point - the store - which means superior balancing of rads and that
two smart pumps may be used using TRVs on "all" rads. Also the pumps can
inject even 0.25 kW into their respective CH zones, increasing comfort.
>> In all honesty, I just want a good mains presure system that will
>> supply enough hot water for 2 showers running at once, where I don't
>> have to wait 30min+ to refill a bath and that ideally gives me 2
>> zones(upstairs and downstairs). I have a new 28KW condensing system
>
> Yup, makes sense. Since you have the modern boiler, and I take it you have
> enough cold mains flow rate available, I would be inclined to leave the
> rads driven directly by the boiler (in their own zones).
That is because you know sweet FA about thermal storage and heating systems.
> With a prog stat per zone and TMVs on the rads you are going to end up
> with pretty good efficiency and performance anyway on the space heating.
> Even if the boiler does cycle a little when the house is warmed up, that
> is far less of an issue with modern low water content boilers.
The boiler still cycles, and the auto by-pass will eventually restrict flow
through the boiler as it wears or open up too early and elinminates
condensing as a direct short cut is created.
>> boiler and now need a cylinder. Don't want to pay £1300+ from DPS for
>> same design as you see here (and that's kit form and no metal casing
>> round the copper cylinder to make it look pretty either !) and don't
>> want an unvented. Had liked the idea of CH off the store but really
>> only due to the fact that the contents of the store could be dumped
>> into the rads for instant heat.If I could get something for around
>> £800 I think I'd be happy!!!
Having the CH zones off the store is a great bonus. Having the boiler only
heat the heat bank cylinder is great bonus.
The store is a great neutral point. Each function of the system can be
isolated and optimised and one does not influence the other. The boiler is
de-coupled and optimised for performance. As are the CH zones, as is the DHW
take off too. The boiler can be optimised for condensing efficiency - heat
bank setpoint of 70C and return temperature of 45C. This means the boiler
condenses the vast majority of run time and operates in an ideal hydraulic
environment.
Forget all this tripe that a modulating boiler is the best option coupled to
rads. It may be if it modulates from 0kW to 27kW and no TRVs on the rads.
As no boiler goes down to 0kW that will not happen. The auto by-pass screws
up efficiency performance and the cycling reduces reliability putting
heavier demand on controls. The auto by-pass can screw up the heat exchanger
is not enough flow is allowed through the rad.
Most of the time a boiler is on part load, and this means a lot of the time
the auto by-pass valve is open eliminating condensing competely with
efficiency dropping like a stone.
<snip ill-informed tripe by Chav!>
Doctor Drivel
<i...@5roses.co.uk> wrote in message
news:b634a5b7-1b9c-4b29...@s19g2000prg.googlegroups.com...
> I have considered using another
> PHE to heat the store (particularly as
> my boiler is ideally supposed to work
> on sealled systems but will apparently
> work on vented if pressure sensor is
> disconnected).
I assume you mean the low pressure sensor. See this:
http://www.copperform.co.uk/mains_pressure/thermaflow/index.htm
This is a pressurised store running at 2.5 bar, so the boiler will operate
fine. Can be DIYed using plate heat Xs. They may make one to order without
the coil and insert the tapping where you want.
> Thought this better than coil as can be
> cleaned easily if necessary. Also I
> assume order of efficiency is coil,PHE
> and best is heat store direct.
I think you mean in reverse order. The coil is way less efficient than a
plate heat X. Direct is the ultimate.
Bob Mannix
> "John Rumm" <see.my.s...@nowhere.null> wrote in message
> news:13nr4l5...@corp.supernews.com...
>> i...@5roses.co.uk wrote:
>
>> Yup, that I what I thought it looked like they were trying to do... It
>> makes good sense on a fixed output boiler, and especially on a non
>> condenser. Not so sure it adds much with a condenser that will modulate
>> to lower return temperatures,
>
> Chav, you really haven't a clue, even after an explanation. It guarantees
> the highest temperature set so only very hot water enters the store at the
> top of the cylinder ready for use to give useful DHW, even after 2 minutes
> of running from cold a sink can be filled. It also guarantees the boiler
> is operating within its delta T and maximises thermal expansion. It
> guarantees top down heating of the store and the water is heater one pass
> of the boiler quickening the re-heat. It also increases boiler longevity
> as the boiler is operating in an ideal hydraulic environment.
>
["Chav" is a stupid and judgemental term and I do not wish to be asscoiated
with it.] On the other hand, DD's explanation for the blending valve seems
plain common sense and was part of my assumption. Also these thermal store
systems only work well (high hot water flow) if the primary side of the PHE
(and hence the store itself) is at a very high temperature (75-90degC). This
can only be achieved by subtracting the boiler's maximum delta-T from the
desired temperature and ensuring the answer is used as the set point for the
return water. The condensing efficiency argument is irrelevant as the whole
system won't work without the higher than normal return temperature.
John Rumm
>> As an aside, have you considered using a indirect store with a fast
>> recovery coil carrying the primary heating water? That would allow the
>> use of a sealed system primary to drive the rads and the store.
>
> I have considered using another PHE to heat the store(particularly as
> my boiler is ideally supposed to work on sealled systems but will
> apparently work on vented if pressure sensor is disconnected). Thought
> this better than coil as can be cleaned easily if necessary. Also I
> assume order of efficiency is coil,PHE and best is heat store direct.
Another PHE would do the trick quite nicely. While these are not cheap,
you would not need such a large one for this application since the
boiler power is the limiting factor here. You may even save equal or
more money by not needing an expensive cylinder with fast recovery coil.
(any direct tank could be used). Water to water PHEs are quite efficient
so you would not loose much if anything over pumping the primary through
a direct store.
>> Would do
>> away with the header tank as well. You could then have a quite simple
>> system that would also provide the hot water performance you want
>> without needing an unvented cylinder.
>>
>
> Wouldn't I still need the tank as
> a) stored water will still expand
Your system boiler will already include an expansion vessel designed to
cope with the expansion of the primary circuit. The water in the store
itself will also expand and contract, but this does not need to be
hermetically sealed and can have a small expansion gap at the top
(assuming your pumped PHE connections are via side tappings on Essex
flanges).
> b) stored water will need topping up from time to time?
It can be filled from a hose (or suitably positioned fixed pipework and
tap of some sort). The only route of water loss from it will be via
evaporation.
Doctor Drivel
>
> "Doctor Drivel" <Min...@nospam.com> wrote in message
> news:477e2a9b$0$47116$892e...@authen.yellow.readfreenews.net...
>> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>> news:13nr4l5...@corp.supernews.com...
>>> i...@5roses.co.uk wrote:
>>
>>> Yup, that I what I thought it looked like they were trying to do... It
>>> makes good sense on a fixed output boiler, and especially on a non
>>> condenser. Not so sure it adds much with a condenser that will modulate
>>> to lower return temperatures,
>>
>> Chav, you really haven't a clue, even after an explanation. It
>> guarantees the highest temperature set so only very hot water enters the
>> store at the top of the cylinder ready for use to give useful DHW, even
>> after 2 minutes of running from cold a sink can be filled. It also
>> guarantees the boiler is operating within its delta T and maximises
>> thermal expansion. It guarantees top down heating of the store and the
>> water is heater one pass of the boiler quickening the re-heat. It also
>> increases boiler longevity as the boiler is operating in an ideal
>> hydraulic environment.
>>
>
> ["Chav" is a stupid and judgemental term and I do not wish to be
> asscoiated with it.]
A Chav is a Chav and he is one. And like you I want nothing to do with
them. All those tattoos and heavy jewellery!
> On the other hand, DD's explanation for the blending valve seems plain
> common sense and was part of my assumption. Also these thermal store
> systems only work well (high hot water flow) if the primary side of the
> PHE (and hence the store itself) is at a very high temperature
> (75-90degC).
Nope. Plate heat exchangers are so efficient (and some are better than
others, like the Danfoss two-pass and the Swep used by Gledhill), that a
store temperature of 65C can be set and they will give more than adequate
DHW. The higher the temperature the more energy stored and the smaller the
cylinder, the lower the temp the larger the water store.
> The condensing efficiency argument is irrelevant as the whole system won't
> work without the higher than normal return temperature.
More old wives tales. A longish cylinder ensures that the bottom of the
cylinder has "very" low temperatures - superior stratification. Plate heat
Xs are so efficient at extracting heat the return temperature from them will
be 30C and below.
Thermal stores using an immersed coil DHW take off require higher
temperatures because the coils are so inefficient to a plate heat OX.
A well designed CH & DHW heat bank knocks cobs off a direct to the rads
boiler CH system. They are very efficient and highly reliable.
The design presented is a good one. If the points I suggested to improve
are implemented and the CH section heated direct not via a return blending
valve (a 3-way diverter valve is needed) a weather compensator controlling
in the water temperature in the CH section of the store the efficiency will
be "very" high.
Heat bank - plate heat X DHW
thermals store = immersed coil DHW
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> i...@5roses.co.uk wrote:
>>> As an aside, have you considered using a indirect store with a fast
>>> recovery coil carrying the primary heating water? That would allow the
>>> use of a sealed system primary to drive the rads and the store.
>>
>> I have considered using another PHE to heat the store(particularly as
>> my boiler is ideally supposed to work on sealled systems but will
>> apparently work on vented if pressure sensor is disconnected). Thought
>> this better than coil as can be cleaned easily if necessary. Also I
>> assume order of efficiency is coil,PHE and best is heat store direct.
>
> Another PHE would do the trick quite nicely. While these are not cheap,
> you would not need such a large one for this application since the boiler
> power is the limiting factor here. You may even save equal or more money
> by not needing an expensive cylinder with fast recovery coil. (any direct
> tank could be used). Water to water PHEs are quite efficient so you would
> not loose much if anything over pumping the primary through a direct
> store.
It is cheaper, far more efficient in economy, and far quicker using a plate
heat X and bronze pump heating up a large direct cylinder. 95% plus of the
boilers heat is extracted via the plate and put into the fresh water in the
cylinder.
Here is an off-the-shelf model:
<http://www.mcdonald-engineers.com/products/plateflow.htm>
>>> Would do
>>> away with the header tank as well. You could then have a quite simple
>>> system that would also provide the hot water performance you want
>>> without needing an unvented cylinder.
>>>
>>
>> Wouldn't I still need the tank as
>> a) stored water will still expand
>
> Your system boiler will already include an expansion vessel designed to
> cope with the expansion of the primary circuit. The water in the store
> itself will also expand and contract, but this does not need to be
> hermetically sealed and can have a small expansion gap at the top
> (assuming your pumped PHE connections are via side tappings on Essex
> flanges).
>
>> b) stored water will need topping up from time to time?
>
> It can be filled from a hose (or suitably positioned fixed pipework and
> tap of some sort). The only route of water loss from it will be via
> evaporation.
You are describing a DPS Pandora. They have a few safety controls on that
and a deflated expansion vessel on the top of the cylinder.
John Rumm
> On the other hand, DD's explanation for the blending valve seems
> plain common sense and was part of my assumption. Also these thermal store
> systems only work well (high hot water flow) if the primary side of the PHE
> (and hence the store itself) is at a very high temperature (75-90degC). This
> can only be achieved by subtracting the boiler's maximum delta-T from the
> desired temperature and ensuring the answer is used as the set point for the
> return water. The condensing efficiency argument is irrelevant as the whole
> system won't work without the higher than normal return temperature.
The blending valve will indeed keep the boiler flow hotter (at least in
the early recovery stages after heavy demands have been made on the
store, and assuming you have very well controlled stratification in the
store), but there are many interacting variables and trade-offs here.
These are at their most complex with a directly heated store since you
can't control the heating load presented to the boiler as easily. It is
worth bearing in mind that this design is being proposed for use with a
modern modulating, condensing boiler that supports wide temperature
deltas. The whole "thermal store with everything hung off it" design
concept is very well suited to older boiler designs where long burns,
reduced cycling, high flow temps (and maintained above a threshold
return temps) are all "good things". Hence you have a nice "rule of
thumb" solution to a number of problems. The whole situation is much
less clear cut here.
Dribble is right that running rads from the store will let them run at
low powers, which was a big gain when the alternative was 20kW or
nothing and a mechanical stat overseeing the outer loop control. When
the choice is anything from 7[1] to 28kW or nothing and tighter outer
loop control, you are not going to notice much difference in a typical
house with a few kW of heat losses.
([1] number picked at random - I don't know how low the OPs boiler will
modulate).
Higher store temps are obviously good from an overall energy density
point of view, but less good from a condensing efficiency one. The
temperature you set for your hot water take off also has a big impact
since it dictates how much headroom you have under the store
temperature, and when falling store temperature will start to impact on
the HW temperature. Opting for water at a temperature close to that of
final use, and with less mixing at the point of use, will give more
consistent water temperature output form the store with less worries
about maintaining high and well stratified store temperatures.
With the modern boiler, the most efficient way to get the high flow temp
is to take advantage of a bigger delta T. If your boiler supports
analogue control, then even better. You can select higher temps for
replenishing the store, and much lower ones for running the heating
(which is where you will probably spend most of your money - and so
efficiency is of greatest importance).
Doctor Drivel
>
> "John Rumm" <see.my.s...@nowhere.null> wrote in message
> news:13nsise...@corp.supernews.com...
>> i...@5roses.co.uk wrote:
>>>> As an aside, have you considered using a indirect store with a fast
>>>> recovery coil carrying the primary heating water? That would allow the
>>>> use of a sealed system primary to drive the rads and the store.
>>>
>>> I have considered using another PHE to heat the store(particularly as
>>> my boiler is ideally supposed to work on sealled systems but will
>>> apparently work on vented if pressure sensor is disconnected). Thought
>>> this better than coil as can be cleaned easily if necessary. Also I
>>> assume order of efficiency is coil,PHE and best is heat store direct.
>>
>> Another PHE would do the trick quite nicely. While these are not cheap,
>> you would not need such a large one for this application since the boiler
>> power is the limiting factor here. You may even save equal or more money
>> by not needing an expensive cylinder with fast recovery coil. (any direct
>> tank could be used). Water to water PHEs are quite efficient so you would
>> not loose much if anything over pumping the primary through a direct
>> store.
>
> It is cheaper, far more efficient in economy, and far quicker using a
> plate heat X and bronze pump heating up a large direct cylinder. 95% plus
> of the boilers heat is extracted via the plate and put into the fresh
> water in the cylinder.
>
> Here is an off-the-shelf model:
> <http://www.mcdonald-engineers.com/products/plateflow.htm>
This also is a two-stage DHW delivery too. If he cylinder is exhausted of
heat it reverts to what the boiler gives like a combi. If no draw-off it
just re-heats the cylinder. So, even better performance from using a plate
rather than a coil.
i...@5roses.co.uk
> With the modern boiler, the most efficient way to get the high flow temp
> is to take advantage of a bigger delta T. If your boiler supports
> analogue control, then even better. You can select higher temps for
> replenishing the store, and much lower ones for running the heating
> (which is where you will probably spend most of your money - and so
> efficiency is of greatest importance).
If it makes any difference, some of the specs from the boiler manual
are:
Max heat o/p Qmax(80°/60°C) = 28KW
Min heat o/p Qmax(80°/60°C) = 5.6KW
Max heat o/p (50°/30°C) = 29.7KW
Min heat o/p (50°/30°C) =6.1KW
Working efficiency at max o/p (80°/60°C) = 97.6%
Working efficiency at max o/p (50°/30°C) = 103.5%
Working efficiency at 30% max o/p (Average T=50°C) = 107%
Working efficiency at min o/p (80°/60°C) = 98.2%
Working efficiency at min o/p (50°/30°C) = 107%
Max heating temp = 90°C
Min heating temp = 20°C
If analogue control means it has a manual control knob to adjust heat
o/p then it has one for heating and one for DHW.
It also came with an outside probe (which I'm assuming is the
mentioned weather compensator). It says this must be fitted for
maximun efficiency.
Yes, I did mean that the most efficient method to heat store was
direct first, then PHE and lastly coil. I see that you believe that
using a PHE uses about 95% of boiler's output. If it is assumed that
directly heating store uses 100%, looks like there is not much in it
from that point of view. DPS were quoting me £75 inc VAT for PHE. Then
pump on top.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> Bob Mannix wrote:
>
>> On the other hand, DD's explanation for the blending valve seems plain
>> common sense and was part of my assumption. Also these thermal store
>> systems only work well (high hot water flow) if the primary side of the
>> PHE (and hence the store itself) is at a very high temperature
>> (75-90degC). This can only be achieved by subtracting the boiler's
>> maximum delta-T from the desired temperature and ensuring the answer is
>> used as the set point for the return water. The condensing efficiency
>> argument is irrelevant as the whole system won't work without the higher
>> than normal return temperature.
>
> The blending valve will indeed keep the boiler flow hotter (at least in
> the early recovery stages after heavy demands have been made on the store,
> and assuming you have very well controlled stratification in the store),
> but there are many interacting variables and trade-offs here.
Chav, what might they be?
> These are at their most complex with a directly heated store since you
> can't control the heating load presented to the boiler as easily.
You can't? New to me. The heat load for the boiler is very predictable
indeed and the boiler runs in an ideal hydraulic environment.
> It is worth bearing in mind that this design is being proposed for use
> with a modern modulating, condensing boiler that supports wide temperature
> deltas.
Which means it is very suitable for a heat bank indeed and will promote
condensing.
> The whole "thermal store with everything hung off it" design concept is
> very well suited to older boiler designs where long burns, reduced
> cycling, high flow temps (and maintained above a threshold return temps)
> are all "good things".
..and well suited for modern condensing boilers too operating at lower
temperatures and wider delta Ts.
> Hence you have a nice "rule of thumb" solution to a number of problems.
We do? Prey tell....
> The whole situation is much less clear cut here.
It is...let us hear...
> Dribble is right that running rads from the store will let them run at low
> powers, which was a big gain when the alternative was 20kW or nothing and
> a mechanical stat overseeing the outer loop control. When the choice is
> anything from 7[1] to 28kW or nothing and tighter outer loop control, you
> are not going to notice much difference in a typical house with a few kW
> of heat losses.
7 kW is 25,000 btu/hr which is afair amount of heat injected into a heating
system that may only require 0.5kW (1,500 BTU/hr). This will result in
boiler cycling. And as most boioer only go to around 10 kW minimum the
problems is well...a big problem.
> ([1] number picked at random - I don't know how low the OPs boiler will
> modulate).
>
> Higher store temps are obviously good from an overall energy density point
> of view,
..good observation.
> but less good from a condensing efficiency one. The temperature you set
> for your hot water take off also has a big impact since it dictates how
> much headroom you have under the store temperature, and when falling store
> temperature will start to impact on the HW temperature. Opting for water
> at a temperature close to that of final use, and with less mixing at the
> point of use, will give more consistent water temperature output form the
> store with less worries about maintaining high and well stratified store
> temperatures.
..that mean a lower store setpoint and lower boiler return temperatures,
improving efficiency.
> With the modern boiler, the most efficient way to get the high flow temp
> is to take advantage of a bigger delta T. If your boiler supports analogue
> control, then even better. You can select higher temps for replenishing
> the store,
..yes...and...
> and much lower ones for running the heating (which is where you will
> probably spend most of your money - and so efficiency is of greatest
> importance).
You can do this with the store, have the DHW section at a higher temperature
than the CH section which can be controlled via an outside weather
compensator.
Taking the rads off the boiler direct with TVRs all around is a poor
substitute with great setbacks. As one rad needs to be controlled by a wall
stat and the auto by-pass will lower efficiency greatly by short circuiting
the boiler. The boiler needs to be complex and may have a short life
because of low flows through the heat exchanger (in a poor hydraulic
environment) and constant off switching when on part load (boiler cycling).
..and after I thought you were doing so well.
John Rumm
>> With the modern boiler, the most efficient way to get the high flow temp
>> is to take advantage of a bigger delta T. If your boiler supports
>> analogue control, then even better. You can select higher temps for
>> replenishing the store, and much lower ones for running the heating
>> (which is where you will probably spend most of your money - and so
>> efficiency is of greatest importance).
>
>
> If it makes any difference, some of the specs from the boiler manual
> are:
>
> Max heat o/p Qmax(80°/60°C) = 28KW
> Min heat o/p Qmax(80°/60°C) = 5.6KW
> Max heat o/p (50°/30°C) = 29.7KW
> Min heat o/p (50°/30°C) =6.1KW
That is a nice wide modulation range, which is good. When you subtract
the heat loss of the house from the lower figure it probably means that
the boiler can run the rads from almost no nett input which is ideal.
> Working efficiency at max o/p (80°/60°C) = 97.6%
> Working efficiency at max o/p (50°/30°C) = 103.5%
> Working efficiency at 30% max o/p (Average T=50°C) = 107%
> Working efficiency at min o/p (80°/60°C) = 98.2%
> Working efficiency at min o/p (50°/30°C) = 107%
> Max heating temp = 90°C
> Min heating temp = 20°C
>
>
> If analogue control means it has a manual control knob to adjust heat
> o/p then it has one for heating and one for DHW.
That will probably just be the flow temperature cut off stat....
I was thinking more along the lines of the type that can signal the
actual temperature to the boiler, rather than just a call for heat.
> It also came with an outside probe (which I'm assuming is the
> mentioned weather compensator). It says this must be fitted for
> maximun efficiency.
Ah, now that probably does present you with a control that will allow
you to something useful, i.e. arranging a higher flow temperature when
replenishing the store, and usually lower for the rads.
> Yes, I did mean that the most efficient method to heat store was
> direct first, then PHE and lastly coil. I see that you believe that
> using a PHE uses about 95% of boiler's output. If it is assumed that
> directly heating store uses 100%, looks like there is not much in it
> from that point of view. DPS were quoting me £75 inc VAT for PHE. Then
> pump on top.
The efficiency loss with the PHE is only only one of recovery time since
the boiler can modulate...
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> i...@5roses.co.uk wrote:
>>> With the modern boiler, the most efficient way to get the high flow temp
>>> is to take advantage of a bigger delta T. If your boiler supports
>>> analogue control, then even better. You can select higher temps for
>>> replenishing the store, and much lower ones for running the heating
>>> (which is where you will probably spend most of your money - and so
>>> efficiency is of greatest importance).
>>
>>
>> If it makes any difference, some of the specs from the boiler manual
>> are:
>>
>> Max heat o/p Qmax(80°/60°C) = 28KW
>> Min heat o/p Qmax(80°/60°C) = 5.6KW
>> Max heat o/p (50°/30°C) = 29.7KW
>> Min heat o/p (50°/30°C) =6.1KW
>
> That is a nice wide modulation range, which is good. When you subtract the
> heat loss of the house from the lower figure it probably means that the
> boiler can run the rads from almost no nett input which is ideal.
5.6 to 6.1 kW is high when the house is up to temp and one TRV opens
slightly.
Doctor Drivel
<i...@5roses.co.uk> wrote in message
news:a11d8bda-8a52-4592...@d4g2000prg.googlegroups.com...
> I note on your schematic you had a blending valve on the boilers return.
> Presumably to maintain a minimum return temperature. While this is
> common practice where one wants to prevent an older design of boiler
> from seeing excessive periods of low return temperatures, it would be
> counter productive on a condensing boiler since there is no requirement
> to maintain a minimum return temperature. Artificially raising the
> apparent return temperature when cooler water is available would just
> lower the boilers condensing efficiency. It also adds an extra tapping
> to the top of the tank and associated pipework.
Blending valve added as it was suggested on the original thread that
the temperature difference between the boiler flow and return should
be around the 20 deg mark to allow optimum condensing. To be fair,
when I asked DPS for a quote, they included a blending valve too on
their spec. In fact they said it should be a 28mm version for boilers
of >20KW as the internal parts on a 22mm were too small.
What makes and models are DPS using?
i...@5roses.co.uk
>
> Blending valve added as it was suggested on the original thread that
> the temperature difference between the boiler flow and return should
> be around the 20 deg mark to allow optimum condensing. To be fair,
> when I asked DPS for a quote, they included a blending valve too on
> their spec. In fact they said it should be a 28mm version for boilers
> of >20KW as the internal parts on a 22mm were too small.
>
> What makes and models are DPS using?
According to their spec, Reliance Water Controls (RWC) Heatguard
see http://www.rwc.co.uk/Product.aspx?page=CAT1
If you load the Panex tool and go to the Designer then click on the
green help bar to the right of the "No GX Primary" option, it brings
up about the GX circuit. Last paragraph says about the mixers and if
you click on "valve Sizing", gives you a graph.In fact if you click on
any of the green bars and then click on the Next and Prev buttons at
the top left corner, it gives a good explaination of the Pandora and
GX systems.
Thinking about the whole argument of the rads off or not off the
store, I guess new condensing boilers are designed largely to run rads
direct from boiler so it wouldn't be wrong and should be efficient
enough. However, the it is possible that more efficiency may or may
not be obtained feeding from the store. I guess neither is wrong and
looking at the big picture, there probably isn't much difference in
efficiency.
Doctor Drivel
<i...@5roses.co.uk> wrote in message
news:ab3c27af-ad9c-4469...@c23g2000hsa.googlegroups.com...
>
>>
>> Blending valve added as it was suggested on the original thread that
>> the temperature difference between the boiler flow and return should
>> be around the 20 deg mark to allow optimum condensing. To be fair,
>> when I asked DPS for a quote, they included a blending valve too on
>> their spec. In fact they said it should be a 28mm version for boilers
>> of >20KW as the internal parts on a 22mm were too small.
>>
>> What makes and models are DPS using?
>
> According to their spec, Reliance Water Controls (RWC) Heatguard
> see http://www.rwc.co.uk/Product.aspx?page=CAT1
>
> If you load the Panex tool and go to the Designer then click on the
> green help bar to the right of the "No GX Primary" option, it brings
> up about the GX circuit. Last paragraph says about the mixers and if
> you click on "valve Sizing", gives you a graph.In fact if you click on
> any of the green bars and then click on the Next and Prev buttons at
> the top left corner, it gives a good explaination of the Pandora and
> GX systems.
Thanks I had not looked into their latest additions.
> Thinking about the whole argument
> of the rads off or not off the
> store, I guess new condensing boilers
> are designed largely to run rads
> direct from boiler so it wouldn't be
> wrong and should be efficient
> enough.
New boilers are primarily designed for the replacement market and to mate up
with a system designed for 80 flow 70 return, temperature difference. More
heat can be delivered with a higher flow/return temp' difference. So a
condensing boiler may just do it at lower temperatures. The idea of burner
modulation (more complexity) is also to get the best efficiency out of the
system. Keston condensing boilers, up to about 5 years ago, were the most
simple boilers on the market - of any type. No pcb, no modulation, Super
simple and reliable. When these when connected to thermal stores/heat banks
they were the ultimate.
> However, the it is possible that more
> efficiency may or may not be obtained
> feeding from the store. I guess neither
> is wrong and looking at the big picture,
> there probably isn't much difference in
> efficiency.
One is better than the other and that is CH from the store, especially when
zoning. There is no central wall room stat to screw up the heat distribution
to the rooms, and heat can be injected to the rads from 0kW to the max they
can take.
The problem when using TRVs all around is the auto by-pass, these really
drop the efficiency when the house reaches temperature. ....and that is when
they are set properly, which 90% plus are not. Also, they are responsible
for many heat exchangers burning out as when not set properly or when they
run out of setting with wear, as they may restrict flow through the heat
exchanger. Best avoid that situation entirely if you can .....and you
can!!!!!!
Having the boiler operate at the optimum efficiency when re-heating the
store, you should really aim for too. And having the boiler only heat the
store this can be achieved.
As you are implementing a heat bank it is best take the two CH zones off the
store, and get the best system available. The cost is minimal for little
outlay.
John Rumm
> not be obtained feeding from the store. I guess neither is wrong and
> looking at the big picture, there probably isn't much difference in
> efficiency.
Therein is the rub. Will that small difference pay for the extra
hardware required, and extra installation time taken to include the rads
fed from the store (assuming the difference is even working in your
favour)?
You also need to think about how you will include a boiler interlock (a
building regs requirement) that stops the boiler firing once the house
is to temperature. Monitoring the store temperature alone is unlikely to
do this well enough.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> i...@5roses.co.uk wrote:
>
>> not be obtained feeding from the store. I guess neither is wrong and
>> looking at the big picture, there probably isn't much difference in
>> efficiency.
>
> Therein is the rub. Will that small difference pay for the extra hardware
> required, and extra installation time taken to include the rads fed from
> the store (assuming the difference is even working in your favour)?
Oh my God. The ramblings of an amateur. The difference is large. A modern
low capacity water content boiler connected to a TRV rad system is a
compromise. And it has serious setbacks too. Read what I write..it is much
easier that way.
> You also need to think about how you will include a boiler interlock (a
> building regs requirement) that stops the boiler firing once the house is
> to temperature. Monitoring the store temperature alone is unlikely to do
> this well enough.
He has TRVs all around. They close down when the house is up to temperature.
Then when the heat store is up to temp it switches out the boiler. The boier
is not firing when the hosue is up top temp. Got it? I doubt it.
John Rumm
>>> not be obtained feeding from the store. I guess neither is wrong and
>>> looking at the big picture, there probably isn't much difference in
>>> efficiency.
>>
>> Therein is the rub. Will that small difference pay for the extra
>> hardware required, and extra installation time taken to include the
>> rads fed from the store (assuming the difference is even working in
>> your favour)?
>
> Oh my God. The ramblings of an amateur.
Must you? oh go on then, ramble away...
> The difference is large.
Would you care to define "large"? Given that we are talking about a
boiler with a SEDBUK rating in excess of 90% here - a rating that is
based on a model that includes seasonal adjustment, typical control and
usage patterns in a domestic environment, and many other "real world"
factors. The scope for "large" would seem to be only for very small
values of "large"
(remember that that 100%+ efficiency values you think you can get do not
actually happen with the physics we use in this world).
> A modern low capacity water content boiler connected to a TRV rad system
> is a compromise.
What, being used in the way it was designed to be operated?
Hmmm....
> And it has serious setbacks too. Read what I
> write..it is much easier that way.
Actually reading what you write is never easy. You border on functional
illiteracy much of the time, and much of the rest is parrot like
repetition of other cruft.
>> You also need to think about how you will include a boiler interlock
>> (a building regs requirement) that stops the boiler firing once the
>> house is to temperature. Monitoring the store temperature alone is
>> unlikely to do this well enough.
>
> He has TRVs all around. They close down when the house is up to
> temperature. Then when the heat store is up to temp it switches out the
> boiler. The boier is not firing when the hosue is up top temp. Got it?
Even with the large phase lag you introduced with the store huh?
A non TMV equipped rad and a programmable thermostat (per zone) will do
a better job and make for more practical comfort.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> Doctor Drivel wrote:
>
>>>> not be obtained feeding from the store. I guess neither is wrong and
>>>> looking at the big picture, there probably isn't much difference in
>>>> efficiency.
>>>
>>> Therein is the rub. Will that small difference pay for the extra
>>> hardware required, and extra installation time taken to include the rads
>>> fed from the store (assuming the difference is even working in your
>>> favour)?
>>
>> Oh my God. The ramblings of an amateur.
>
> Must you? oh go on then, ramble away...
>
>> The difference is large.
>
> Would you care to define "large"? Given that we are talking about a boiler
> with a SEDBUK rating in excess of 90% here - a rating that is based on a
> model that includes seasonal adjustment, typical control and usage
> patterns in a domestic environment, and many other "real world" factors.
> The scope for "large" would seem to be only for very small values of
> "large"
I have explained the difference enough re-read.
> (remember that that 100%+ efficiency values you think you can get do not
> actually happen with the physics we use in this world).
That does explain ignorance.
>> A modern low capacity water content boiler connected to a TRV rad system
>> is a compromise.
>
> What, being used in the way it was designed to be operated?
Oh my God! He can't even get that either. A compromise in design and
application.
>>> You also need to think about how you will include a boiler interlock (a
>>> building regs requirement) that stops the boiler firing once the house
>>> is to temperature. Monitoring the store temperature alone is unlikely to
>>> do this well enough.
>>
>> He has TRVs all around. They close down when the house is up to
>> temperature. Then when the heat store is up to temp it switches out the
>> boiler. The boier is not firing when the hosue is up top temp. Got it?
>
> Even with the large phase lag you introduced with the store huh?
Nah! You didn't get it.
> A non TMV equipped rad and a programmable thermostat (per zone) will do a
> better job and make for more practical comfort.
You don't know waht you are prattling about!!!!! Never did.
Doctor Drivel
> (remember that that 100%+ efficiency values you think you can get do not
> actually happen with the physics we use in this world).
Chav, they happen in the heating world. From Mikrofill:
"This ETHOS; is a high efficiency, condensing, combination Boiler. Flues are
cooled below condensation point by a Spiranox heat exchanger made of
stainless steel. This produces an additional heat which will contribute to
the boiler
efficiency, which is in excess of 107%. The European calculation method
assumes 100% efficiency for appliances which do not condense and
efficiencies higher than 100% for condensing appliances. "
<http://www.mikrofill.co.uk/images/PDF/54-technical.pdf>
Chav, notice the 107%. Still to lecky sockets.
John Rumm
Yes I notice.
Did you notice the "The European calculation method
assumes 100% efficiency for appliances which do not condense and
efficiencies higher than 100% for condensing appliances."?
This tells you that the method of calculation is flawed, and it will
yield a nonsensical answer. If you deliberately under specify the energy
content of the fuel when performing the calculation, but accurately
measure the heat output, you may well get a calculated efficiency of
over 100%. This does not mean that actual efficiency is over 100%, just
you have demonstrated GIGO yet again.
Let me make this quite clear for you. No combi boiler, condensing or
otherwise is going to violate the laws of conservation of energy.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> Doctor Drivel wrote:
>> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>> news:13o5ea4...@corp.supernews.com...
>>
>>> (remember that that 100%+ efficiency values you think you can get do not
>>> actually happen with the physics we use in this world).
>>
>> Chav, they happen in the heating world. From Mikrofill:
>>
>> "This ETHOS; is a high efficiency, condensing, combination Boiler. Flues
>> are cooled below condensation point by a Spiranox heat exchanger made of
>> stainless steel. This produces an additional heat which will contribute
>> to the boiler efficiency, which is in excess of 107%. The European
>> calculation method assumes 100% efficiency for appliances which do not
>> condense and efficiencies higher than 100% for condensing appliances. "
>>
>> <http://www.mikrofill.co.uk/images/PDF/54-technical.pdf>
>>
>
> Yes I notice.
>
> Did you notice the "The European calculation method
> assumes 100% efficiency for appliances which do not condense and
> efficiencies higher than 100% for condensing appliances."?
Chav, yes, I did.
> This tells you that the method of calculation is flawed,
It isn't it is just a method.
> and it will yield a nonsensical answer.
It doesn't.
> If you deliberately under specify the energy content of the fuel when
> performing the calculation, but accurately measure the heat output, you
> may well get a calculated efficiency of over 100%. This does not mean that
> actual efficiency is over 100%, just you have demonstrated GIGO yet again.
>
> Let me make this quite clear for you. No combi boiler, condensing or
> otherwise is going to violate the laws of conservation of energy.
None do.
frank...@hotmail.co.uk
would like some advice.
A comment by Dr Drivel in the summer got me thinking:
'This is where a thermal store comes in. Take all the zones from the
water
store and the boiler only heats the store with one long efficient
burn.'
I'm renewing the boiler and propose to use a combi as a replacement.
For HW I'm happy with the flow rate this will give. We use modest
amounts of hot water don't need a big store in reserve.
The CH is another matter - it is where way most of the energy goes. I
want to zone each room because of the number we don't use all the time
and the variable use throughout the day: Guest rooms, second
bathrooms, daytime office, first floor lounge only used in the evening
and so on. Our use is pretty predictable so thermostat timers in the
rooms and valves on a central flow and return tree going up the middle
of the house will work fine I think
Now that could, of course, all be wired into the boiler as it is
modulating and has an adjustable bypass valve. But I wondered if it
might be better to have the boiler heating up a cylinder which could
be placed in a cupboard in the heart of the house (It's a three storey
terrace) where no boiler could ever go. Then use the cylinder as a
heat store to feed the central heating.
Separpate pump required of course but I'm attracted by:
Boiler has a very simple job to do and can be carefully controlled.
Nice clean water with no radiator bits going through the heat
exchanger
Pair of thermostats and a latching relay on they cylinder to widen the
on/off temperature to stop the boiler topping up the store too quickly
when the load is small
Possibility to time the heating of the store in, say, the morning
before a demand for DHW so that the CH continues to function when bath/
shower running.
Possibility of electric immersion back-up for limited CH if boiler
breaks down
Downsides (and this is where I hope folks will help me the most):
Might be needlessly complicated
More expensive
Maybe unfeasable or inefficient for reasons I haven't anticipated.
For instance I imagine using a conventional rapid recovery copper
cylinder of a suitable size with indirect connection to the boiler and
the CH flowing through the (vented) cylinder. But I've a feeling that
might be a little inefficient though necessary to get enough flow to
the radiators. Or am I straying badly off piste here?
I haven't complicated things further by considering the use of heat
exchangers as yet but would welcome suggestions.
I look forward to hearing folks views. I want to get this right and
good information is hard to find so please help as much as you can.
Regards,
Frank
Doctor Drivel
<frank...@hotmail.co.uk> wrote in message
news:8a0d61dc-ca9f-4c49...@s8g2000prg.googlegroups.com...
A snippet. Yes, a CH buffer is the best way. For each room have a Wilo
Smart pump at £44 from Screwfix instead of zone valves. Simpler, more
reliable and better flow. A whole bank of them neatly on the wall. Have a
header off the cylinder of 28mm pipe and take all the pumps off this. Or if
possible two headers, upstairs and downstairs.
A boiler can go inside the house not on an outside wall. Look at the Keston
which can have 60 foot of cheap plastic waste pipe for the flue.
Frank, a bit late so I will get back to you tomorrow. You appear a bright
man.
frank...@hotmail.co.uk
> <frankfr...@hotmail.co.uk> wrote in message
>
> news:8a0d61dc-ca9f-4c49...@s8g2000prg.googlegroups.com...
>
>
>
> > I've not posted here before but have been following the discussion and
> > would like some advice.
>
> > A comment by Dr Drivel in the summer got me thinking:
>
> > 'This is where a thermal store comes in. Take all the zones from the
> > water
> > store and the boiler only heats the store with one long efficient
> > burn.'
>
> > I'm renewing the boiler and propose to use a combi as a replacement.
> > For HW I'm happy with the flow rate this will give. We use modest
> > amounts of hot water don't need a big store in reserve.
>
> > The CH is another matter - it is where way most of the energy goes. I
> > want to zone each room because of the number we don't use all the time
> > and the variable use throughout the day: Guest rooms, second
> > bathrooms, daytime office, first floor lounge only used in the evening
> > and so on. Our use is pretty predictable so thermostat timers in the
> > rooms and valves on a central flow and return tree going up the middle
> > of the house will work fine I think
>
> > Now that could, of course, all be wired into the boiler as it is
> > modulating and has an adjustable bypass valve. But I wondered if it
> > be placed in a cupboard in the heart of the house (It's a three storey
> > terrace) where no boiler could ever go. Then use thecylinderas a
>
> > Separpate pump required of course but I'm attracted by:
>
> > Boiler has a very simple job to do and can be carefully controlled.
> > Nice clean water with no radiator bits going through theheat
> > exchanger
> > on/off temperature to stop the boiler topping up the store too quickly
> > when the load is small
> > Possibility to time the heating of the store in, say, the morning
> > before a demand for DHW so that the CH continues to function when bath/
> > shower running.
> > Possibility of electric immersion back-up for limited CH if boiler
> > breaks down
>
> > Downsides (and this is where I hope folks will help me the most):
>
> > Might be needlessly complicated
> > More expensive
> > Maybe unfeasable or inefficient for reasons I haven't anticipated.
> > For instance I imagine using a conventional rapid recovery copper
> > the CH flowing through the (vented)cylinder. But I've a feeling that
> > might be a little inefficient though necessary to get enough flow to
> > the radiators. Or am I straying badly off piste here?
> > I haven't complicated things further by considering the use ofheat
> > exchangers as yet but would welcome suggestions.
>
> > I look forward to hearing folks views. I want to get this right and
> > good information is hard to find so please help as much as you can.
>
> > Regards,
>
> A snippet. Yes, a CH buffer is the best way. For each room have a Wilo
> Smart pump at £44 from Screwfix instead of zone valves. Simpler, more
> header off thecylinderof 28mm pipe and take all the pumps off this. Or if
> possible two headers, upstairs and downstairs.
>
> A boiler can go inside the house not on an outside wall. Look at the Keston
> which can have 60 foot of cheap plastic waste pipe for the flue.
>
> Frank, a bit late so I will get back to you tomorrow. You appear a bright
> man.
Dr Drivel
Thank you for getting back. Very encouraging.
I want to end up with a system that is as low on wasted energy as is
compatible with a high level of convenience and flexibility. (So no
surprise there then.) Of course this has to be balanced by an
increase capital outlay and time (my time so 'free' ha ha) for
installing. I can swallow a bit of a capital hit as the present set
up seems designed for maximum inefficiency. I hope to make good
savings.
I'll try to describe what I plan as fully as possible to help you make
further suggestions.
The house is a stone terraced mid Victorian thing on three floors in
Edinburgh. There is a central stairwell going the full height in the
middle. The foot-print isn't huge but I reckon ten zones:
G/F
1) Stairwell - full height so thermostat placement will be in
interesting one.
2) My office (I work from home),
3) Kitchen & main living area inc. D/S loo and utility room (I thought
of putting the utility on a trv as it will need to be on all the time
that Zone 3 is but not as warm).
F/F
4) Master bedroom
5) Child's room
6) Lounge
7) Bathroom
T/F
8) Guest Room
9) Bathroom plus small second guest room on TRV
10) Wife's study
Every one of the is Zones is justified by need according to the
criteria of 1) need to be on at different and nearly always predicable
times during the day/week and/or 2) benefit form individual
temperature control.
Of course all this assumes that he doors are kept closed and the inter-
room insulation is reasonable. This is the case I think except
possibly for Junior's bedroom door... (Nurse! the electrodes please.)
I plan to put the boiler on the second floor (in a cupboard off the
small guest room/store) where it is well placed for flue exit and
access. This location is directly above the first floor bathroom and
almost adjacent to the second floor bathroom so good for HW delivery.
The run from the boiler to the CH cylinder would also be fine from
here with plenty of space for good insulation of the flow and
return. the compact nature of the dwelling means that no zone is
very far from the central nest of control valves or pumps as you
suggest.
Okay a few specifics.
I'm thinking in favour of the Vaillant 937 boiler. As I'm sure you
know this had the 15l heatstore in it and blends the outflow to
produce rapid HW in at high pressure in good quanities. We don't use
much HW so what we do use must be instant and plentiful. The extra
cost of the heatstore thing in the Vaillant can be reduced by having
smallish timed windows when it is got up to and kept at running
temperatuire by the boiler. It is well insulated and blends even when
it has cooled down a bit so if it is poised and ready to go twice a
day for about an hour to coincide with morning ablutions and long-hot-
soaks I think we should be fine. Experience will tell if this has to
be altered much when we have guests.
It's a 28kw boiler I think so not over large but quite big enough to
run the CH via a heat store.
My expectation is that the extra cost of keeping the heatstore hot
will be almost irrelevant due to the low amount of HW used and the far
greater expense of the CH. The 937 is about 1K trade so is not cheap
for a modest sized combi. I think the benefits are worth the outlay.
Once again other folks experience here would be appreciated.
The roof is well insulated with Tri-Iso and I intend having a generous
CW storage tank. Whilst the CW to the shower mixer will have to be
from the mains the CW to the baths, basins and loos can be from the
tank. As I see it the advantages are:
Warmer cold water so bigger bath for your money; more comfortable when
washing hands etc; loo cystern won't drip condensate. Added to this
if the tank is a reasonable size then it ca be set to refill quite
slowly and thus reduce thepressure drop of incoming mains at a time
when that might be most needed. If the tank refills slowly there
should be no chance of a tedious whistling of the pipes.
I wonder in no particular order:
1) What type and size of cylinder I should use for the CH heat store
and exactly how it should be configured. I'm not sure putting the
return in at the base is best as quiet warm water would hit cold water
and so total mixing rather that stratifying w
2) Whether to use the wilo smart pumps or valves for the zoning.
Pump noise would drive me bonkers. Obviously if I use the valves
there will be at least one pump. Certainly the valves are likely to
break down and need replacing earlier but they are a bit cheaper.
Wilos are supposed to be very quiet though...
I'll probably need to try one and see. They could be carefully
mounted and vibration insulated. Some of the zones are only be one
radiator and mostly microbore. Whooshing we don't need. Will the
lowest speed be low enough? The pumps will have valves either side
for servicing so the flow cold be restricted but then that puts the
pump under more strain. I'd be interested to know what people think
about this.
Finally - For now - thre is an anomaly in the system. The Kitchen is
about as far as it can get from the boiler. The Vaillant boasts about
15l per min flow. in 15mm pipe allowing a but for resistance I reckon
on better than a meter per second. It's 18m to the kitchen. Do I
want to wait 15-18s for HW? I think I might put a small Santon 10l
mains pressure electric aquaflow under the sink. Bigger outlay but
could be on a timer to warm once or twice a day and mains pressure HW
would be there instantly in the small quantities needed without waking
the boiler up. Amazing how much less HW we use at the sink once a
dishwasher is dong it's thing.
As an aside I tend to plumb DW and washing machine in with just a cold
supply.
The under sink Santon could easily be retrofitted if HW from the
boiler was found to be unsatisfactory.
Okay. Thanks for reading. I look forward to Dr Drivel and other
folk's comments and suggestions.
Regards to all,
Frank
Doctor Drivel
news:83906828-e2df-40fa...@e10g2000prf.googlegroups.com...
> I plan to put the boiler on the second
> floor (in a cupboard off the small guest
> room/store) where it is well placed for
> flue exit and access. This location is
> directly above the first floor bathroom and
> almost adjacent to the second floor bathroom
> so good for HW delivery. The run from the
> boiler to the CH cylinder would also be fine from
> here with plenty of space for good insulation
> of the flow and return. the compact nature
> of the dwelling means that no zone is
> very far from the central nest of control valves
> or pumps as you suggest.
> Okay a few specifics.
> I'm thinking in favour of the Vaillant 937 boiler.
> As I'm sure you know this had the 15l heatstore
> in it and blends the outflow to produce rapid
> HW in at high pressure in good quanities. We don't use
> much HW
Frank,
The first approach I would look at is a heat bank/thermal store heated by a
Glow Worm HXi vented "heating" boiler, not a combi.
http://tinyurl.com/2p279m
The 24 kW version is £638.03 Including VAT at 17.5% Made by Vaillant. It
is small in size. A set speed pump is needed to heat the heat bank
cylinder.
This give a CH buffer and instant mains presure DHW.
Look at:
http://www.rangecylinders.co.uk/products/flowmax/models/cylinder/
The 200 litre model.
As the cylidner is central in the house with rads above it, an F&E tank must
go inthe loft.
Your zones.
You can have simple cheap timeclocks in bank in a central location, saving
on clock/stats, so all the rooms can be set and switched on or off without
running around the house. And have one master time clock to switch all of
the system off, so the 10 timeclocks are slaves. to the master clock. Have
TRVs on each rad then. No wall stats needed. The Wilo Smart pump will
automatically run up and down speed depending on pressure. If all TRVs on
one zone are closed, or near closed, it runs down. Most of the time the
pump is at reduced speed saving power and reduced noise. If all are fully
off the pump is off, well runs very slowly. They are quiet. They have
three settings, probably setting 1 is fine for all but one zone. If one rom
only need 0.25 kW of heat the Smart pump just gently injects it into the
rad(s). Get good quality full bore rad valves, then no restriction.
Cost per zone using a Smart pump, TRV and simple time clock is about the
same as a clock/stat and 2-port zone valve (only use "good" quality zone
valves and they are not cheap).
Pump/zone headers:
Off the heat bank cylinder have a 28mm header pipe out of the flow tapping
and tee off all zone pumps from this. A check valve after each pump. The
same for the return, a 28mm return header with all return pipes teed into
this. I would put a full bore 12/4 turn isolating valve here so the whole
zone can be isolated and drained to avoid a full drain down.
Have a Magnaclean filter on the return to thye cylinder. Make sure enough
inhibitor is in the system.
So you have:
- one heat bank cylinder giving DHW and CH buffer.
- one simple vented boiler
- centralised time control (you can have the odd one local in a room if
neede be).
- No by-pass needed.
- small boiler. The 937 is the size of a washing machine.
- more reliable temperature control
- more reliable zoning using a pump.
- more reliable simple boiler.
- buffering of CH.
- no Boiler cycling.
- reduced size boiler as a thermal storage system only needs the boiler to
be sized for avearge use, not peak use.
In the morning when CH come in, not all zones at the same time it appears,
the rads are heated instantly as the water is dumped into the rads from the
cylinder. The boiler comes in re-heats at full belt. The rads then do not
require full heat from the cylinder and DHW can be served quite easily.
John Rumm
> I'll try to describe what I plan as fully as possible to help you make
> further suggestions.
>
> The house is a stone terraced mid Victorian thing on three floors in
> Edinburgh. There is a central stairwell going the full height in the
> middle. The foot-print isn't huge but I reckon ten zones:
> G/F
> 1) Stairwell - full height so thermostat placement will be in
> interesting one.
> 2) My office (I work from home),
What sort of equipment do you have in here, other than you?
> 3) Kitchen & main living area inc. D/S loo and utility room (I thought
> of putting the utility on a trv as it will need to be on all the time
> that Zone 3 is but not as warm).
>
> F/F
> 4) Master bedroom
> 5) Child's room
> 6) Lounge
> 7) Bathroom
>
> T/F
> 8) Guest Room
> 9) Bathroom plus small second guest room on TRV
> 10) Wife's study
>
> Every one of the is Zones is justified by need according to the
> criteria of 1) need to be on at different and nearly always predicable
> times during the day/week and/or 2) benefit form individual
> temperature control.
I would question whether you will ever reap any return on the cost and
complexity of system required to support this number of zones. Remember
that individual temperature control in a room can be achieved via its TRV.
Before going much further in this you need to do some detailed heat loss
calculations for the building. Once these are done you can factor in the
effect of leaving particular rooms unheated, and see how that changes
the overall heat loss picture (and hence running costs).
I expect you will find that the difference between 10 zones and say
three (e.g. "all day" spaces, evening spaces, sleeping spaces), will be
negligible in terms of difference in running costs and day to day comfort.
> I plan to put the boiler on the second floor (in a cupboard off the
> small guest room/store) where it is well placed for flue exit and
> access. This location is directly above the first floor bathroom and
> almost adjacent to the second floor bathroom so good for HW delivery.
> The run from the boiler to the CH cylinder would also be fine from
> here with plenty of space for good insulation of the flow and
> return. the compact nature of the dwelling means that no zone is
> very far from the central nest of control valves or pumps as you
> suggest.
Have you thought about what your hot water requirements are? i.e.
showers, baths, one or two at a time?
Have you established if your mains supply is capable of meeting your hot
water requirements on demand without any storage facility?
>
> Okay a few specifics.
>
> I'm thinking in favour of the Vaillant 937 boiler. As I'm sure you
> know this had the 15l heatstore in it and blends the outflow to
> produce rapid HW in at high pressure in good quanities. We don't use
> much HW so what we do use must be instant and plentiful. The extra
"Don't user much", and must be "plentiful" sound like contradictory
requirements. Could you clarify?
> The roof is well insulated with Tri-Iso and I intend having a generous
That's the multi foil stuff?
> CW storage tank. Whilst the CW to the shower mixer will have to be
> from the mains the CW to the baths, basins and loos can be from the
> tank. As I see it the advantages are:
Why mains to the shower mixer if you are planning to run gravity hot?
> Warmer cold water so bigger bath for your money; more comfortable when
Not really... where does the heat come from that warms the cold water?
You pay for it all in the end.
> 1) What type and size of cylinder I should use for the CH heat store
> and exactly how it should be configured. I'm not sure putting the
> return in at the base is best as quiet warm water would hit cold water
> and so total mixing rather that stratifying w
You need to do the heatloss calcs first to have any idea.
> Finally - For now - thre is an anomaly in the system. The Kitchen is
> about as far as it can get from the boiler. The Vaillant boasts about
> 15l per min flow. in 15mm pipe allowing a but for resistance I reckon
> on better than a meter per second. It's 18m to the kitchen. Do I
> want to wait 15-18s for HW? I think I might put a small Santon 10l
> mains pressure electric aquaflow under the sink. Bigger outlay but
> could be on a timer to warm once or twice a day and mains pressure HW
> would be there instantly in the small quantities needed without waking
> the boiler up. Amazing how much less HW we use at the sink once a
> dishwasher is dong it's thing.
If you are going for HW from a thermal store then it would be simple to
implement a secondary circulation loop for the sink. That would ensure
instant hot water there.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> Why mains to the shower mixer if you are planning to run gravity hot?
He is not running gravity hot.
>> Warmer cold water so bigger bath for your money; more comfortable when
>
> Not really... where does the heat come from that warms the cold water? You
> pay for it all in the end.
Solar gain the loft can make an effect.
> If you are going for HW from a thermal store then it would be simple to
> implement a secondary circulation loop for the sink. That would ensure
> instant hot water there.
Some sense here at last.
frank...@hotmail.co.uk
I take on board what Dr Drivel and JR have to say.
I like the idea of using a more basic boiler and a vented system. All
very doable and simple to fix when it goes wrong.
Not sure I fancy paying Range or a similar company that much for
putting a PHE inside a copper cylinder.
Is there any reason why an external PHE with a circulating pump and
flow switch could not be fitted for those things that demand mains
pressure HW? This would be a shower and possibly the top floor
bathroom. I've seen some designs elsewhere for a diy set up and folk
saying that a 100kw PHE can be had for a bout £100.
Of course I would be demanding a lot from the cylinder. It would have
to be a thermal store (rather than a heat bank if I have understood
the nomenclature correctly) for the CH as well as for HW via gravity
or the PHE.
I assume the cylinder would be heated indirectly by the boiler and the
PHE take off would be at the very top with the CH flow and return
lower down. I can see that there might be issues with loss of
stratification when the CH is cranking away but perhaps with clever
timing of the initial CH burst in the morning to a limited number of
zones and then a re-heat to prepare for ablutions the set up would
cope fine. The CH has a fair amount of inertia in it and the cylinder
could be of the rapid recovery type.
Modest sized indirect copper cylinders can be had reasonably cheaply
still so perhaps two smaller ones would be better with CH in one and
HW in the other. Would have a choice of direct/indirect in the HW one
then.
The other major expense is controlling all the zones. TRV + single
channel timer + pump(or valve) is going to be about £90 per zone.
There might be some scope for reducing the number of zones but it soon
gets wasteful.
On other thing. A heat store for the HW does mean that water is being
heated up that won't always be used. Not a problem so much in the
winter as the CH will be doing it's thing but in the summer it might
be wasteful though perhaps not much. One of the attractions of a
combi I suppose.
I am very interested to know what Dr Drivel and John Rumm as well as
anyone else has to say to these ideas.
In response to some of the other points:
1) Equipment in office making heat? Only a couple of laptops.
2) Mains flow/pressure: Inlet from street is lead into 15mm pipe.
15mm to top of house. At top of house is 4bar
Flow rate:
13lpm at 3.3bar
17lpm at 2.5bar
20lpm at 2.0bar
3) hot water demand? might be a shower and bath at same time now and
then.
4) Circulation loop to the kitchen. Thanks for that suggestion. What
factors would reduce heat loss other than lagging?
5) Warming up the cold water in tanks in the loft. Don't reckon I can
ever make the loft as cold as the incoming water temp in winter so I
hope to cash in on some of the inevitable heat loss from house into
this space. Warmer in summer of course.
Would be fun to think of a way of 'preheating' the mains water going
to the HW supply up here as well.
A degree or two would make all the difference would it not?
I sometimes wonder if the bath/shower waste couldn't be made to warm
up the incoming cold water on it's way to the street.
I look forward to further helpful comments and suggestions from one
and all. May I say again how much I appreciate the trouble Dr Drivel
and JR are taking?
Thanks
Frank
John Rumm
> I like the idea of using a more basic boiler and a vented system. All
> very doable and simple to fix when it goes wrong.
"basic" in the context of a modern boiler is a bit of a oxymoron. None
are exactly simple, and even the simplest will have extensive
electronics controlling its operation.
> Is there any reason why an external PHE with a circulating pump and
> flow switch could not be fitted for those things that demand mains
> pressure HW? This would be a shower and possibly the top floor
> bathroom.
No, not at all. Why would you want the HW supplied any other way?
> I assume the cylinder would be heated indirectly by the boiler and the
If have a vented primary circuit then you could heat it directly or
indirectly. Personally I favour a sealed primary, and hence would opt
for indirect heating of the store.
> PHE take off would be at the very top with the CH flow and return
> lower down. I can see that there might be issues with loss of
> stratification when the CH is cranking away but perhaps with clever
> timing of the initial CH burst in the morning to a limited number of
> zones and then a re-heat to prepare for ablutions the set up would
> cope fine. The CH has a fair amount of inertia in it and the cylinder
> could be of the rapid recovery type.
>
> Modest sized indirect copper cylinders can be had reasonably cheaply
> still so perhaps two smaller ones would be better with CH in one and
> HW in the other. Would have a choice of direct/indirect in the HW one
> then.
Or cut the complexity, go for a boiler with a decent modulation range,
and let the boiler drive the rads directly.
(dribble prefers his one size fits all solution using the store for
everything, as you can probably judge from the previous messages)
> The other major expense is controlling all the zones. TRV + single
> channel timer + pump(or valve) is going to be about £90 per zone.
> There might be some scope for reducing the number of zones but it soon
> gets wasteful.
I think when you do the heatloss calcs your will find there is little to
be gained by going beyond a handful of zones. If you leave a room
unheated then you just increase losses from the rooms that surround it,
and it ends up being heated indirectly anyway. You also would need to
work out how to plumb it. With lots of zones controlled from a central
location you are going to have masses of pipework, which aside from
being expensive to purchase, will require lots of install time and lots
of hacking about of the house.
If you really want lots of zones you may be better with a pair of
largish primary "backbone" pipes providing flow and return points for
each floor, and then teeing off them for the individual rooms / zones.
The zones could be enabled by valves (or pumps if you prefer) locally -
even if you take the control back to a central location.
> On other thing. A heat store for the HW does mean that water is being
> heated up that won't always be used. Not a problem so much in the
> winter as the CH will be doing it's thing but in the summer it might
> be wasteful though perhaps not much. One of the attractions of a
> combi I suppose.
If the store is well insulated it will make little difference. In the
winter any heat it looses will pass beneficially into the house anyway.
> In response to some of the other points:
>
> 1) Equipment in office making heat? Only a couple of laptops.
OK, not huge then. I tend to find that a couple of PCs running 24/7 is
usually enough extra heat to require very little input from the heating.
> 2) Mains flow/pressure: Inlet from street is lead into 15mm pipe.
> 15mm to top of house. At top of house is 4bar
> Flow rate:
> 13lpm at 3.3bar
> 17lpm at 2.5bar
> 20lpm at 2.0bar
So is 20 lpm the best flow rate you can get?
If so this negates some of the advantages of having a thermal store
arrangement for HW production since the supply would not be able to keep
up with multiple simultaneous users of the water even if the store could.
> 3) hot water demand? might be a shower and bath at same time now and
> then.
You may find a combi with its HW output feeding the shower, and a fast
recovery indirect cylinder on a zone on the heating side of the boiler
would meet that requirement better. Fast flow rate for the bath from the
cylinder, and high pressure for the shower from the mains, but without
over stretching the mains supply. (you could throttle the cold tank
replenishment rate if you have a largish tank)
> 4) Circulation loop to the kitchen. Thanks for that suggestion. What
> factors would reduce heat loss other than lagging?
If you can predict likely times for use, having a timer control on the
loop ought to achieve that. (you just need to accept that you will need
to run off some cold water and wait a bit should you use the tap at
other times). Failing that, if you do use a combi, then perhaps it can
supply the kitchen tap if not too far away.
> 5) Warming up the cold water in tanks in the loft. Don't reckon I can
> ever make the loft as cold as the incoming water temp in winter so I
> hope to cash in on some of the inevitable heat loss from house into
> this space. Warmer in summer of course.
Just take care not to insulate under them - you need a little heat loss
to stop them freezing.
> Would be fun to think of a way of 'preheating' the mains water going
> to the HW supply up here as well.
> A degree or two would make all the difference would it not?
All the difference to what?
> I sometimes wonder if the bath/shower waste couldn't be made to warm
> up the incoming cold water on it's way to the street.
Can be done - there is another thread running in the group on that at
the moment. It has also been discussed before.
i...@5roses.co.uk
Just got round to measuring flow rate and opening all cold taps at
once and measuring total quantity of water in 1 minute, it looks like
I have a flow rate of about 37L/min. Hopefully, that is pretty good.
As to pressure, don't have a guage for this but believe it to be very
strong. can't hold thumb over tap without water still spurting out
quite forcefully. (Very scientific I know but seem to remember someone
suggesting that once!)
Also checked existing pipework and as I currently have a combi,
pipework to bath is in 15mm. Is it necessary to upgrade it 22mm? Would
be bit of a pain if need to as bathroom all tiled etc. Would mean a
long route of going downstairs then back up again.
Doctor Drivel
<frank...@hotmail.co.uk> wrote in message
news:83a096fd-0f64-4154...@f47g2000hsd.googlegroups.com...
> Thanks for the above posts. I appreciate the effort.
> I take on board what Dr Drivel and JR have to say.
> I like the idea of using a more basic boiler and a vented system. All
> very doable and simple to fix when it goes wrong.
The HXIs are simple enough and well made.
> Not sure I fancy paying Range or a
> similar company that much for
> putting a PHE inside a copper cylinder.
It is outside, but follow the thread and you can make one yourself . I gave
instructions on how to do it. I will try to dig them out.
> Is there any reason why an external PHE
> with a circulating pump and flow switch could
> not be fitted for those things that demand mains
> pressure HW? This would be a shower and
> possibly the top floor bathroom.
You can do. What is wrong with putting the whole DHW on the plate heat X?
> I've seen some
> designs elsewhere for a diy set up and folk
> saying that a 100kw PHE can be had for a bout £100.
About £70 from DPS I hear. Gledhill will supply them as standard
replacement parts too, for around £80
> Of course I would be demanding a lot from
> the cylinder. It would have to be a thermal
> store (rather than a heat bank if I have understood
> the nomenclature correctly) for the CH as well
> as for HW via gravity or the PHE.
No. If you have a house that needs 24 to 27 kW for CH a 200 litre cylinder
will do CH and DHW. Find out the Kw requirements of the house (heat loss)
> I assume the cylinder would be heated
> indirectly by the boiler
No, directly
> and the PHE take off would be at the very
> top with the CH flow and return lower down.
Yep.
> I can see that there might be issues with loss of
> stratification when the CH is cranking away
> but perhaps with clever timing of the initial
> CH burst in the morning to a limited number of
> zones and then a re-heat to prepare for ablutions
> the set up would cope fine.
Install spreader pipes.
> The CH has a fair
> amount of inertia in it and the cylinder
> could be of the rapid recovery type.
Keep the cylinder direct it is more efficient.
> Modest sized indirect copper cylinders
> can be had reasonably cheaply
> still so perhaps two smaller ones would be
> better with CH in one and HW in the other.
> Would have a choice of direct/indirect in the HW one
> then.
The two could be heated directly by the one boiler. Two pumps or one pumps
and a 3-way "diverter valve. DHW has priority. When DHW calls its cylinder
gets all the boilers heat. Then it drop back to heating the CH cylinder.
> The other major expense is controlling
> all the zones. TRV + single
> channel timer + pump(or valve) is going
> to be about £90 per zone. There might be
> some scope for reducing the number of zones but it soon
> gets wasteful.
The more zones the more money - simple.
> On other thing. A heat store for the HW
> does mean that water is being
> heated up that won't always be used.
> Not a problem so much in the
> winter as the CH will be doing it's thing
> but in the summer it might be wasteful
> though perhaps not much. One of the
> attractions of a combi I suppose.
You could get a combi to match your DHW needs and then have a CH buffer
heated by the boiler using a fast recovery coil.
> In response to some of the other points:
> 1) Equipment in office making heat? Only a couple of laptops.
> 2) Mains flow/pressure: Inlet from street is lead into 15mm pipe.
> 15mm to top of house. At top of house is 4bar
> Flow rate:
> 13lpm at 3.3bar
> 17lpm at 2.5bar
> 20lpm at 2.0bar
Not startling at all.
> 3) hot water demand? might be a
> shower and bath at same time now and
> then.
You might want to consider an accumulator tank and a combi. The accumulator
is simple to fit - a tee into the mains pipe, anywhere on the cold water
mains. . Then high pressure and adequate flow and stored water backup if
water is off from street.
> 4) Circulation loop to the kitchen. Thanks
> for that suggestion. What factors would
> reduce heat loss other than lagging?
A time clock and a pipe stat.
> 5) Warming up the cold water in tanks
> in the loft. Don't reckon I can ever make
> the loft as cold as the incoming water temp
> in winter so I hope to cash in on some of
> the inevitable heat loss from house into
> this space. Warmer in summer of course.
> Would be fun to think of a way of 'preheating'
> the mains water going to the HW supply up here as well.
> A degree or two would make all the difference would it not?
Just have an adequate combi or heat bank.
> I sometimes wonder if the bath/shower
> waste couldn't be made to warm
> up the incoming cold water on it's way to the street.
Gfx a thread is already on this:
<http://gfxtechnology.com/>
Try just having a cylinder as a CH buffer heated by a combi via a fast
recovery coil, or a plate heat exchanger and pump. The plate & pump and
direct cylinder may work out cheaper than a fast recovery coil, and it
operates far better too.
Have a combi suited to your DHW needs and fit an accumulator tank. Then no
open tanks in the loft, except one F&E tank supplying the CH buffer
cylinder. Look at:
Replaceable Membrane Potable at:
<http://www.rwc.co.uk/Product.aspx?page=CAT6>
If you need 100 litres of cold water storage, then get a 200 litres model.
The membranes are replaceable. Pump up with car pump.
Doctor Drivel
<i...@5roses.co.uk> wrote in message
news:06bc4f82-e99b-46f3...@k39g2000hsf.googlegroups.com...
37L is quite good. If one 15mm pipe and all cold appliances teed off inc
combi then a no. no. If you have to go back to the stoptap, do it in 22mm
only for the combi.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> frank...@hotmail.co.uk wrote:
> If have a vented primary circuit then you could heat it directly or
> indirectly. Personally I favour a sealed primary, and hence would opt for
> indirect heating of the store.
Please stop guessing. Best have direct all the way and elimate heat
exchangers and improve efficiency.
> Or cut the complexity, go for a boiler with a decent modulation range, and
> let the boiler drive the rads directly.
Which is an expensive more complex boiler and non modulate down low enough
and an auto by-pas has to be used reducing efficiency on part load. You need
to understand buffering. Big in Germany. Fitting one combi does not make
you a heating engineer.
> (dribble prefers his one size fits all solution using the store for
> everything, as you can probably judge from the previous messages)
....an amateur heating man speaks
> If you really want lots of zones you may be better with a pair of largish
> primary "backbone" pipes providing flow and return points for each floor,
> and then teeing off them for the individual rooms / zones.
Pumps under the floors? Shishhhhh. Best have all controls in one place.
This pipe will just return back to the boiler raising the return temp
lowering efficiency.
> You may find a combi with its HW output feeding the shower, and a fast
> recovery indirect cylinder on a zone on the heating side of the boiler
> would meet that requirement better.
Er no..... Best have a cold water accumuator.
John Rumm
> Just got round to measuring flow rate and opening all cold taps at
> once and measuring total quantity of water in 1 minute, it looks like
> I have a flow rate of about 37L/min. Hopefully, that is pretty good.
Yup, that is very good.
> As to pressure, don't have a guage for this but believe it to be very
> strong. can't hold thumb over tap without water still spurting out
> quite forcefully. (Very scientific I know but seem to remember someone
> suggesting that once!)
It does not take much static pressure to defeat the thumb over the end
gambit ;-) 1.5 bar would do it.
> Also checked existing pipework and as I currently have a combi,
> pipework to bath is in 15mm. Is it necessary to upgrade it 22mm? Would
> be bit of a pain if need to as bathroom all tiled etc. Would mean a
> long route of going downstairs then back up again.
At mains pressure that will probably be fine.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> i...@5roses.co.uk wrote:
>
>> Just got round to measuring flow rate and opening all cold taps at
>> once and measuring total quantity of water in 1 minute, it looks like
>> I have a flow rate of about 37L/min. Hopefully, that is pretty good.
>
> Yup, that is very good.
>
>> As to pressure, don't have a guage for this but believe it to be very
>> strong. can't hold thumb over tap without water still spurting out
>> quite forcefully. (Very scientific I know but seem to remember someone
>> suggesting that once!)
>
> It does not take much static pressure to defeat the thumb over the end
> gambit ;-) 1.5 bar would do it.
>
>> Also checked existing pipework and as I currently have a combi,
>> pipework to bath is in 15mm. Is it necessary to upgrade it 22mm? Would
>> be bit of a pain if need to as bathroom all tiled etc. Would mean a
>> long route of going downstairs then back up again.
>
> At mains pressure that will probably be fine.
Until another taps is turned on.
John Rumm
> "John Rumm" <see.my.s...@nowhere.null> wrote in message
> news:13okro2...@corp.supernews.com...
>> frank...@hotmail.co.uk wrote:
>
>> If have a vented primary circuit then you could heat it directly or
>> indirectly. Personally I favour a sealed primary, and hence would opt
>> for indirect heating of the store.
>
> Please stop guessing. Best have direct all the way and elimate heat
> exchangers and improve efficiency.
As you have said yourself on many occasions, the efficiency of a plate
heat exchange is very good. Sealed systems are generally preferable when
they can be used.
>> Or cut the complexity, go for a boiler with a decent modulation range,
>> and let the boiler drive the rads directly.
>
> Which is an expensive more complex boiler and non modulate down low
More hand waving dribble? How much more complex?
Answer - very little difference. Different gas valve perhaps, but these
rarely fail anyway. Still has much the same burner layout, electronic
controls, ignition, forced induction, condensate collection and disposal
etc. Price difference? hundred perhaps. Hardly figures in the grand
scheme of things does it?
> enough and an auto by-pas has to be used reducing efficiency on part
> load. You need to understand buffering. Big in Germany. Fitting one
> combi does not make you a heating engineer.
Posting ill thought through "solutions" on usenet does not make you one
either. Neither does you inability to maintain any grip on capital cost
of your projects.
>> If you really want lots of zones you may be better with a pair of
>> largish primary "backbone" pipes providing flow and return points for
>> each floor, and then teeing off them for the individual rooms / zones.
>
> Pumps under the floors? Shishhhhh.
Who suggested under the floor? You it seems. You are right though, daft
idea.
> Best have all controls in one place.
With a boatload of pipe running to and from each zone...
> This pipe will just return back to the boiler raising the return temp
> lowering efficiency.
Which pipe?
I think you will find flow and return pipes with rads strung across them
is pretty much how most heating systems work (if you ignore old single
pipe systems). Perhaps you should read up on the background a little.
>> You may find a combi with its HW output feeding the shower, and a fast
>> recovery indirect cylinder on a zone on the heating side of the boiler
>> would meet that requirement better.
>
> Er no..... Best have a cold water accumuator.
Ah right, and how much does that cost?
20 lpm while not a huge supply rate is not dire, and more than adequate
for a shower.
Note also if you go back to the OPs requirements: "I'm renewing the
boiler and propose to use a combi as a replacement. For HW I'm happy
with the flow rate this will give. We use modest amounts of hot water
don't need a big store in reserve."
Its funny how you flipflop between "a combi is ideal because there is no
room for tanks in small British houses", to "Oh just slap in a 300L
accumulator alongside the heatbank" depending on which way it suits your
argument.
(not suggesting an accumulator is a bad idea in general - it has a place
in some installations. Just entertained how your solutions run on and on
sucking in ever more hardware to get yourself out of corners you have
designed yourself into, with no concept of capital cost)
Doctor Drivel
> Doctor Drivel wrote:
>
>> "John Rumm" <see.my.s...@nowhere.null> wrote in message
>> news:13okro2...@corp.supernews.com...
>>> frank...@hotmail.co.uk wrote:
>>
>>> If have a vented primary circuit then you could heat it directly or
>>> indirectly. Personally I favour a sealed primary, and hence would opt
>>> for indirect heating of the store.
>>
>> Please stop guessing. Best have direct all the way and elimate heat
>> exchangers and improve efficiency.
>
> As you have said yourself on many occasions, the efficiency of a plate
> heat exchange is very good.
But not better than direct which eliminated them completely.
> Sealed systems are generally preferable when they can be used.
Are they? New on me. Since when?
>>> Or cut the complexity, go for a boiler with a decent modulation range,
>>> and let the boiler drive the rads directly.
>>
>> Which is an expensive more complex boiler and does not modulate down low
>> enough.
>
> More hand waving dribble? How much more complex?
A lot. Look at a Glow Worm HXi inside. Not much there at all.
> Answer - very little difference.
Says the amateur.
> Price difference? hundred perhaps. Hardly figures in the grand scheme of
> things does it?
A top quality boiler that modulates low, none go low enough, with decent
control is north of £1K more like £1.5k
>> enough and an auto by-pas has to be used reducing efficiency on part
>> load. You need to understand buffering. Big in Germany. Fitting one
>> combi does not make you a heating engineer.
>
> Posting ill thought through "solutions" on usenet does not make you one
> either.
I am one. That is obvious as you learnt a lot from me :-)
> Neither does you inability to maintain any grip on capital cost of your
> projects.
How many projects have you undertaken? Mmmm...none!! Apart form fitting
your own combi.
>>> If you really want lots of zones you may be better with a pair of
>>> largish primary "backbone" pipes providing flow and return points for
>>> each floor, and then teeing off them for the individual rooms / zones.
>>
>> Pumps under the floors? Shishhhhh.
>
> Who suggested under the floor? You it seems. You are right though, daft
> idea.
Local control from loop pipe means local equipment in odd places, usually
under the floor.
> > Best have all controls in one place.
>
> With a boatload of pipe running to and from each zone...
....and ease of fitting, maintenace and setting up. The pipe to rads can be
microbore. The heat bank/buffer is in a central location. The OP stated
that.
>> This pipe will just return back to the boiler raising the return temp
>> lowering efficiency.
>
> Which pipe?
This loop you are on about. What other pipe were you on about?
> I think you will find flow and return pipes with rads strung across them
> is pretty much how most heating systems work (if you ignore old single
> pipe systems). Perhaps you should read up on the background a little.
You were advocating a loop, which is a glorified header around the house
giving off heat where not needed.
>>> You may find a combi with its HW output feeding the shower, and a fast
>>> recovery indirect cylinder on a zone on the heating side of the boiler
>>> would meet that requirement better.
>>
>> Er no..... Best have a cold water accumuator.
>
> Ah right, and how much does that cost?
£300 to £400. A Stuart Turner pump for one shower is around £250, more for
higher pressures, then the fittings on top...and the noise too. This does
"all" of the house and stores cold water too. I have put a number in to
great success. Very impressive. They work well with heat banks and high
flow combis.
> 20 lpm while not a huge supply rate is not dire, and more than adequate
> for a shower.
>
> Note also if you go back to the OPs requirements: "I'm renewing the boiler
> and propose to use a combi as a replacement. For HW I'm happy with the
> flow rate this will give. We use modest amounts of hot water don't need a
> big store in reserve."
>
> Its funny how you flipflop between "a combi is ideal because there is no
> room for tanks in small British houses", to "Oh just slap in a 300L
> accumulator alongside the heatbank" depending on which way it suits your
> argument.
His house is big. He explained that. The accumulator can go in a garage,
loft, garage loft (where I have put them) or just about anywhere. He has
the choice of open cold tanks or an accumulator which will give superb mains
cold water flow and pressure, eliminating pumps
If he had no space then a high flow combi and a new mains pipe to the street
is the way.
> (not suggesting an accumulator is a bad idea in general - it has a place
> in some installations. Just entertained how your solutions run on and on
> sucking in ever more hardware to get yourse
They change to what the OP responds as he releases more info. I can't mind
read. If I was him I would make up a DHW/CH buffer heat bank and fit an
accumulator. First I would see what the cost and difficulties are to get
the mains pipe upgraded. Even if it costs £500 then I would have a new
mains pipe and drop the accumulator. The accumulator is a get out of jail
solution to poor mains pressure problems, although a brilliant one. It
stores cold water, gives it at high flow and pressure eliminating pumps,
enables the use of mixer taps all around with aerated heads to use less
water, no pump noise, electricity used, etc.
frank...@hotmail.co.uk
Just to say thanks again for all the input.
I have been through the whole thread now and found DD's description of
how to
convert a cylinder from August 2007.
Also a couple of useful schematics.
Just getting my head round the responses overnight and today.
I'll try to come back with some thought out final system options that
suit my pocket/ability/temperament and some sensible points for
clarification later on.
I think this house is pretty leaky/poor u values. there is more to do
in the draught exclusion dept. The IDHEE calculator said I needed a
28kw boiler. It is a mid row terrace with partial DG and good loft/
basement insulation but stone with plaster and lathe dry lining
against quite a few external walls. Certainly some rooms cool down
pretty fast.
Is there a good heat loss calculator for rooms I could use? It has
been mentioned several times. How should I apply the info?
More later.
Thanks again.
Frank Front
frank...@hotmail.co.uk
If 25lpm @ 2.0bar 25lpm @ 1.5bar might be a problem as you seem to
suggest (measured at top of house) would it help to replace the 15mm
from the stop cock at ground level with 22mm pipe?
I think the lead inside diameter is more than 15mm but less than
22mm. It's about 7m of vertical pipe to get to the boiler if I put it
on the top floor as I propose. (Rooms about 3.5m high on ground and
first floors).
(Doing my best to give you all the relevant info without writing a
book.)
Frank
John Rumm
> I think this house is pretty leaky/poor u values. there is more to do
That was the point I was making to dribble about modulating boilers. The
fact that the boiler can't modulate from 0kW to full output is
generally neither here nor there since the house will still have some
heat losses. Even a reasonably well insulated place is going to leak a
few kW - so a boiler that modulated from say 6kW will be able to run
giving a nett contribution of only a couple of kW upwards. This will
allow efficient running with relatively little cycling even without the
thermal store.
One thing a store does very well, is allow very high flow rates of hot
water at mains pressure - but this is something you have said you are
not that fussed about. They were also very good in the days when boilers
only ran at high fixed outputs - acting as a buffer allowing the boiler
to do longish burns heating the store, while in turn it fed heat to the
house at a slower rate. While this is still the case, a modulating
boiler can make a pretty good stab at doing this all by itself these
days. So, IMO, the advantages are far less significant. The 90%+ SEDBUK
ratings on modern boilers assume typical setups and controls, so even if
you can improve on the efficiency and squeeze few % more out of the
system, you need to assess if the extra hardware and install costs of
the store are going to give worthwhile returns. There is a fair chance
that in financial terms alone they never will unless you have huge gas
bills. So will you get improvements in comfort or functionality to make
the cost worthwhile?
> in the draught exclusion dept. The IDHEE calculator said I needed a
> 28kw boiler. It is a mid row terrace with partial DG and good loft/
If you genuinely are leaking 20+ kW then you need to spend money on
insulation and draft proofing as a matter of urgency! Having said that
many of these heat loss calculators tend to overestimate. You can
probably get a much better feel for the actual numbers if you just do it
with a spreadsheet.
(I have an example sheet if you want a copy - but see the end of this
email for a worked example).
I found on my place (5 bed semi, three storey, 9" solid wall + render,
dg all round, and top storey insulated to modern standards) that worst
cases losses (i.e. -3 degrees C outside) were about 8.6kW. With the
outside temp at a more typical 10 degrees, that falls to 3.5kW.
> basement insulation but stone with plaster and lathe dry lining
> against quite a few external walls. Certainly some rooms cool down
> pretty fast.
>
> Is there a good heat loss calculator for rooms I could use? It has
> been mentioned several times. How should I apply the info?
There is a Myson one that is not bad - used to be available on their web
site but IIRC is not currently. Andy Hall may be able to lob you a copy
if you email him. Failing that, a spreadsheet, some u-values, surface
areas, and air change estimates will mean you can DIY.
Heat loss for a room:
you need to compute the area (in m^2) of each of the main surfaces. You
need to know the target temperature for your rooms, make a gustimate at
the likely air changes per hour, and know something of the construction
of the walls etc.
[fixed width font will help here]
Typical room parameters
Room type Room temp Air Changes
Lounge 21 1
Dining Room 21 2
Bedroom 18 0.5
Hall and Landing16 1.5
Bathroom 22 2
Kitchen 18 2
Material parameters:
Materials u-Value
Wall - outer 9" solid brick 2.2
Wall - internal plaster over 4" block 1.2
Wall - internal PB over stud 1.8
Floor (ground) - solid concrete 0.8
Floor - PB + joist + FB flow up 1.9
Floor - PB + joist + FB flow down 1.5
Roof pitched with felt + 100* insulation 0.3
Window - wood DG 2.9
Window - wood - low E 1.7
Door single glaze 3
Wall Insulated 0.6
* insulation assumed to be high performance foiled PIR foam
Example room:
Room Surface Area Tdelta u-value Loss AirC Vol
Lounge Front Wall 4.40 24 2.2 232 1.00 31
Window 4.80 24 2.9 334
Party Wall 8.40 0 2.2 0
Hall Wall 8.40 5 1.2 50
Rear Wall 6.90 0 1.2 0
Floor 13.45 24 1.9 613
Ceiling 13.45 3 1.9 77
Total 1307 267 1574
So in this example you can see there is 4.4m^2 of outside wall (and
4.8m^2 of window). The temperature difference is 24 degrees (assuming -3
outside). That means you lose 232W (area x TDelta x u-value) through the
wall, and 334W through the window. If you look at another wall - say the
party wall, the nett loss is zero since I am assuming next door's lounge
will be at least as hot as ours. Add all the losses (some of which may
be negative - i.e gains from an adjacent rooms) and you get 1.3kW. Next
deal with the air changes.
You compute room volume (31m^3 in this case, the floor area x the room
height). That is 0.36 x TDelta x Num air changes per hour x volume. (the
0.36 being constant based on the heat capacity of the air). This figure
will be a bit pessimistic since it assumes all the air changes are
happening with your nice heated air and cold outside air.
Add the two together and you get a total for this room of a tad under
1.6kW. That lets you size the rad for the room, as well as being part of
the answer for the house as a whole.
frank...@hotmail.co.uk
I think losses can't be as bad as the calculation I gave you and I've
a feeling that included hot water needs. If that makes a difference.
The radiators in the rooms aren't huge and they do okay without the
existing very ancient Potterton kingfisher ll being cranked up to more
than just over half on the temperature knob. It seems to be about
28Kw.
In the rooms where the chimney losses are controlled and the shutters
get closed things are fine. However when the rads go off on a
particularly cold evening it becomes apparent pretty quickly.
On a slightly different tack I would be very interested in what the
inefficiencies/short-comings you and DD reckon would result from the
following (as it would help me to compare better with the outcome of
the heat bank method).
So considering CH only now:
Using a boiler for the CH complete the usual frills - weather sensor,
modulation, user adjustable bypass valve. What exactly are the
efficiency short-comings going to be if I zone that output (I've
manged to crunch down from ten zones to seven) using simple room stats
linked to centrally placed timers and conveniently located valves?
It would be very easy in my set up to pop a simple thermostat into
every zone with out any making good necessary.
In the bumf for most boilers it seems to assume one is going to just
fit TRV's to all the radiators and have a thermostat in the kitchen by
way of interlock block. This would be wasteful and inconvenient for
the way we use our house. (Though I do take your point about a cool
room sinking heat from a warm one.)
With the set-up I've outlined above I am not sure how to create the
interlock block. A 'master' stat might spoil it for some other part
of the house if it switches off. I imagine a secondary circuit
linking all the room stats in parallel would be needed so that when
none of them are calling for water the boiler stops. Is that right?
Incidentally taking our lounge for an example the floor area is about
26msq with one external wall with a DG bay window. The radiators
(against the external wall) I inherited are a total of about 1.6kw and
are fine if the shutters are closed and it isn't really bitter out.
To my shame I have to report that a) a sofa is pressed hard up against
the largest one, b) the chimney is partially open.
Thanks again to you and DD for your time and insights. I look forward
to your responses to the above.
Frank.
John Rumm
> I think losses can't be as bad as the calculation I gave you and I've
> a feeling that included hot water needs. If that makes a difference.
They probably do... whether you need to depends on the type of water
system you have and your usage:
Traditionally they would add on say 5kW for HW and assume use of a mid
position valve that would allow the HW to be heated at the same time as
the rads. The cylinder coil would have been limited to approx 5kW
transfer anyway (which would give slow recovery times), so it made sense
to add the HW load to the heating one and run them together.
With a storage system that has fast recovery, it may well be able to
take all (or a sizeable part) of the boilers output, hence the
configuration that assigns priority to the water heating. Get the HW
reheated quick and then switch back to the CH after.
With a combi, then you can ignore the CH side altogether in most cases
and just size it for the HW requirements. Again it assigns priority to
the HW in that it can only heat one at a time.
> The radiators in the rooms aren't huge and they do okay without the
> existing very ancient Potterton kingfisher ll being cranked up to more
> than just over half on the temperature knob. It seems to be about
> 28Kw.
If you have any marginally sized rads, then now would be a good time to
change them. Allowing for use of lower flow temps is also a good idea.
In many cases swapping single panel to double or ones without fins to
finned ones can let you do this with relatively little upheaval.
> In the rooms where the chimney losses are controlled and the shutters
> get closed things are fine. However when the rads go off on a
> particularly cold evening it becomes apparent pretty quickly.
Which sounds like you have quite high rates of air change in these
rooms. Sometimes just fixing drafts from windows etc can make a
difference even if you leave a chimney open since it prevents a through
draft.
> On a slightly different tack I would be very interested in what the
> inefficiencies/short-comings you and DD reckon would result from the
> following (as it would help me to compare better with the outcome of
> the heat bank method).
>
> So considering CH only now:
>
> Using a boiler for the CH complete the usual frills - weather sensor,
> modulation, user adjustable bypass valve. What exactly are the
> efficiency short-comings going to be if I zone that output (I've
> manged to crunch down from ten zones to seven) using simple room stats
> linked to centrally placed timers and conveniently located valves?
I would be surprised if you could not loose a few more zones by lumping
together some rooms that have roughly similar usage even if not identical.
You may want to consider using a prog stat in place of a conventional
one and timer. Not only do they tend to be more accurate stats than the
bog standard mechanical ones, they allow much better control of
temperature to suit your usage.
> It would be very easy in my set up to pop a simple thermostat into
> every zone with out any making good necessary.
Yup, if you choose the room in the zone to be the one that is hardest to
heat, and stick TMVs on the other rads in the zone.
> In the bumf for most boilers it seems to assume one is going to just
> fit TRV's to all the radiators and have a thermostat in the kitchen by
> way of interlock block. This would be wasteful and inconvenient for
> the way we use our house. (Though I do take your point about a cool
> room sinking heat from a warm one.)
Well you can do similar - but with a stat per zone etc.
> With the set-up I've outlined above I am not sure how to create the
> interlock block. A 'master' stat might spoil it for some other part
If you have a stat for every zone then that achieves the goal. Once the
house is to temperature, there will be no call for heat from any of the
stats.
> of the house if it switches off. I imagine a secondary circuit
> linking all the room stats in parallel would be needed so that when
> none of them are calling for water the boiler stops. Is that right?
They can in effect be wired in parallel to generate a call for heat.
When they are all satisfied there will be no call. (you may choose to
implement this using the switches on the zone valves rather than the
signal directly from the stat. A neon can also then wired up for each
valve to give you a handy "valve failed" indication by lighting up when
volts are applied to one side of its switch from the stat, but the
switch remains open)
frank...@hotmail.co.uk
some more from Dr Drivel soon.
In the mean time I take your point about prog stats however my
thinking was to keep the cost of zoning down by using basic analogue
stats which are cheap and have bimetallic strips so (I imagine) have a
wider hysteresis that digital so would reduce activity at the valves.
If I used centrally placed timers for the zones - as DD pointed out
less running around - they could be basic two channel timers normally
used for CH and HW but on this occasion two zones. The CH channel
will likely have a 'boost' facility which could be given to the most
deserving of the two zones controlled. This is the cheapest way of
zoning I could think of.
As you say TRVs on the secondary radiators on any given zone.
I like the idea of the neons for the valves. Nothing like a steady
red light for comfort.
Hope to hear more from Dr Drivel soon as you both seen to have
different and very informative views on the same things.
More thought required by me on the best overall approach and
specifically which way to jump on the HW provision - combi or HB...
Regards,
Frank.
John Rumm
> John thanks for that. All grist to the mill. I'm hoping we'll hear
> some more from Dr Drivel soon.
Not often you read that in this group ;-)
> In the mean time I take your point about prog stats however my
> thinking was to keep the cost of zoning down by using basic analogue
Horstman prog stats are only about £24 in screwfix.
> stats which are cheap and have bimetallic strips so (I imagine) have a
> wider hysteresis that digital so would reduce activity at the valves.
at the expense of bigger swings in temperature - the prog ones do make a
noticeable difference to comfort.
> If I used centrally placed timers for the zones - as DD pointed out
> less running around - they could be basic two channel timers normally
> used for CH and HW but on this occasion two zones. The CH channel
> will likely have a 'boost' facility which could be given to the most
> deserving of the two zones controlled. This is the cheapest way of
> zoning I could think of.
It looses the ability to have the temperature of the zone vary over the
day though - this is one of the big wins with a prog stat. In a bedroom
for example to have it warmer as you wake and go to bed, but then
setback overnight and during the day etc.
> As you say TRVs on the secondary radiators on any given zone.
>
> I like the idea of the neons for the valves. Nothing like a steady
> red light for comfort.
Would be easiest to wire so that they only come on when a valve has a
demand, that has not been satisfied... but yes in general a cheap LED or
neon can make a massive difference to the ability to diagnose problems
quickly.
> Hope to hear more from Dr Drivel soon as you both seen to have
> different and very informative views on the same things.
Dribble seems to make it a matter of principle to adopt a contrary view
on everything. ;-)
> More thought required by me on the best overall approach and
> specifically which way to jump on the HW provision - combi or HB...
The choice is yours... ;-)
Doctor Drivel
>> On a slightly different tack I would be very interested in what the
>> inefficiencies/short-comings you and DD reckon would result from the
>> following (as it would help me to compare better with the outcome of
>> the heat bank method).
>>
>> So considering CH only now:
>>
>> Using a boiler for the CH complete the usual frills - weather sensor,
>> modulation, user adjustable bypass valve. What exactly are the
>> efficiency short-comings going to be if I zone that output (I've
>> manged to crunch down from ten zones to seven) using simple room stats
>> linked to centrally placed timers and conveniently located valves?
Efficiency shortgains are that by-pass opens on part load to create a direct
shortcut to the boiler raising the return temp far too high. That is if it
is set properly, which most are not, and even then they can run out of
setting in time. They can also restrict flow through the boiler too,
causing heat exchanger damage. When heating a thermal store cylinder
directly there is always full flow through the boiler. The boiler is
operating in an ideal hydraulic environment, which means it will last longer
and be more efficient.
> You may want to consider using a prog stat in place of a conventional one
> and timer. Not only do they tend to be more accurate stats than the bog
> standard mechanical ones, they allow much better control of temperature to
> suit your usage.
But no central control.
>> It would be very easy in my set up to pop a simple thermostat into
>> every zone with out any making good necessary.
>
> Yup, if you choose the room in the zone to be the one that is hardest to
> heat, and stick TMVs on the other rads in the zone.
Best have TRVs all around and no stat to cut out when some rooms require
heat.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> frank...@hotmail.co.uk wrote:
>
>> I think this house is pretty leaky/poor
>> u values. there is more to do
>
> That was the point I was making to dribble about modulating boilers. The
> fact that the boiler can't modulate from 0kW to full output is generally
> neither here nor there since the house will still have some heat losses.
Oh my God, Chav, you really haven't a clue. Most boiler don't go below 8Kw
when up to temp the house will be calling for less than 8kW and then
inefficient boiler cycling occurs with the by-pass valve opening and then
efficiency drops like a stone.
A heat bank/thermals store can trickle kWs into a heating system and no
impair boiler performance, efficiency and longevity either.
> One thing a store does very well, is allow very high flow rates of hot
> water at mains pressure
Cha, you are getting it.
> They were also very good in the days when boilers only ran at high fixed
> outputs
They are still very, very good, nothing has changed.
> - acting as a buffer allowing the boiler to do longish burns heating the
> store, while in turn it fed heat to the house at a slower rate. While
> this is still the case, a modulating boiler can make a pretty good stab at
> doing this all by itself these days.
A poor stab at it I'm afraid. Modern boilers are designed for the
replacement boioer market, where rads were designed to run at 82C, hence
modulation which is not that effective a sthe boiler makers tells us. Then
TRVs on all rads makes matters worse for the boioetr. When having TRVs all
around best have them fed froma buffer cylinder (thermal store)
> The 90%+ SEDBUK ratings on modern boilers assume typical setups and
> controls, so even if you can improve on the efficiency and squeeze few %
> more out of the system, you need to assess if the extra hardware and
> install costs of the store are going to give worthwhile returns.
A boiler can be running at over 100% if set up properly heating a store.
> There is a fair chance that in financial terms alone they never will
> unless you have huge gas bills.
Chav, you just made that up.
> So will you get improvements in comfort or functionality to make the cost
> worthwhile?
Most certainly!
Heat Loss:
If a boiler is correctly sized for the heat loss at say -3C outside, when -3
it should run flat out continuously. Few do as most are oversized, then
boiler cycling occurs.
A great thing about a thermal store is that doesn't care how large the
boiler is, as long as the flow and return pipes are sized correctly. If a
house requires say 15kW and a 30kW boiler is coupled to the store cylinder,
it will just heat up faster and still no cycling. A boiler twice the size
of CH requirements directly heating rads will cycle like hell.
Also having the CH and DHW off a thermal store 100% electric backup is
available to CH & DHW, and also a second cheap backup boiler can be coupled
directly to the store too. So, a cheapie B&Q job boiler can act as a backup.
It will last as it will only be used once in a blue moon - so full cheap to
run on gas, 100% backup. Or have both boilers on and zippo re-heat. Great
when there is multiple showers and baths going on.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> frank...@hotmail.co.uk wrote:
>
>> John thanks for that. All grist to the mill. I'm hoping we'll hear
>> some more from Dr Drivel soon.
>
> Not often you read that in this group ;-)
You tend to get this:
http://tinyurl.com/2wdd25
>>>>>>
> The Elson Coral ST thermal store. All Elson "Coral" products are square
> thermal stores that can be easily packaged in high positions or under
> worktops. They have about 3 variations. They may be able to make one to
> your specific size, call them.
You absolute God. The Coral Si is perfect,
though they may even be able to
do better, because for a small cost.
<<<<<<<
>> If I used centrally placed timers for the zones - as DD pointed out
>> less running around - they could be basic two channel timers normally
>> used for CH and HW but on this occasion two zones. The CH channel
>> will likely have a 'boost' facility which could be given to the most
>> deserving of the two zones controlled. This is the cheapest way of
>> zoning I could think of.
>
> It looses the ability to have the temperature of the zone vary over the
> day though - this is one of the big wins with a prog stat. In a bedroom
> for example to have it warmer as you wake and go to bed, but then setback
> overnight and during the day etc.
He could just have the timer switch on the bedrooms evening and morning.
Simple.
>> Hope to hear more from Dr Drivel soon as you both seen to have
>> different and very informative views on the same things.
>
> Dribble seems to make it a matter of principle to adopt a contrary view on
> everything. ;-)
Chav, I am a pro not an amateur. I look at thing logically, not what I have
fitted in my own house - which in your case is one combi.
John Rumm
>> Dribble seems to make it a matter of principle to adopt a contrary
>> view on everything. ;-)
>
> Chav, I am a pro not an amateur. I look at thing logically, not what I
> have fitted in my own house - which in your case is one combi.
let me guess, I should have fitted two?
(odd we have not had the pet solution for ages now, are you fed up with
it?, it used to get an outing several times a week)
John Rumm
>> - acting as a buffer allowing the boiler to do longish burns heating
>> the store, while in turn it fed heat to the house at a slower rate.
>> While this is still the case, a modulating boiler can make a pretty
>> good stab at doing this all by itself these days.
>
> A poor stab at it I'm afraid. Modern boilers are designed for the
And yet still exceed 90% SEDBUK rating... how much more will your store get?
>> The 90%+ SEDBUK ratings on modern boilers assume typical setups and
>> controls, so even if you can improve on the efficiency and squeeze few
>> % more out of the system, you need to assess if the extra hardware and
>> install costs of the store are going to give worthwhile returns.
>
> A boiler can be running at over 100% if set up properly heating a store.
Oh free energy, interesting concept...
>> There is a fair chance that in financial terms alone they never will
>> unless you have huge gas bills.
>
> Chav, you just made that up.
No, actually I did the sums. It an engineering activity you ought to try
once in a while. It can save you spending 1000's trimming £10 off you
gas bill.
>> So will you get improvements in comfort or functionality to make the
>> cost worthwhile?
>
> Most certainly!
>
> Heat Loss:
>
> If a boiler is correctly sized for the heat loss at say -3C outside,
> when -3 it should run flat out continuously. Few do as most are
> oversized, then boiler cycling occurs.
>
> A great thing about a thermal store is that doesn't care how large the
> boiler is, as long as the flow and return pipes are sized correctly. If
> a house requires say 15kW and a 30kW boiler is coupled to the store
> cylinder, it will just heat up faster and still no cycling. A boiler
> twice the size of CH requirements directly heating rads will cycle like
> hell.
unless it modulates down to match the load... oh hang on a minute most
of them do.
> Also having the CH and DHW off a thermal store 100% electric backup is
> available to CH & DHW, and also a second cheap backup boiler can be
> coupled directly to the store too. So, a cheapie B&Q job boiler can act
> as a backup. It will last as it will only be used once in a blue moon -
> so full cheap to run on gas, 100% backup. Or have both boilers on and
> zippo re-heat. Great when there is multiple showers and baths going on.
Wahay! Two combis almost makes an appearance...
So let me get this straight, so far the shopping list for the system is:
two boilers, one accumulator, a thermal store, half a dozen time dual
channel time switches, about 15 pumps, half a mile of copper pipe, a
couple of blending valves, weather compensator, immersion heater... (did
I forget anything - been losing track)
spose you might get change from £4k and a MTBF comparable to you collar
size.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> Doctor Drivel wrote:
>
>>> Dribble seems to make it a matter of principle to adopt a contrary view
>>> on everything. ;-)
>>
>> Chav, I am a pro not an amateur. I look at thing logically, not what I
>> have fitted in my own house - which in your case is one combi.
>
You are getting there.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> Doctor Drivel wrote:
>
>>> - acting as a buffer allowing the boiler to do longish burns heating the
>>> store, while in turn it fed heat to the house at a slower rate. While
>>> this is still the case, a modulating boiler can make a pretty good stab
>>> at doing this all by itself these days.
>>
>> A poor stab at it I'm afraid. Modern boilers are designed for the
>
> And yet still exceed 90% SEDBUK rating.
In a setup where the boiler set properly. Not the case in most systems.
Then the auto by-pass runs out of setting.
>> A boiler can be running at over 100% if set up properly heating a store.
>
> Oh free energy, interesting concept...
You really don't know.
>> If a boiler is correctly sized for the heat loss at say -3C outside,
>> when -3 it should run flat out continuously. Few do as most are
>> oversized, then boiler cycling occurs.
>>
>> A great thing about a thermal store is that doesn't care how large the
>> boiler is, as long as the flow and return pipes are sized correctly. If
>> a house requires say 15kW and a 30kW boiler is coupled to the store
>> cylinder, it will just heat up faster and still no cycling. A boiler
>> twice the size of CH requirements directly heating rads will cycle like
>> hell.
>
> unless it modulates down to match the load...
None of them modulate low enough.
>> Also having the CH and DHW off a thermal store 100% electric backup is
>> available to CH & DHW, and also a second cheap backup boiler can be
>> coupled directly to the store too. So, a cheapie B&Q job boiler can act
>> as a backup. It will last as it will only be used once in a blue moon -
>> so full cheap to run on gas, 100% backup. Or have both boilers on and
>> zippo re-heat. Great when there is multiple showers and baths going on.
>
> Wahay! Two combis almost makes an appearance...
You should fit two combis.
> So let me get this straight, so far the shopping list for the system is:
>
> two boilers, one accumulator, a thermal store, half a dozen time dual
> channel time switches, about 15 pumps, half a mile of copper pipe, a
> couple of blending valves, weather compensator, immersion heater... (did I
> forget anything - been losing track)
That would be a good system indeed. Cost effective for the functionality.
John Rumm
>
> "John Rumm" <see.my.s...@nowhere.null> wrote in message
> news:13oqud8...@corp.supernews.com...
>> Doctor Drivel wrote:
>>
>>>> - acting as a buffer allowing the boiler to do longish burns heating
>>>> the store, while in turn it fed heat to the house at a slower rate.
>>>> While this is still the case, a modulating boiler can make a pretty
>>>> good stab at doing this all by itself these days.
>>>
>>> A poor stab at it I'm afraid. Modern boilers are designed for the
>>
>> And yet still exceed 90% SEDBUK rating.
>
> In a setup where the boiler set properly. Not the case in most systems.
> Then the auto by-pass runs out of setting.
Perhaps you could translate: "Then the auto by-pass runs out of
setting." into English.
>>> A boiler can be running at over 100% if set up properly heating a store.
>>
>> Oh free energy, interesting concept...
>
> You really don't know.
I know you won't see a SEDBUK rating of over 100% since they are using
the gross calorific value in their calculations. So here in the real
world, with normal physics and all that, 100% is the maximum you can
possibly get - when all the energy from the fuel you put in, is captured
and put to good use.
>>> If a boiler is correctly sized for the heat loss at say -3C outside,
>>> when -3 it should run flat out continuously. Few do as most are
>>> oversized, then boiler cycling occurs.
>>>
>>> A great thing about a thermal store is that doesn't care how large
>>> the boiler is, as long as the flow and return pipes are sized
>>> correctly. If a house requires say 15kW and a 30kW boiler is coupled
>>> to the store cylinder, it will just heat up faster and still no
>>> cycling. A boiler twice the size of CH requirements directly heating
>>> rads will cycle like hell.
>>
>> unless it modulates down to match the load...
>
> None of them modulate low enough.
Think through the implications.
Say you have a boiler that modulates down to 6kW, and lets guess that
the OPs three storey stone built house loses heat at a rate of 4kW on a
moderate day. Now aside from the fact the boiler will probably be
running at its highest efficiency at this output, you will also note
that the nett contribution of power to the building is 2kW.
Now if you have ever used a nett input of 2kW from a fan heater to try
and heat any space of significant size (like an entire house for
example), you will realise that in real terms this is a very low rate of
heat input - and you will get very little cycling of the boiler on its
internal stat. What little you do get will have little effect on overall
seasonal efficiency.
>> So let me get this straight, so far the shopping list for the system is:
>>
>> two boilers, one accumulator, a thermal store, half a dozen time dual
>> channel time switches, about 15 pumps, half a mile of copper pipe, a
>> couple of blending valves, weather compensator, immersion heater...
>> (did I forget anything - been losing track)
>
> That would be a good system indeed. Cost effective for the functionality.
Well lets say it squeezed an extra 5% out of the boiler (which seems
unlikely - a SEDBUK efficiency around 90% usually corresponds to a
boiler efficiency of some 92% or more, so we would have to be pushing
97% recovery at the boiler to achieve that).
Your above "cost effective" system has added £2k - 3k to the install
cost. Lets say the gas usage for heating is pretty high at £500/year,
that extra saving could be as much as £25. So you could see a return on
your investment in as little as 80 years. (assuming you don't pay that
saving over for extra electricity to run all those pumps)
frank...@hotmail.co.uk
Thanks for all the further input.
I think I know now how I want to manage the zones either with an HB or
a combi.
However, I suspect that the actual saving either way (HB or combi) are
fairly minimal. It's more a question of initial outlay, system
flexibility, ease of servicing and future proofing (ie electric
immersion back up or solar energy when the Russians cut off the gas).
Many of the boxes are ticked by a heat bank - perhaps a few more than
the combi. There is a greater outlay of time with the HB and although
the technology seems tried and tested actually building the heatbank
and commissioning it is something of an act of faith as they are not
an everyday domestic item.
So some more questions:
I need more info in the PHE please.
Who would you say make the most reliable units and what sort of size
am I looking for?
How do I predict the flow rate for a given temperature of HW?
What is the service life of a PHE likely to be?
Great help if you could point me in the direction of more technical
data of PHEs
I think it would be best in my setting to have two smaller cylinders.
One for the CH and one for the HW.
I could site them optimally for each use and have the benefit of
greater control of each cylinder than if I were trying to make one
cylinder do both jobs. Or am I barking?
I've looked at this schematic:
hxxp://aycu27.webshots.com/image/38786/2000028197462625313_rs.jpg
and taken on board DD's tweeks to the design. It looks very
buildable. My only concern would be pump noise and what *exactly* the
blending valve is designed to do in this cicuit. Presumably if I used
two cylinders I'd need another blending valve and they would be set at
different temps because (I assume) the CH cylinder is likely to be at
a lower temp setting that the HW one.
That's all for now. Thank you again for this thread.
Frank.
John Rumm
> However, I suspect that the actual saving either way (HB or combi) are
> fairly minimal. It's more a question of initial outlay, system
Yup. It is the way you need to look at it, although DD will argue to the
contrary, you can't really claim that a HB solution will save much if
any money over directly driven rads with a modern boiler - the numbers
just don't support it. Hence it needs to come down to what else it buys
you, and is that something worth paying for.
> flexibility, ease of servicing and future proofing (ie electric
Ease of servicing is partly down to what facilities you design in, and
how simple the system is in the first place.
> immersion back up or solar energy when the Russians cut off the gas).
> Many of the boxes are ticked by a heat bank - perhaps a few more than
Yup, a heatbank is handy when you want to aggregate different sources of
heat - especially if some of those are "low grade" heat.
> the combi. There is a greater outlay of time with the HB and although
> the technology seems tried and tested actually building the heatbank
> and commissioning it is something of an act of faith as they are not
> an everyday domestic item.
>
> So some more questions:
>
> I need more info in the PHE please.
> Who would you say make the most reliable units and what sort of size
> am I looking for?
I take it you are talking about a PHE used for on the fly HW heating
from the store rather than one used for isolating a vented store from a
sealed primary?
Size is the easier one, you can work that one back from your HW flow
rate requirements. So say you want 25 lpm of water at a final temp of 50
degrees, and this is to happen with the ground water at 5 degrees, you
need to shift 4200 x 45 x 25 = 4.7MJ / min or 78kJ/sec aka kW. So 80kW
or better would be required here.
> How do I predict the flow rate for a given temperature of HW?
rearrange the above formula...
So for a given PHE power of P, a temperature rise of Td, you get a flow
rate F of:
P x 60
F = ---------
4200 x Td
will give a flow in kg/min or litres
> What is the service life of a PHE likely to be?
How hard is your water?
> Great help if you could point me in the direction of more technical
> data of PHEs
GEA have a fair bit of info on their site:
> I think it would be best in my setting to have two smaller cylinders.
> One for the CH and one for the HW.
>
> I could site them optimally for each use and have the benefit of
> greater control of each cylinder than if I were trying to make one
> cylinder do both jobs. Or am I barking?
You are running counter to your requirement for simplicity and
serviceability. The only particular advantage it addresses is location
close to point of use. Note that only really matters for HW production
- you probably are not going to care if the rads need another 20 secs to
get hot.
Doctor Drivel
"John Rumm" <see.my.s...@nowhere.null> wrote in message
> frank...@hotmail.co.uk wrote:
>
>> However, I suspect that the actual saving either way (HB or combi) are
>> fairly minimal. It's more a question of initial outlay, system
>
> Yup. It is the way you need to look at it, although DD will argue to the
> contrary, you can't really claim that a HB solution will save much if any
> money over directly driven rads with a modern boiler - the numbers just
> don't support it.
What numbers do you have? None at all. You are making this up.
>> flexibility, ease of servicing and future proofing (ie electric
>
> Ease of servicing is partly down to what facilities you design in, and how
> simple the system is in the first place.
A heat bank using a simple boiler, time clock in one location, Smart pumps
in one location for each zone is: simple, easy to maintain and cheap to run
and maintain.
>> immersion back up or solar energy when the Russians cut off the gas).
>> Many of the boxes are ticked by a heat bank - perhaps a few more than
>
> Yup, a heatbank is handy when you want to aggregate different sources of
> heat - especially if some of those are "low grade" heat.
>
>> the combi. There is a greater outlay of time with the HB and although
>> the technology seems tried and tested actually building the heatbank
>> and commissioning it is something of an act of faith as they are not
>> an everyday domestic item.
They are very common indeed, maybe not around your way though. Whole
estates are fitted with them.
>> So some more questions:
>>
>> I need more info in the PHE please.
>> Who would you say make the most reliable units and what sort of size am I
>> looking for?
DPS sell them for approx £70. Gledhill can supply. Go to their site and
download the instructions on the Systemate and the the part No. is in their.
Ring a local agent and they will give a price, usually around £80. Or you
may know a local dealer who supplies them. Go for a long and thin plate of
100 kW. The Swep that Gledhill use is very good for efficiency. The Danfoss
double pass plates which are great but expensive.
>> What is the service life of a PHE likely to be?
>
> How hard is your water?
Large plate resist scale as the plates flex, so scaling is not an issue wuth
them. Not the case on small plates used in many combis. Best use a 100kW
plate as the plates are larger. 20 years minimum should be the expect life
of a quality plate.
>> Great help if you could point me in the direction of more technical
>> data of PHEs
>
> GEA have a fair bit of info on their site:
>
> http://www.gea-ecoflex.de/
http://www.heatweb,com
have some details on plates too.
>> I think it would be best in my setting to have two smaller cylinders.
>> One for the CH and one for the HW.
>>
>> I could site them optimally for each use and have the benefit of
>> greater control of each cylinder than if I were trying to make one
>> cylinder do both jobs. Or am I barking?
You are on the right track.
> You are running counter to your requirement for simplicity and
> serviceability.
He isn't at all. He is dividing and ruling, separating the functions and
optimising each. Easy to work on, maintain and greater efficiency. The ch
buffer will be completely off in the summer. With all the zones he has a ch
buffer is ideal, and acts as a large neutral point and header combined. A
dual temperature boiler with an integrated weather compensator will keep the
CH buffer at what the outside temperature dictates and rise to heat the DHW
heat bank. Have DHW priority in heating the cylinders, using a 3-way
"diverter" valve at the boiler. CH calling? Full boiler heat to the DHW
cylinder. DHW satisfied and CH calling? The weather compensator takes
control of cylinder temperature.
Doctor Drivel
<frank...@hotmail.co.uk> wrote in message
news:0c6409e4-469b-4212...@v4g2000hsf.googlegroups.com...
> I've looked at this schematic:
>
> hxxp://aycu27.webshots.com/image/38786/2000028197462625313_rs.jpg
>
> and taken on board DD's tweeks to the design. It looks very
> buildable. My only concern would be pump noise and what *exactly* the
> blending valve is designed to do in this cicuit.
The blending valve's function is explained in this thread.
It guarantees the highest temperature set so only very hot water enters the
store at the top of the cylinder ready for use to give useful DHW, even
after 2 minutes of running from cold a sink can be filled. It also
guarantees the boiler is operating within its delta T (flow/return temp
difference) and maximises thermal expansion. It guarantees top down heating
of the store and the water is heater one pass of the boiler quickening the
re-heat - this can mean a smaller cylinder in many cases as the energy of
the boiler and cylinder are combined. It also increases boiler longevity as
the boiler is operating in an ideal hydraulic environment.
> Presumably if I used two cylinders I'd need
> another blending valve and they would be set at
> different temps because (I assume) the CH
> cylinder is likely to be at
> a lower temp setting that the HW one.
No. Only one blending valve for DHW. The ch buffer cylinder doesn't need
it.
frank...@hotmail.co.uk
Thanks to both JR and DD for their further comments. I'll get my head
round the PHE info later on.
One thing DD said though had me a bit foxed. The weather compensator
makes plenty of sense. CAn they be wired into any boiler - such as
the Glow Worm you suggested or do I have to be careful to get one that
will cope?
Also 'Dual temperature boiler'? I think I can imagine what that is
but clarification would help. Sounds good - do I have to be careful
what I choose or can they all be made to do it?
Thanks again,
Frank
Doctor Drivel
<frank...@hotmail.co.uk> wrote in message
news:b30536bf-ffd2-45da...@n20g2000hsh.googlegroups.com...
> Frank here again.
>
> Thanks to both JR and DD for their further comments. I'll get my head
> round the PHE info later on.
>
> One thing DD said though had me a bit foxed. The weather compensator
> makes plenty of sense. CAn they be wired into any boiler - such as
> the Glow Worm you suggested or do I have to be careful to get one that
> will cope?
A weather compensator can be a stand alone device. Danfoss used to make a
cheap one.
Many boilers now have them integrated. Keston, Atmos, even a cheapo BIASI
model too.
> Also 'Dual temperature boiler'? I think
> I can imagine what that is but clarification
> would help. Sounds good - do I have to be careful
> what I choose or can they all be made to do it?
There are a few a round. The MAN comes to mind as well. Even a Ravenheat
does this too - not sure if it has a compensator though.
The Keston Qudos is dual temperature.
http://tinyurl.com/257dae This is cheap for what it is.
The manual can be downloaded from,
http://www.keston.co.uk
The DHW sensor/stat is wired into the boiler. When DHW is called it runs up
to max temp (or what you select), when no DHW and CH called then it reverts
to weather compensator control
The Atmos Intergas has similar specs, except I don't think it is duel
temperature. This can usually be done by opening, or shorting the outside
sensor making the burner run full on. Then it can be used to reheat DHW
fast. Best see the makers on how get around it. Atmos are super reliable
and very well made
http://www.atmos.uk.com/product_group.asp?section=000200130003
The installation manual is also on line too.
Many of these boilers have a laptop interface so you can see how the boiler
is performing.
frank...@hotmail.co.uk
A first look at the installation guide etc. for the Keston Kudos is
very promising. A whole load of functionality for around the same
price mark as other less handy looking machines. I like the wiring
being external and proper diagrams in the guide etc.
Are Kestons well thought of in terms of value and reliability?
Two other things at this stage I would like comments on please:
1) It looks as thought the pump sending HW to the PHE from the
cylinder is either on or off. When load on the DHW is light does this
not mean that quite hot water is sent back t the bottom of the
cylinder and disadvantageously admixed with the colder water there? I
presume that the flow switch in the mains supply is either on or off
and likewise the Grunfos.
2) Using a direct cylinder for the CH heatbank may be the most
efficient but risks grot from the rads getting into the boiler. Is
the magnaclean generally though to be adequate? I suppose one could
put a PHE between the boiler and the DHW cylinder but there comes a
point...
Thought please.
Frank
Doctor Drivel
<frank...@hotmail.co.uk> wrote in message
news:8ffa308a-3023-4c53...@l32g2000hse.googlegroups.com...
> From Frank
>
> A first look at the installation guide etc. for the Keston Kudos is
> very promising. A whole load of functionality for around the same
> price mark as other less handy looking machines. I like the wiring
> being external and proper diagrams in the guide etc.
>
> Are Kestons well thought of in terms of value and reliability?
They are generally fine. The Celsuis was a dog, but by the time they got rid
of the problems they dropped it. This appears a dropped down commercial
boiler with parts from other reliable boilers. It can also have 60 metres
of plastic flue pipe (normal drain pipe).
> Two other things at this stage I would like comments on please:
>
> 1) It looks as thought the pump sending HW to the PHE from the
> cylinder is either on or off. When load on the DHW is light does this
> not mean that quite hot water is sent back t the bottom of the
> cylinder and disadvantageously admixed with the colder water there? I
> presume that the flow switch in the mains supply is either on or off
> and likewise the Grunfos.
That is the case. Having spreader pipes prevents excessive disturbance of
stratification.
> 2) Using a direct cylinder for the CH heatbank may be the most
> efficient but risks grot from the rads getting into the boiler. Is
> the magnaclean generally though to be adequate?
Yes.
> I suppose one could
> put a PHE between the boiler and the DHW cylinder but there comes a
> point...
>
> Thought please.
The Magnaclean is all you need. And just re-dose the system every 4 years
with inhibitor.
Doctor Drivel
<frank...@hotmail.co.uk> wrote in message
news:8ffa308a-3023-4c53...@l32g2000hse.googlegroups.com...
> From Frank
>
> A first look at the installation guide etc. for the Keston Kudos is
> very promising. A whole load of functionality for around the same
> price mark as other less handy looking machines. I like the wiring
> being external and proper diagrams in the guide etc.
>
> Are Kestons well thought of in terms of value and reliability?
>
> Two other things at this stage I would like comments on please:
There was a thread on the Keston a few weeks back.
frank...@hotmail.co.uk
You said 'That is the case. Having spreader pipes prevents excessive
disturbance of
stratification.'
As I understand it a spreader pipe in inserted through the lower
flange and has holes drilled below and to the sides. Presumably if
this is warmer than the water at the bottom it will pass up through it
and with it. So - if I am picturing this correctly - there must be
mixing and disruption of the stratification. How much of problem is
this to efficiency? Are there any other ways of reducing the mixing?
Or is it not a problem?
Waiting to hear back from the Gledhill rep how much for the PHE
I wonder what size the cylinders should be.
Look forward to hearing your further thoughts.
Frank
John Rumm
>>> However, I suspect that the actual saving either way (HB or combi) are
>>> fairly minimal. It's more a question of initial outlay, system
>>
>> Yup. It is the way you need to look at it, although DD will argue to
>> the contrary, you can't really claim that a HB solution will save much
>> if any money over directly driven rads with a modern boiler - the
>> numbers just don't support it.
>
> What numbers do you have? None at all. You are making this up.
I already gave you an example.
If you look at the (externally verified and tested) specs of many modern
boilers, you will note they will run at about 92%+ efficiency into a
conventional radiator setup with room stat interlock and TMVs on the non
room stat rads. (SEDBUK values typically adjust this down to 90% taking
into account seasonal influences)
Note that this is a real efficiency figure calculated using the gross
energy content of the gas - none of your "make believe 106% no use to
man nor beast" style efficiencies. So any amount of extra complexity you
decide to glue between your boiler and radiators, is not going to be
able to raise the efficiency by more than 5% at best.
Back in the days of high water content fixed output boilers with dumb
controls, the store may have made a notable difference in efficiency,
and been well worth having on fuel consumption grounds alone. That is no
longer the case.
So by all means use a store if it gets you other facilities that you
desire, just don't be mislead into thinking it will save you any
significant money
frank...@hotmail.co.uk
Most parts seem easy enough to get hold of but there are two items
I've little experience of.
Flow switch and blending valve.
Any recommendations of makes that have been found reliable and good
value by others?
Many thanks,
Frank
John Rumm
> Most parts seem easy enough to get hold of but there are two items
> I've little experience of.
>
> Flow switch and blending valve.
(the reed switch versions ought to be very reliable as long as you make
sure you don't overload the contacts)
> Any recommendations of makes that have been found reliable and good
> value by others?
Screwfix and BES both have blending valves. Can't tell you which is
better though.
frank...@hotmail.co.uk
Thanks for all that.
Should manage a proper schematic and costing of my proposed system in
the next day or two and then bound to have a few more questions.
Thanks again for all the above information.
Frank
Doctor Drivel
<frank...@hotmail.co.uk> wrote in message
news:b2cdb7d0-2caf-4830...@u10g2000prn.googlegroups.com...
Here is how to do a DHW only heat bank and the parts...
Read http://www.heatweb.com for an explanation of how heat banks work.
1. Fit a Surrey type of flange in the top tapping of cylinder. 1" if you
can.
2. The plate heat exchanger connects to the Surrey flange port that is
immersed in the cylinder water. Drill a few holes in the protruding tube
that goes into the water to ensure heat is extracted from cylinders dome,
not being pumped to the bottom of the cylinder. The protruding tube has a
plate over the end to stop the water heat right to the bottom of the
cylinder.
3. The boiler flow is taken from the other connection of the Surrey flange
on the top of the cylinder. The return into the old cold feed tapping.
4. From the Surrey to the plate and then to the pump then to a spring loaded
check valve and back into the bottom cylinder port. Make a diffuser by
inserting 22mm pipe into the bottom cylinder port and drilling holes in and
stopping up the end with an internal pipe stop (available from BES). File
down the inside of a brass compression fitting that screws to the cylinder
port, removing the pipe stop so the pipe can go straight through. This will
spread the returning water mainly down, so it will not upset stratification
in the cylinder.
5. Two cylinder stats can be used to give a long efficient boiler recovery
burn. One stat about half way up and the other about 25% of the way up the
cylinder. Set bottom say to 70-80C, set top say to 60-65C. The stats must be
latched in with a relay.
6. The cold mains direct from the cold mains stoptap with no tee offs. Take
into the flow switch then into the bottom connection of the plate heat
exchanger and then to the DHW blending valve.
7. Have thermostatic shower mixers and take the hot supply for these
directly off the plate heat exchanger "before the TMV (blending valve). No
need to run DHW through two thermostatic mixers.
8. Install a phosphor de-scaler, or other de-scaler, on the incoming mains
pipe.
9. Install isolation valves on heavy usage appliances such as the washing
machine, and throttle back so it will not rob showers and baths of hot
water.
10. Have the F&E tank top up at the bottom of the cylinder and vent at the
top. You may want to vent from the boiler flow pipe.
11. Fill with inhibitor - about 1% of total system volume. An average system
is approx 100 litres, so a system has one 1 litre can. If say 150 litre
cylinder then two cans for the cylinder alone, which is three.
12. Fit a Magnaclean filter on the rads return pipe to the boiler.
The performance is brilliant and you will be delighted with the mains fed
showers and no vibrating power shower pump noise. High pressure mixers can
be on all appliances.
Gledhill will supply a Plate Heat X. The model for the 145 litre Systemate
will do. If you can get another cheaper source then try them. A 100kW plate
heat exchanger is needed
<http://www.bes.co.uk> or Screwfix will supply most of the fittings. They
don't do the plate heat exchangers.
Farnell will supply the flow switch <http://www.farnell.co.uk> Farnell
number: 1006771 with 22mm compression joints.
Flow Switch, makers site: The FS06
http://www.gentechsensors.com/productTemplate.asp?ProdId=113
This flow switch is about the best - very good.
If the boiler requires to be in a sealed system then have a cylinder with a
quick recovery coil, the boiler heats this ASAP. Most boilers can be fitted
to an open vented system. Best have open vented.