Weather compensation boiler controls?
Lobster
fitted with weather compensation controls.
I'm still waiting for the engineer's quote for this but am confident
it's going to be very expensive. My question is, to which I'm unable to
find an answer, is what sort of fuel savings is this likely to make?
Although our gas bills in this old and poorly insulated property are
sky-high, I'm sure it won't make economic sense to fit this gizmo unless
it makes a reasonably substantial saving. All th blurb I can find is
very cagey on this point.
(I'm going for a W-B 30CDi system boiler, and this is the weather
compensation device:
<http://www.worcester-bosch.co.uk/cache/file/289/fw100-installation-and-user-instructions.pdf>
Secondly, the engineer's pointed out that if I have this fitted, I need
to be aware that the boiler will always prioritise HW over CH, so it can
take quite some time for the CH to kick in if the HW is sold. (I think
this is due the tio the diverter valve it needs? not sure). How much of
a real problem is this?; but anyway I thought that was how all/most
systems operate?
Thanks for any advice
David
Guy Dawson
> Further to another thread, I've been looking into having my new boiler
> fitted with weather compensation controls.
What does the weather compensation control actually do? Which part of
the system's operation is changed and how is it changed?
> My question is, to which I'm unable to
> find an answer, is what sort of fuel savings is this likely to make?
> Although our gas bills in this old and poorly insulated property are
> sky-high,
That sort of building is always going to be expensive to heat.
> I'm sure it won't make economic sense to fit this gizmo unless
> it makes a reasonably substantial saving.
Indeed.
> All th blurb I can find is very cagey on this point.
To the cynic in my that suggests the savings are not great!
Guy
-- ---------------------------------------------------------------------
Guy Dawson@SMTP - gn...@cuillin.org.uk // ICBM - 6.15.16W 57.12.23N 986M
4.4>5.4 4.4>5.4 4.4>5.4 The Reality Check's in the Post! 4.4>5.4 4.4>5.4
Dave Liquorice
> My question is, to which I'm unable to find an answer, is what sort of
> fuel savings is this likely to make? Although our gas bills in this old
> and poorly insulated property are sky-high,
I doubt it'll make much difference, heat loss is heat loss. I can't
make out from the .pdf you linked to if it (or the boiler) has
connections for tank and room stats, it wibbles about running the DHW
pump so many times/hour Why does it need to do that? If there is a
tank stat that will be telling the system if the DHW is hot or not,
does it need to run the pump to extract heat (and waste it...) from
the cylinder to know if the DHW is still hot?
Personally well a insulated tank with tank stat and programable room
stat with some TRVs will give a pretty effcient system. I doubt
adding weather compenstation would add very much saving.
Upping the insulation and/or draft proofing will be far better so you
don't lose the heat you have put into the place.
--
Cheers
Dave.
Dave Plowman (News)
Lobster <davidlobs...@hotmail.com> wrote:
> Further to another thread, I've been looking into having my new boiler
> fitted with weather compensation controls.
> I'm still waiting for the engineer's quote for this but am confident
> it's going to be very expensive.
If the boiler is designed for this, the only additional expense is the
outside sensor and wiring. Make sure it goes in a shaded north facing
position.
> My question is, to which I'm unable to
> find an answer, is what sort of fuel savings is this likely to make?
> Although our gas bills in this old and poorly insulated property are
> sky-high, I'm sure it won't make economic sense to fit this gizmo unless
> it makes a reasonably substantial saving. All th blurb I can find is
> very cagey on this point.
I have a Viessmann with weather compensation. Sadly can't give any real
figures over the old system as the gas price went up so much round about
the time I fitted it. Suppose I could look at actual gas usage if I could
be bothered. ;-)
> (I'm going for a W-B 30CDi system boiler, and this is the weather
> compensation device:
<http://www.worcester-bosch.co.uk/cache/file/289/fw100-installation-and-user-instructions.pdf>
> Secondly, the engineer's pointed out that if I have this fitted, I need
> to be aware that the boiler will always prioritise HW over CH, so it can
> take quite some time for the CH to kick in if the HW is sold. (I think
> this is due the tio the diverter valve it needs? not sure). How much of
> a real problem is this?; but anyway I thought that was how all/most
> systems operate?
Not noticed it with mine - but then the old system was designed for hot
water priority too.
I would say setting up the software for weather compensation is pretty
complicated and needed several goes to get right. That would be expensive
if paying someone to do it.
--
*It doesn't take a genius to spot a goat in a flock of sheep *
Dave Plowman da...@davenoise.co.uk London SW
To e-mail, change noise into sound.
The Natural Philosopher
> Further to another thread, I've been looking into having my new boiler
> fitted with weather compensation controls.
>
> I'm still waiting for the engineer's quote for this but am confident
> it's going to be very expensive. My question is, to which I'm unable to
> find an answer, is what sort of fuel savings is this likely to make?
> Although our gas bills in this old and poorly insulated property are
> sky-high, I'm sure it won't make economic sense to fit this gizmo unless
> it makes a reasonably substantial saving. All th blurb I can find is
> very cagey on this point.
>
Indeed. Look, in an older property, there are usually far more effective
things to do first.
All a very excellent control system can do is to minimise *overheating*.
Basically that means getting a more even heat, and especially at floor
level - UFH can run a room a couple of degrees cooler and it still feels
as warm.and also with poorly insulated walls, the 'rad' is well away
from the walls..making sure rooms don't overshoot, by turning down the
boiler BEFORE the rooms are quite warm..that's very useful if you have a
lot of masonry and want to run on a timer,
BUT if my experience is anything to go by, all that means is that maybe
you get to run a couple of degrees colder overall - so say 18C instead
of 20C. Since the majority of the heat is needed when its down around
zero outside, that, at best, means a gain of 10%.
Draughtproofing and proper insulation can net you a 300% gain.
> (I'm going for a W-B 30CDi system boiler, and this is the weather
> compensation device:
> <http://www.worcester-bosch.co.uk/cache/file/289/fw100-installation-and-user-instructions.pdf>
>
>
> Secondly, the engineer's pointed out that if I have this fitted, I need
> to be aware that the boiler will always prioritise HW over CH, so it can
> take quite some time for the CH to kick in if the HW is sold. (I think
> this is due the tio the diverter valve it needs? not sure). How much of
> a real problem is this?; but anyway I thought that was how all/most
> systems operate?
>
not really. I have twin valves, so I can run HW and CH together.
OK the boiler isn't entirely up to that, so it tends to slog for an hour
doing both, in very cold weather, but it does DO both together.
> Thanks for any advice
I think if you are looking for best return in reduced heating bills, you
had best tell us what you have now, in terms of room sizes and
construction, and what its costing you.
I've spent nearly a grand tanking up the oil for the winter. I hope it
lasts. I am not running any central heating beyond an 800W 24x7 Aga,
which is so far enough.
That will change soon. December January and February will empty a 2500
liter tank of oil.
And the insulation is good, but its a big house.
Insulation, insulation, insulation.
For a detached rural house, I think a target for heating should be about
£1 per sq ft per annum.
If you are significantly above that, then time to think insulation.
My ownn rule of thumb for cost benefit in decsinding value for money is...
0/. learn to wear a jumper and thick socks..
1/. draught proof.
2/. loft/pipe insulate
3/. wall insulate
4/. double glaze
5/. floor insulate
6/. upgrade heating system
7/. go fancy on boilers and thermostats and zones.
Of course, if you have draughty rotten crumbling window frames, then you
might do 4 as part of 1 at not much extra cost.
> David
John Rumm
> Further to another thread, I've been looking into having my new boiler
> fitted with weather compensation controls.
>
> I'm still waiting for the engineer's quote for this but am confident
> it's going to be very expensive. My question is, to which I'm unable to
> find an answer, is what sort of fuel savings is this likely to make?
The basic thrust of your question is sound - as you have probably
realised a modern condenser is already >90% efficient (seasonally
adjusted) when driving the rads and providing hot water. In fact the
boiler efficiency can push 96% efficiency in an ideal environment if you
have a boiler that condenses all the time at its maximum rate (note some
combis don't condense at all in HW mode).
Historically, weather compensation minimised overheating, kept more
stable temperatures and improved comfort. These days it still does that,
but it also allows the boiler to operate with greater condensing
efficiency. So the energy savings come into two categories; firstly it
pushes the boiler to operate closer to its theoretical maximum
condensing efficiency by matching flow temperatures to what is actually
required (so lower average return temperatures) at any given time,
rather than defaulting to what would be required on really cold days,
and secondly it slightly reduces the total energy input by eliminating
the overshoots you would normally get.
Putting numbers to this is harder. However, basic arithmetic tells you
the first number will be less than 6%. So in reality a guestimate of say
half to two thirds of that may be realistic 3% - 4%. The second one is a
harder call, since it will be more dependent on nature of the building.
Historically, manufacturers made claims of reductions in fuel use of up
to 15%. That is probably not a realistic realistic gain when measured
against a modern boiler with a modern electronic prog stat, but perhaps
half that is[1]. So if you assumed something like 10% overall from
reclaiming the last easily accessible vestiges of efficiency from the
boiler itself, and eliminating unnecessary heating you would be in the
right ball park.
[1] You might get more in a particularly leaky building, since it will
tend to have more heating / cooling cycles in a given time.
> Although our gas bills in this old and poorly insulated property are
> sky-high, I'm sure it won't make economic sense to fit this gizmo unless
> it makes a reasonably substantial saving. All th blurb I can find is
> very cagey on this point.
If the choice were money spent on extras or extra insulation, then the
insulation would be first choice probably. Unless you were installing
the stuff yourself, in which case the parts alone are not that expensive
(although the need for the diversion kit does make it more expensive).
(as you are probably aware, I am in a similar boat myself. With some of
the boilers I have been looking at, the weather compensation is needed
to allow split temperature operation, and to interface to multiple zones
etc - so it was a pre-requisite. Also in many cases the cost difference
is marginal say �90 for the compensator, vs �50 for a more mundane
control, so the capital recovery time would be minimum at my current gas
usage).
> (I'm going for a W-B 30CDi system boiler, and this is the weather
> compensation device:
> <http://www.worcester-bosch.co.uk/cache/file/289/fw100-installation-and-user-instructions.pdf>
>
>
> Secondly, the engineer's pointed out that if I have this fitted, I need
> to be aware that the boiler will always prioritise HW over CH, so it can
> take quite some time for the CH to kick in if the HW is sold. (I think
That's only partly true - the FW100 acts as a programmer for the HW -
and you can dictate at what times the HW is allowed to heat. Only during
those times should it then take priority.
> this is due the tio the diverter valve it needs? not sure). How much of
> a real problem is this?; but anyway I thought that was how all/most
> systems operate?
Its probably not an issue in reality if you chose your times and
settings carefully. Also if you HW recovers fairly quickly, it will not
amount to much interruption time wise.
--
Cheers,
John.
/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/
Rick Hughes
"Lobster" <davidlobs...@hotmail.com> wrote in message
news:s0dDm.65932$Rj7....@newsfe28.ams2...
> Further to another thread, I've been looking into having my new boiler
> fitted with weather compensation controls.
>
> (I'm going for a W-B 30CDi system boiler, and this is the weather
> compensation device:
> <http://www.worcester-bosch.co.uk/cache/file/289/fw100-installation-and-user-instructions.pdf>
>
These were tested quite a lot and found not suitable for domestic install
.... to compensate they have to react to external weather sensor ... so as
it's getting cold outside it fires up boiler earlier.
OK .. so where do you put sensor ? ... on South side ,,, in which case sun
could turn off heating too early, or North facing and it could remain in
shade & cold blissfully turning heating on in the house.
You would need multiple sensors and averaging circuitry to give good
compensation control on house.
OK in commercial install ... where you might put a sensor on each corner of
a larger building ... but overkill for a house.
Far better to well insulate, design with multiple zones and have digital
stats on each zone .... I have 14 zones, no on/off, just different temp at
different times of the day ... result a very high level of comfort.
Donwill
an externally mounted (North Wall) temperature sensor. No extra
programming, just connect in the appropriate terminals and all it does
is to alter the water temperature according to external air temperature.
In practice a very comfortable even temp in the house. The compensation
control is done by the separate Danfoss timer/ thermostat and fires up
the boiler earlier on cold mornings, it claims to self learn by
monitoring the inside temp. I've no idea what difference it makes to
energy consumption.
Don
Donwill
the AQ6000 in the previous house.
Re the 5000, It does not claim to self learn, the user has to set the
warm up time to match the building energy characteristics.
Don
Lobster
> Lobster wrote:
>
>> Further to another thread, I've been looking into having my new boiler
>> fitted with weather compensation controls.
>>
>> I'm still waiting for the engineer's quote for this but am confident
>> it's going to be very expensive. My question is, to which I'm unable
>> to find an answer, is what sort of fuel savings is this likely to make?
>
> The basic thrust of your question is sound - as you have probably
> realised a modern condenser is already >90% efficient (seasonally
> adjusted) when driving the rads and providing hot water. In fact the
> boiler efficiency can push 96% efficiency in an ideal environment if you
> have a boiler that condenses all the time at its maximum rate (note some
> combis don't condense at all in HW mode).
Thanks very much for all the replies.
Certainly I realise that any savings I make on gas will be secondary to
whatever I could make by improving the insulation to the property, which
is something I'm doing when and where possible. Not easy though as it's
all solid walls and dormer roofs here and it's major upheaval to do
anything much. I just felt that if I was installing a new CH system to
last X years I don't want to fit something I regret Y years down the
line though.
I reckon it will be fairly costly to install the weather compensation
system particularly as apparently it (well, my choice does) needs this
built-in divertor valve which takes the place of existing valves in the
airing cupboard (a long way from the boiler location, with stairs
intervening), so there's a reasonable amount of carpet/floor
lifting/aggro to install new pipework. Getting thoroughly cold and
hacked off with my plumber's inability to provide a quote for fitting
this kit any time soon, so have decided to forget it and stick with
conventional controls!
David
John Rumm
> Thanks very much for all the replies.
>
> Certainly I realise that any savings I make on gas will be secondary to
> whatever I could make by improving the insulation to the property, which
> is something I'm doing when and where possible. Not easy though as it's
> all solid walls and dormer roofs here and it's major upheaval to do
Yup, same here. I concluded I am going to have to insulate the outside
rather than the inside - it will be less hassle and mess and also will
place the bulk of the thermal mass inside the insulated envelope.
> anything much. I just felt that if I was installing a new CH system to
> last X years I don't want to fit something I regret Y years down the
> line though.
Much depends on how much you are paying for gas, and also what you are
replacing. On my place I estimate the payback period in gas savings
alone will be about 4 years worst case, (annual has bill probably �1300
- �1500). The current setup is unlikely to push 70% efficiency -
probably closet to 65%. So being conservative, that is �300/year in gas
if I moved to something about 90% efficient.
> I reckon it will be fairly costly to install the weather compensation
> system particularly as apparently it (well, my choice does) needs this
> built-in divertor valve which takes the place of existing valves in the
> airing cupboard (a long way from the boiler location, with stairs
> intervening), so there's a reasonable amount of carpet/floor
> lifting/aggro to install new pipework. Getting thoroughly cold and
> hacked off with my plumber's inability to provide a quote for fitting
> this kit any time soon, so have decided to forget it and stick with
> conventional controls!
Do you have to go for that boiler? Many of the others I have looked at
can drive a conventional zone valve[1] near the cylinder - and hence
re-use the existing flow and return pipework - it would not be much
cheaper in terms of parts, but would save lots of extra pipework.
[1] Although to be fair some like the Vaillant need an interface box of
tricks at about �60 to do so.
Doctor Drivel
"Rick Hughes" <rick_...@btconnect.com> wrote in message
news:yOudnXZATOmIIEDX...@bt.com...
>
> "Lobster" <davidlobs...@hotmail.com> wrote in message
> news:s0dDm.65932$Rj7....@newsfe28.ams2...
>> Further to another thread, I've been looking into having my new boiler
>> fitted with weather compensation controls.
>>
>
>> (I'm going for a W-B 30CDi system boiler, and this is the weather
>> compensation device:
>> <http://www.worcester-bosch.co.uk/cache/file/289/fw100-installation-and-user-instructions.pdf>
>
> These were tested quite a lot and found not suitable for domestic install
> .... to compensate they have to react to external weather sensor ... so as
> it's getting cold outside it fires up boiler earlier.
That is called feed-forward control. It anticipates the coming heat loss.
> OK .. so where do you put sensor ? ... on South side
North side out of the sun.
Weather compensation works brilliantly with condensing boilers as it lowers
the temperature of the boiler promoting efficiency. Especially one which is
linked to the boilers control system and modulates the burner to suit the
flow setpoint which is automatically raised and lowered by the outside
temperature sensor. Some room temperature influence. This means that, say
the flow temp is determined to be 50C by the outside sensor, and the temp
inside the house climb up to the house setpoint of say 21C. The control
system will drop the flow temperature even lower, to say, 45C, then, 40C and
so on until setpoint is reached and then off. It keeps lowering the flow
temp to keep a constant low temp injection of heat to maintain room
setpoint. This really increases comfort levels and promotes gas efficiency.
Weather compensation on domestic boilers is cheap. The Avantaplus boilers
are very good at this. The W-B 2-way valve converts the boiler into a
"dual-temperature" boiler, as is the Avantaplus. The Avantaplus boilers are
better and cheaper. Remeha (Dutch) who make the Avantaplus have just brought
out Baxi.
Doctor Drivel
"Donwill" <Donwill...@invalid.invalid> wrote in message
news:7k615bF...@mid.individual.net...
>> Thanks for any advice
>> David
> Purchased a new Combi Atmos boiler ,the weather compensation extra was an
> externally mounted (North Wall) temperature sensor. No extra programming,
> just connect in the appropriate terminals and all it does is to alter the
> water temperature according to external air temperature. In practice a
> very comfortable even temp in the house. The compensation control is done
> by the separate Danfoss timer/ thermostat and fires up the boiler earlier
> on cold mornings, it claims to self learn by monitoring the inside temp.
> I've no idea what difference it makes to energy consumption.
> Don
Atmos also do an non-combi version. Yes, the compensator is self-adaptive,
learning your house.
Doctor Drivel
"Donwill" <Donwill...@invalid.invalid> wrote in message
Use an OpenTherm compatible controller with OpenTherm controlled boiler.
Atmos, Avantaplus, Keston, etc have it. Well worth it as it seamlessly
notches into your boiler control system. OpenTherm protocol is standard on
the Continent. UK makers tend to ignore it. I don't know why.
Doctor Drivel
"The Natural Philosopher" <t...@invalid.invalid> wrote in message
news:hbk2f5$6uf$1...@news.albasani.net...
> All a very excellent control system can do is to minimise *overheating*.
It is?
< I'll have to snip the rest >
Doctor Drivel
"Dave Plowman (News)" <da...@davenoise.co.uk> wrote in message
news:50ad1c9...@davenoise.co.uk...
> I would say setting up the software for weather compensation is pretty
> complicated and needed several goes to get right. That would be expensive
> if paying someone to do it.
The Avantaplus is easy to setup.
Onetap
> Further to another thread, I've been looking into having my new boiler
> fitted with weather compensation controls.
I had a Vaillant weather compensating system fitted in October; too
early to report on savings yet.
I fitted everything myself, except the boiler because I need the Gas
Safe certificate to get a completion certificate from Building
Control. Be warned that the average installer is clueless about
electronic controls. The man who put the boiler in only does Vaillant
installs, yet he'd never seen the Vaillant WC kit I installed.
Secondly, the Vaillant controls were plug & play type in the ease of
installation. However the weather compensation seems to simply sets
the flow temperature as a function of the outdoor temperature. This is
OK when the building is at operating temperature. It is not OK when
the building is warming up. I'll have to study the manual more.
Vaillant seem to 'lock you in' to their control system; an industry
standard 0-10V control options isn't offered.
Third, the system it replaced was self built from individual
components with a motorized valve keeping PIR control of the one room
with the temperature sensor. I've got to say, the old system was far
more comfortable. The house feels colder, but I still have a couple of
radiators to connect so it may be down to that.
The comfort obtained from a reduced-temperature continuous heating is
a major advantage, rather than just savings.
> Secondly, the engineer's pointed out that if I have this fitted, I need
> to be aware that the boiler will always prioritise HW over CH, so it can
> take quite some time for the CH to kick in if the HW is sold. (I think
> this is due the tio the diverter valve it needs? not sure). How much of
> a real problem is this?; but anyway I thought that was how all/most
> systems operate?
They all do that to provide an increased temperature to the hot water
cylinder. You'd otherwise need an additional mixing valve within the
boiler (Viesmann offer such a boiler) . No great problem that I've
noticed. The heating goes off but the house doesn't instantly get
cold. The HW cylinder has never got totally cold. It may make a
difference if you have a huge HW demand.
Onetap
> Third, the system it replaced was self built from individual
> components with a motorized valve keeping PIR control of the one room
PID temperature control
Doctor Drivel
"Onetap" <One...@talk21.com> wrote in message
news:41f62bc2-f113-4ec6...@n35g2000yqm.googlegroups.com...
On 20 Oct, 06:45, Lobster <davidlobsterpot...@hotmail.com> wrote:
> Further to another thread, I've been looking into having my new boiler
> fitted with weather compensation controls.
I had a Vaillant weather compensating system fitted in October; too
early to report on savings yet.
I fitted everything myself, except the boiler because I need the Gas
Safe certificate to get a completion certificate from Building
Control. Be warned that the average installer is clueless about
electronic controls. The man who put the boiler in only does Vaillant
installs, yet he'd never seen the Vaillant WC kit I installed.
> However the weather compensation seems to simply sets
> the flow temperature as a function of the outdoor
> temperature. This is OK when the building is at
> operating temperature. It is not OK when
> the building is warming up. I'll have to study the
> manual more.
They tend to have a boost which is on full, or above what the outside temp
dictates and then when up to temp it will fall back to weather compensator
control.
> Vaillant seem to 'lock you in' to their control system;
> an industry standard 0-10V control options isn't offered.
That is why OpenTherm control protocol is better. You can use any maker that
complies with OpenTherm and it works on the boilers control system. The
Avantplus is OpenTherm as is Keston and Atmos and few others. They tend to
be Continental makes. Vaillant is German but do not offer OpenThem in the
UK.
RobertL
> Lobster wrote:
> > Further to another thread, I've been looking into having my new boiler
> > fitted with weather compensation controls.
>
> What does the weather compensation control actually do? Which part of
> the system's operation is changed and how is it changed?
On my system (an ATAG boiler) the weather compensation links the
boiler flow termperature to the outside temperature. the colder it is
outside, the hotter it makes the radiators. You can choose one out of
a family of curves and you also choose a 'ceiling' flow tempertaure
beyond which the compensation will not raise it. You can see the
curves on page 27 of the E series installation manual linked from
here:
the ATAG also does something clever with the data from the room
stats. it knows not only whether the room is up to temperature or
not, but how far below temp it is. I then adjusts the "bursts" of
heat so it comes up to temp and stop rather than overshooting. it
seems to work well.
Robert
Doctor Drivel
"RobertL" <rober...@yahoo.com> wrote in message
news:e621c941-22a9-4dd8...@p8g2000yqb.googlegroups.com...
On Oct 20, 7:33 am, Guy Dawson <gn...@cuillin.org.uk> wrote:
> Lobster wrote:
> > Further to another thread, I've been looking into having my new boiler
> > fitted with weather compensation controls.
>
> What does the weather compensation control actually do? Which part of
> the system's operation is changed and how is it changed?
On my system (an ATAG boiler)
<<<
Quality indeed.
David
> fitted with weather compensation controls.
>
> I'm still waiting for the engineer's quote for this but am confident
> it's going to be very expensive. My question is, to which I'm unable to
> find an answer, is what sort of fuel savings is this likely to make?
> Although our gas bills in this old and poorly insulated property are
> sky-high, I'm sure it won't make economic sense to fit this gizmo unless
> it makes a reasonably substantial saving. All th blurb I can find is
> very cagey on this point.
>
> (I'm going for a W-B 30CDi system boiler, and this is the weather
> compensation device:
>
> Secondly, the engineer's pointed out that if I have this fitted, I need
> to be aware that the boiler will always prioritise HW over CH, so it can
> take quite some time for the CH to kick in if the HW is sold. (I think
> this is due the tio the diverter valve it needs? not sure). How much of
> a real problem is this?; but anyway I thought that was how all/most
> systems operate?
>
> Thanks for any advice
> David
I doubt it would suit an old house with poor insulation.
We have a Vaillant boiler with a Honeywell CM927 in our old house and
it works very well and the temperature is kept very steady.
Roger Chapman
>
> "The Natural Philosopher" <t...@invalid.invalid> wrote in message
> news:hbk2f5$6uf$1...@news.albasani.net...
>
>> All a very excellent control system can do is to minimise *overheating*.
>
> It is?
That depends on what view the control designer has of an ideal system.
It should be possible to design a system that never overshoots but the
cost would be in taking longer in zeroing in on the set temperature. The
more money you throw at the design the more accurate the control and the
quicker the response but, other things being equal, no overshoot equals
slower.
Weather compensation is probably the cheap way of introducing extra
heating when it is cold outside but but in theory at least it should be
perfectly possible to get first class temperature control by looking no
further than the rate of change of the internal temperature.
Onetap
> Weather compensation is probably the cheap way of introducing extra
> heating when it is cold outside but but in theory at least it should be
> perfectly possible to get first class temperature control by looking no
> further than the rate of change of the internal temperature.
Yeah but, for one building, the rate of heat loss ( through the fabric
and by ventilation) depends mostly on the outside air temperature. A
change in To will take some time to register on the internal room
temperature sensor, by causing a drop in the room temperature. It will
then take some time for the heating to respond and bring the internal
temperature back to the set point. Weather Compensation anticipates
this and turns the heating up or down to match the rate of heat loss.
It's more critical with high mass systems, especially UFH in screed,
which can take many hours to respond to an increase in the flow
temperature.
My previous system had cascaded control loops, looking at both To and
Ti. It worked very well, eventually ;-). However I cocked up the I and
D control parameters so the control valve was continually moving. It
wore the gland out & started leaking quite soon.
Owain
> My ownn rule of thumb for cost benefit in decsinding value for money is...
> 0/. learn to wear a jumper and thick socks..
> 1/. draught proof.
> 2/. loft/pipe insulate
> 3/. wall insulate
> 4/. double glaze
> 5/. floor insulate
> 6/. upgrade heating system
> 7/. go fancy on boilers and thermostats and zones.
> Of course, if you have draughty rotten crumbling window frames, then you
> might do 4 as part of 1 at not much extra cost.
and 1.5 insulate hot water cylinder if not already foamed.
Owain
Doctor Drivel
"Roger Chapman" <ro...@nospam.zetnet.co.uk> wrote in message
news:4_WdndgSJLMSS7rW...@bt.com...
> Doctor Drivel wrote:
>>
>> "The Natural Philosopher" <t...@invalid.invalid> wrote in message
>> news:hbk2f5$6uf$1...@news.albasani.net...
>>
>>> All a very excellent control system can do is to minimise *overheating*.
>>
>> It is?
>
> That depends on what view the control designer has of an ideal system. It
> should be possible to design a system that never overshoots but the cost
> would be in taking longer in zeroing in on the set temperature.
Tripe. You know nothing of self adaptive controls.
< I will will to snip the rest as it is all wrong >
Roger Chapman
>> Doctor Drivel wrote:
>>>
>>> "The Natural Philosopher" <t...@invalid.invalid> wrote in message
>>> news:hbk2f5$6uf$1...@news.albasani.net...
>>>
>>>> All a very excellent control system can do is to minimise
>>>> *overheating*.
>>>
>>> It is?
>>
>> That depends on what view the control designer has of an ideal system.
>> It should be possible to design a system that never overshoots but the
>> cost would be in taking longer in zeroing in on the set temperature.
>
> Tripe. You know nothing of self adaptive controls.
It wouldn't matter if I didn't. If you want to have enough damping to
prevent the possibility of any overshoot it will always take longer to
actually reach the set temperature than the same system with less
damping and hence the possibility at least of some overshoot.
>
> < I will will to snip the rest as it is all wrong >
Oh well, par for the course. Dribble dismissing out of hand anything he
fails to understand. Stand by for the plant pot phase of the Dribble
response to reason.
Doctor Drivel
Roger Chapman
>>>>>> All a very excellent control system can do is to minimise
>>>>>> *overheating*.
>>>>>
>>>>> It is?
>>>>
>>>> That depends on what view the control designer has of an ideal
>>>> system. It should be possible to design a system that never
>>>> overshoots but the cost would be in taking longer in zeroing in on
>>>> the set temperature.
>>>
>>> Tripe. You know nothing of self adaptive controls.
>>
>> It wouldn't matter if I didn't.
>
> Tripe. You know nothing of self adaptive controls.
That reply took you a long time to formulate given the lack of reason
behind it.
It may be over 40 years since I studied control engineering but I don't
expect the basics or the maths to have changed in the interim. The bit
you have edited out without acknowledgement - that a system damped
heavily enough to prevent overshoot will take longer to reach the set
temperature than the same system with less damping - is a basic truth
however clever the system is in predicting future behaviour on the basis
of previous observations.
Roger Mills
Roger Chapman <ro...@nospam.zetnet.co.uk> wrote:
>
> It may be over 40 years since I studied control engineering but I
> don't expect the basics or the maths to have changed in the interim.
> The bit you have edited out without acknowledgement - that a system
> damped heavily enough to prevent overshoot will take longer to reach
> the set temperature than the same system with less damping - is a
> basic truth however clever the system is in predicting future
> behaviour on the basis of previous observations.
That possibly needs some clarification - as illustrated by this Wiki article
on damping:
http://en.wikipedia.org/wiki/Critical_damping#Critical_damping_.28.CE.B6_.3D_1.29
A Critically Damped system will reach the Steady State setpoint in the
shortest time without overshoot. A less damped system will *pass* *through*
the setpoint sooner, but will continue to oscillate for longer.
So a lot depends on how you define "reach the set temperature"! There is a
sense in which you and <gritting teeth> Drivel <\gritting teeth> are both
right.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!
Roger Chapman
>> It may be over 40 years since I studied control engineering but I
>> don't expect the basics or the maths to have changed in the interim.
>> The bit you have edited out without acknowledgement - that a system
>> damped heavily enough to prevent overshoot will take longer to reach
>> the set temperature than the same system with less damping - is a
>> basic truth however clever the system is in predicting future
>> behaviour on the basis of previous observations.
>
>
> That possibly needs some clarification - as illustrated by this Wiki article
> on damping:
> http://en.wikipedia.org/wiki/Critical_damping#Critical_damping_.28.CE.B6_.3D_1.29
>
> A Critically Damped system will reach the Steady State setpoint in the
> shortest time without overshoot. A less damped system will *pass* *through*
> the setpoint sooner, but will continue to oscillate for longer.
>
> So a lot depends on how you define "reach the set temperature"! There is a
> sense in which you and <gritting teeth> Drivel <\gritting teeth> are both
> right.
I had 'first reach' in a draft but edited it out. I didn't say anything
about about remaining at set point as in order to overshoot the
temperature first has to reach set temperature. If I had known about
what was in the Wiki I might just have left it in but I doubt it.
Doctor Drivel
"Roger Mills" <watt....@googlemail.com> wrote in message
news:7ovqciF...@mid.individual.net...
> In an earlier contribution to this discussion,
> Roger Chapman <ro...@nospam.zetnet.co.uk> wrote:
>
>>
>> It may be over 40 years since I studied control engineering but I
>> don't expect the basics or the maths to have changed in the interim.
>> The bit you have edited out without acknowledgement - that a system
>> damped heavily enough to prevent overshoot will take longer to reach
>> the set temperature than the same system with less damping - is a
>> basic truth however clever the system is in predicting future
>> behaviour on the basis of previous observations.
>
>
> That possibly needs some clarification - as illustrated by this Wiki
> article on damping:
> http://en.wikipedia.org/wiki/Critical_damping#Critical_damping_.28.CE.B6_.3D_1.29
>
> A Critically Damped system will reach the Steady State setpoint in the
> shortest time without overshoot. A less damped system will *pass*
> *through* the setpoint sooner, but will continue to oscillate for longer.
>
> So a lot depends on how you define "reach the set temperature"! There is a
> sense in which you and <gritting teeth> Drivel <\gritting teeth> are both
> right.
You have to take into account that the man is mad.