Plume from heating boiler

[Pamela]

The flue from my neighbour's boiler vents a large plume, while mine is
always much smaller.

All other things being equal, does this suggest my boiler is not
condensing as mch as the neighbour's and that my boiler temperature is
too high?

[alan_m]

The reverse is true. Small plume good condensing, large plume no condensing.



--
mailto : news {at} admac {dot} myzen {dot} co {dot} uk

[Pamela]

On 11:00 4 Dec 2023, alan_m said:
> On 04/12/2023 10:53, Pamela wrote:
>>
>>
>> The flue from my neighbour's boiler vents a large plume, while mine
>> is always much smaller.
>>
>> All other things being equal, does this suggest my boiler is not
>> condensing as mch as the neighbour's and that my boiler temperature
>> is too high?
>
> The reverse is true. Small plume good condensing, large plume no
> condensing.

Doesn't the visible part of the plume consist of water vapour, and more
visible plume means more condensation is occurring?

I notice when I turn the boiler stat up high (75 celsius), there's less
visible plume.

In practical terms does the stat on my boiler need adjusting to work
more efficiently?

Government messages say turn the boiler down to 60 Celsius but mine is
usually set below that and only gets turned up above 60 in cold weather.
I am bit sceptical of following their generic advice as I believe it's
the return temperature which determines the amount of condensation and I
reckon not all systems will have the same temperature drop from what is
set on the boiler stat.

[mechanic]

On Mon, 4 Dec 2023 11:00:36 +0000, alan_m wrote:

> On 04/12/2023 10:53, Pamela wrote:
>> The flue from my neighbour's boiler vents a large plume, while mine is
>> always much smaller.
>>
>> All other things being equal, does this suggest my boiler is not
>> condensing as mch as the neighbour's and that my boiler temperature is
>> too high?
>
>
> The reverse is true. Small plume good condensing, large plume no
> condensing.

Eh? So a non condensing boiler with no plume is the right way to go?

[Andy Burns]

Pamela wrote:

> Doesn't the visible part of the plume consist of water vapour, and more
> visible plume means more condensation is occurring?

Condensation will leave via the condensate drain, rather than the flue

[Joe]

On Mon, 04 Dec 2023 11:25:56 GMT
Pamela <pamela.priv...@gmail.com> wrote:


>
> Doesn't the visible part of the plume consist of water vapour,

No. Water vapour is invisible, you're seeing condensed water droplets.

> and
> more visible plume means more condensation is occurring?

Yes, but you want that to happen inside the boiler. Condensation
releases a large amount of energy and you want to keep that inside the
house as far as possible. Any water leaving the house in vapour form is
wasted energy.

--
Joe

[Pamela]

On 12:28 4 Dec 2023, Joe said:
> On Mon, 04 Dec 2023 11:25:56 GMT Pamela
> <pamela.priv...@gmail.com> wrote:
>>
>>
>>
>> Doesn't the visible part of the plume consist of water vapour,
>
> No. Water vapour is invisible, you're seeing condensed water droplets.

Apologies. I'm getting the terminology mixed up. I should have said
"water droplets" instead of "water vapour".

>> and more visible plume means more condensation is occurring?
>
> Yes, but you want that to happen inside the boiler. Condensation
> releases a large amount of energy and you want to keep that inside the
> house as far as possible. Any water leaving the house in vapour form
> is wasted energy.

So does that mean a large visible plume (consisting of water droplets)
is a good thing?

In other words: my neighbour's large plume indicates their boiler is
running more efficiently than mine. Is this a correct understanding?

[Davey]

On Mon, 04 Dec 2023 11:25:56 GMT
Pamela <pamela.priv...@gmail.com> wrote:

A year or so ago, there were a lot of suggestions about adjusting a
condensing boiler setting that was said to instantly reduce the cost of
running the boiler. I don't have one of these, but what was this
setting, and how did it magically save money? Were there any downsides,
such as loss of microbe cooking?

--
Davey.

[Sid]

Steam is invisible, but water vapour isn't.

[The Natural Philosopher]

Of course. The ministry of Truth says so...
--
How fortunate for governments that the people they administer don't think.

Adolf Hitler

[alan_m]

On 04/12/2023 11:43, mechanic wrote:

No,

On an older non condensing boiler the flue gases can be x3 hotter than
on a condensing boiler and so take longer to cool to the required
temperature outside for a plume and dissipate before condensing.
The reason you don't tend to see the plume on a non-condensing boiler is
because you are chucking away so much energy via the flue.

[Fredxx]

On 04/12/2023 11:43, mechanic wrote:

No.

The ideal situation is where the condensing is occurring on the heat
exchanger dumping heat into the circulating water, and not outside where
it's dumping useful energy to the outside environment.

[Pamela]

This article on condensing boiler theory seems quite good and I'm
pretty sure I understood it some time ago but practice seems rather
different and I'm now back to basics!

"Condensing Theory - How Do Condensing Boilers Add Efficiency?"

https://www.heatgeek.com/condensing-boilers-efficiency/

[alan_m]

Bottom line is the whole system needs to be designed for best efficiency
and to achieve the best results a more expensive control system is
required (external temperature compensation and programmable thermostats
etc.).

[RJH]

On 4 Dec 2023 at 11:00:36 GMT, alan_m wrote:

> On 04/12/2023 10:53, Pamela wrote:
>> The flue from my neighbour's boiler vents a large plume, while mine is
>> always much smaller.
>>
>> All other things being equal, does this suggest my boiler is not
>> condensing as mch as the neighbour's and that my boiler temperature is
>> too high?
>
>
> The reverse is true. Small plume good condensing, large plume no condensing.

Hmmm. Mine - a Vaillant Ecotec combi - throws out clouds of the stuff. Keeps
triggering the PIR outside light.

It's not set especially high - CH 60c - should I turn it down to make it more
efficient?
--
Cheers, Rob, Sheffield UK

[Owain Lastname]

On Monday, 4 December 2023 at 18:33:00 UTC, RJH wrote:
> > The reverse is true. Small plume good condensing, large plume no condensing.
> Hmmm. Mine - a Vaillant Ecotec combi - throws out clouds of the stuff. Keeps
> triggering the PIR outside light.
> It's not set especially high - CH 60c - should I turn it down to make it more
> efficient?

Possibly.

Can you increase the size of your radiator load?

Owain

[RJH]

Yes, I could - a couple are turned down to about 15C. But that takes me round
in circles, heating spaces (kitchen and spare bedrooms) I don't want heating
fully. I'll try reducing the temp to say 55C.

[Davey]

snip

>
> A year or so ago, there were a lot of suggestions about adjusting a
> condensing boiler setting that was said to instantly reduce the cost
> of running the boiler. I don't have one of these, but what was this
> setting, and how did it magically save money? Were there any
> downsides, such as loss of microbe cooking?
>

Does nobody know the answer to this?

--
Davey.

[alan_m]

Just remember that the difference between not condensing and fully
condensing is around 13% in efficiency and it's impractical to get the
13% as the return flow to the boiler would have to be under 20C

With a flow of 60C your return would be of the order of <50C and
theoretically the efficiency of your boiler will be around 88%. Reducing
the flow by another 5C would give you perhaps another 1 to 2%. BUT.....

Unless your radiators are sized for 55C flow you may/will find that the
CH system does not provide enough heat for your house to be comfortable,
especially when the outside temperature is colder. You could manually
adjust the flow temperature on a week to week basis based on the outside
temperature. This is the kind of control provided by a more
sophisticated control system with weather compensation information
supplied directly to the boiler.

If your boiler is over specified for your central heating system, as
seen in one recent thread in this group, setting the flow too low will
always result in short cycling - which is far from ideal.

This thread started with a question about the size of the plume from two
boilers operating with the same outside temperature. It wasn't about one
boiler operating without a plume. What you may be seeing is normal. My
boiler tends to produce a large plume when it's just been switched on
and then settles to very minor plume once everything has settled down.
Maybe you should check when your boiler is actually producing the your
"large" plume - just after switch on? when the boiler has modulated down
and it ticking over? when the boiler fires up again after a lockout
period after a short cycle?

[alan_m]

With a condensing boiler the manufactures default setting may have been
a 75C flow temperature and with a resulting 60 to 65C return temperature
from the central heating radiator system. This would mean that the
boiler wasn't working in its condensing mode. Reducing the flow down to
60C would also reduce the return temperature putting the boiler into the
condensing mode to give perhaps 3 to 4% better efficiency.

In general, and for most of the central heating season, most people
could live with a 60C flow through their radiators.

The recommendation was carefully worded for the CH heating side of combi
boilers where no domestic hot water tank is involved.

There was/is some concern that with a hot water tank being heated by the
boiler reducing the flow temperature to the heating coil in the tank
wouldn't get the water hot enough (>60C) to kill legionella. The risk
is possibly overstated as in an occupied premises the water in the hot
water tank is always being replenished with water from the mains dosed
with Chlorine. An electric immersion heater could be switched on
perhaps once a week for a very short time to boost the boiler heated
water to above 60C. Some boilers may also have a inbuilt heating cycle
to occasionally heat water in a tank to above 60C.

[Pamela]

Last winter Martin Lewis of Money Saving Expert was tirelessly
advocating the benefits of lowering the boiler stat to save money in the
fuel crisis. Later he said although it would save money, a low boiler
temperature below 60 Celsius may not heat some properties enough and you
would have to determine your priority.

[Pamela]

On 08:55 5 Dec 2023, alan_m said:
>
> [TRIM]

>
> This thread started with a question about the size of the plume from
> two boilers operating with the same outside temperature. It wasn't
> about one boiler operating without a plume. What you may be seeing is
> normal. My boiler tends to produce a large plume when it's just been
> switched on and then settles to very minor plume once everything has
> settled down.

I was careful to compare the plume from two heating systems in two
neighbouring houses. This would mean there are not effects from
different air temperature, humidity, wind, etc. Also I have observed the
two plumes for many days on different occassions.

However, as you point out, the two heating systems may also be at
different points in their daily usage which would create their own
variance.

I'm interested because I tend to regulate the heating by varying the
boiler temperature daily, which most people wouldn't do. There are TRVs
and an portable thermostat but their settings don't reflect room comfort
as much as I would like.

[alan_m]

That's the problem with a single general recommendation. If designed
properly* most old radiator systems were designed for a flow temperature
higher than now recommended and for a return temperature perhaps 11C
lower. If you lower the feed temperature to an radiator then you get
less heat from it.
If you have improved the insulation or changed single glazing for double
glazing etc. then those old radiators operating at a lower output could
still provide enough heat.


*Have most CH systems in the UK been designed properly?
I've been looking at various videos on heat pumps and the conclusion
from many of the training organisations is that the level of skill in
the domestic heating industry is woefully inadequate. Not the skill in
actually performing the plumbing and fitting a boiler to a wall but more
to do with specifying the system in the first place. The problem with
this is that the many of those skills for designing the whole of a heat
pump system are also required to get the best out of a condensing boiler
system. For a heat pump to work well the rest of the system needs to be
designed for it. The same is true with a condensing gas boiler.

You can replace an old gas boiler with a modern condensing boiler and
when run at the elevated temperatures you would get the same performance
as with the old boiler, and probably with some efficiency benefits due
to better technology. To get a better efficiency other components in the
system may/will have to be changed or more spent on controlling the boiler.

[RJH]

IIRC it was Grant Shapps:

https://www.independent.co.uk/news/uk/home-news/energy-bills-cost-living-boilers-b2234246.html

The answer is/was, from memory - it might save some money, even if it doesn't
heat your home properly.

[RJH]

Yes, I tend to switch the flow temp up if it's colder. No weather compensation
here - I had it at my last place but even at its most extreme setting it was
still too cold.

> If your boiler is over specified for your central heating system, as
> seen in one recent thread in this group, setting the flow too low will
> always result in short cycling - which is far from ideal.
>

Yes, it does seem to cycle more frequently at a lower setting - not measured,
just casually observed.

> This thread started with a question about the size of the plume from two
> boilers operating with the same outside temperature. It wasn't about one
> boiler operating without a plume. What you may be seeing is normal. My
> boiler tends to produce a large plume when it's just been switched on
> and then settles to very minor plume once everything has settled down.
> Maybe you should check when your boiler is actually producing the your
> "large" plume - just after switch on? when the boiler has modulated down
> and it ticking over? when the boiler fires up again after a lockout
> period after a short cycle?

Thanks, yes, I'll take a more critical look!

[SteveW]

Mine was, because I designed and installed it myself. Over the years I
have made changes (added a conservatory with underfloor heating,
increased the boiler size to allow for the extra demand, given each room
its own timer/stat and motorised valve). I am in the process (started a
few years ago) of replacing now 30 year-old radiators with new, larger
radiators to allow for lower temperature supply from the boiler.

[Davey]

Thank you, that is the best description I have seen. In fact, it is the
only description that I have seen.

--
Davey.

[Davey]

Well, duh!
--
Davey.

[AnthonyL]

On Tue, 5 Dec 2023 11:11:45 -0000 (UTC), RJH <patch...@gmx.com>
wrote:

That recommendation is too simplistic. It relies on the boiler being
able to perform at a lower output to be effective, ie it needs to be
able to turn the burners down (modulate) to the required level.

I tried this with my 2006 Baxi boiler and it ended up short cycling,
so as soon as the radiators were warm enough it would turn off but
then shortly afterwards would have to turn back on again. Short
cycling is (as I understand it) bad for boiler life, on/off/on/off in
short order.

The problem arises because my boiler will only turn down to about 1/3
(Full power 30kW, lowest power 11kW). A more modern boiler would
modulate to about 6kW and thus run at a nice "simmer" constantly which
is good for the boiler.

The efficiency gain can be seen at:

https://www.heatgeek.com/condensing-boilers-efficiency/

https://www.urbanplumbers.co.uk/how-efficient-are-modern-condensing-boilers/

But the gains are secondary, eg 87% at 80° to 92% at 48° by which time
the boiler is temp likely to be too low to heat a house in winter.




--
AnthonyL

Why ever wait to finish a job before starting the next?

[John Rumm]

On 04/12/2023 10:53, Pamela wrote:
> The flue from my neighbour's boiler vents a large plume, while mine is
> always much smaller.
>
> All other things being equal, does this suggest my boiler is not
> condensing as mch as the neighbour's and that my boiler temperature is
> too high?

You may be reading too much into what you can "see"...

With a traditional boiler there would be a significant quantity of water
contained in the combustion gases from a normal boiler, but since they
would leave the boiler at several hundred deg C, they would be quite
well dispersed by the time they have cooled enough to form a visible plume.

A condensing boiler will condense the bulk of the water out of the
combustion gases before they even get to the flue (and in the process
recover a significant amount of heat). The flue gas temperature will
also be much cooler. So any remaining water in the combustion gas will
condense to visible water droplets sooner, and closer to the flue than
with a conventional one.

So the condenser gets a big step in efficiency from its basic design.
However there is a relationship between the return water temperature in
the main HX, and that efficiency. It improves further as it gets lower,
and shows a slight step change in the rate of improvement around 54
degrees.

There is interplay between the amount of water remaining in the flue
gas, and its temperature. Less water may give less scope for visible
plume, but lower exit temperatures means any water present may form a
visible plume closer to the flue where it will be more concentrated and
visible. So a notable difference in the amount of visible plume may not
indicate much actual change in efficiency. In much the same way a cool
damp day will also have an effect on the amount of visible plume, but
not indicate less efficiency in the boiler).





--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/

[John Rumm]

On 05/12/2023 09:58, Pamela wrote:

You have a few layers of requirement:

Flow need to be hot enough to heat the house to the desired temp
Return wants to be cool enough to boost heat recovery

However, if you engineer that temperature too low, you may force the
boiler to start cycling to hit that target flow temperature. That
actually lowers efficiency rather than increases it, and also causes
more wear and tear on the boiler.

The ideal solution is weather compensation and well designed control
systems to fine tune the operation in real time.

[alan_m]

On 05/12/2023 13:08, AnthonyL wrote:

> The problem arises because my boiler will only turn down to about 1/3
> (Full power 30kW, lowest power 11kW). A more modern boiler would
> modulate to about 6kW and thus run at a nice "simmer" constantly which
> is good for the boiler.

Not quite as simple as this. Many modern boilers may still only have a
4:1 modulation ratio so you also may also need to select a boiler with a
larger modulation and size the boiler for the CH requirements. Your
house may only have heat loss of 8KW on the coldest day and maybe 2kW on
a mild winter's day. Ideally you may select a boiler for central heating
of of perhaps 10kW. However for domestic hot water from a combi you
would need more to heat the hot water. A boiler with two different burn
settings is required. Perhaps 25KW for hot water and 10KW for CH, and
able to modulate down much further for CH.

Try this link
https://www.theheatinghub.co.uk/what-size-boiler-do-I-need

[John Rumm]

On 05/12/2023 09:37, alan_m wrote:
> On 05/12/2023 08:32, Davey wrote:
>> snip
>>
>>
>>>
>>> A year or so ago, there were a lot of suggestions about adjusting a
>>> condensing boiler setting that was said to instantly reduce the cost
>>> of running the boiler. I don't have one of these, but what was this
>>> setting, and how did it magically save money? Were there any
>>> downsides, such as loss of microbe cooking?
>>>
>>
>> Does nobody know the answer to this?
>>
>
> With a condensing boiler the manufactures default setting may have been
> a 75C flow temperature and with a resulting 60 to 65C return temperature
> from the central heating radiator system. This would mean that the
> boiler wasn't working in its condensing mode. Reducing the flow down to
> 60C would also reduce the return temperature putting the boiler into the
> condensing mode to give perhaps 3 to 4% better efficiency.

Conventional systems were typically balanced for an 11 degree drop
across the rads. Condensing system usually want a wider spread like ~20
degrees.

> In general, and for most of the central heating season, most people
> could live with a 60C flow through their radiators.

For a good proportion of the year, more than likely... in the milder
bits of the year, mine often runs flow temperatures under 50.

> The recommendation was carefully worded for the CH heating side of combi
> boilers where no domestic hot water tank is involved.

Split temperature operation sorts that, but not all boilers support it,
and not all installers seem aware of it. (probably why they like
installing combis!)

> There was/is some concern that with a hot water tank being heated by the
> boiler reducing the flow temperature to the heating coil in the tank
> wouldn't get the water hot enough (>60C) to kill legionella.  The risk
> is possibly overstated as in an occupied premises the water in the hot
> water tank is always being replenished with water from the mains dosed
> with Chlorine.  An electric immersion heater could be switched on
> perhaps once a week for a very short time to boost the boiler heated
> water to above 60C.  Some boilers may also have a inbuilt heating cycle
> to occasionally heat water in a tank to above 60C.

Yup, mine takes it to 70 one day a week.

[noth...@aolbin.com]

All this talk of balancing for a specific return temperature is fine for
a system without TRVs but I can't see (but would appreciate being
enlightened) how it can be feasible in a modern system with individual
control of room temperatures. Mechanical TRVs are an example, but a more
extreme example is the Honeywell Evohome system which fits a motorized
valve and temperature sensor on every rad. The sensors report back to a
controller which sends commands to the valves, based on the programmed
schedule for that room (without checking I think the granularity is 10
minutes and 0.5 degreesC) and sends commands to the zone valves when
there is a call for heat. I have about 20 areas running on Evohome, each
with their own schedule, several of which are set to a low temp unless
we have visitors.
How can it be possible to "balance" a system with a load that varies so
widely?

[PeterC]

My Vaillant was set to 60C flow during the frosts; it's now on 55C and will
be 50C later in the week. I control the temperatures in various rooms with
wheelhead valves and the valve where the 'stat is situated.
Due to misty weather it's difficult to use the plume so I just feel the
temperature at the flue - if it's coolish then condensing is OK>
--
Peter.
The gods will stay away
whilst religions hold sway

[alan_m]

Do you actually have 20 zones or just 20 radiators controlled by "smart"
TRVs? A programmable TRV with a schedule is fundamentally no different
to a manual TRV as far as the boiler is concerned.

The system is first designed without reference to TRVs because worst
case is with them all fully open. Balancing traditionally means that
you adjust lock shield valves so that all radiators reach the same
temperature with the TVRs open.

These days you don't necessarily have to wait for the heating to come on
and then run around like a blue arsed fly checking the temperature of
each one. The exercise can be performed on paper by those designing the
system properly.
You can get Auto Balancing TVRs
https://www.draytoncontrols.co.uk/products/radiator-valves/auto-balancing%20trvs
Also available from other manufacturers
They are not a wonder product. They just have an a range of installer
adjustments that can be set knowing the kW output, temperature drop and
flow rates through the radiator. All the parameter that should be known
when designing a heating system. Ideally after fitting the system will
be balanced without any more intervention. When fitting these you keep
the lock shield valve on the other side of the radiator fully open. They
can also be used without the TVR head for a room with a thermostat.

Modern CH pumps can operate on proportional pressure control and change
flow when TVRs or zones shut down.

Weather compensation input to the boiler's control can adjust the output
of the boiler for different outside temperatures.

[noth...@aolbin.com]

20 zones + DHW, some of the zones have a couple of rads/towel rails that
have individual motorised valves (HR92) but are logically paired and
operate together, either with one assigned to provide temperature info
or with a separate wireless room stat.
I think the fundamental difference between a full Smart system and a
dumb TRV system is that any rad can call for heat at any time (typically
it may be the only rad calling for heat at that time) whereas the
non-Smart TRV system has a room thermostat somewhere that determines the
heat call.

>
> The system is first designed without reference to TRVs because worst
> case is with them all fully open.

Yes, but surely that's just to size the boiler and pipework ...?

Balancing traditionally means that
> you adjust lock shield valves so that all radiators reach the same
> temperature with the TVRs open.
>
> These days you don't necessarily have to wait for the heating to come on
> and then run around like a blue arsed fly checking the temperature of
> each one. The exercise can be performed on paper by those designing the
> system properly.
> You can get Auto Balancing TVRs
> https://www.draytoncontrols.co.uk/products/radiator-valves/auto-balancing%20trvs
> Also available from other manufacturers
> They are not a wonder product. They just have an a range of installer
> adjustments that can be set knowing the kW output, temperature drop and
> flow rates through the radiator. All the parameter that should be known
> when designing a heating system. Ideally after fitting the system will
> be balanced without any more intervention.  When fitting these you keep
> the lock shield valve on the other side of the radiator fully open. They
> can also be used without the TVR head for a room with a thermostat.

Interesting. I hadn't hear of them but found this video:
https://www.youtube.com/watch?v=gOKcPK763XM

>
> Modern CH pumps can operate on proportional pressure control and change
> flow when TVRs or zones shut down.

Yes, mine does that but how does that help with balance?

>
> Weather compensation input to the boiler's control can adjust the output
> of the boiler for different outside temperatures.

Unfortunately my W-B boiler can't be fitted with wx compensation -
something I overlooked when spec'ing.
>
>
I've just realised that I mentioned "balance" but what I should really
have queried is how it's possible to design for a certain dT at the
boiler with a Smart system.
>

[Pamela]

On 13:08 5 Dec 2023, AnthonyL said:
>
> TRIMMED

>
> That recommendation is too simplistic. It relies on the boiler being
> able to perform at a lower output to be effective, ie it needs to be
> able to turn the burners down (modulate) to the required level.
>
> I tried this with my 2006 Baxi boiler

Last year I had a new Baxi 830 installed. Was your older model similar to
this one?

> and it ended up short cycling, so as soon as the radiators were warm
> enough it would turn off but then shortly afterwards would have to
> turn back on again. Short cycling is (as I understand it) bad for
> boiler life, on/off/on/off in short order.
>
> The problem arises because my boiler will only turn down to about 1/3
> (Full power 30kW, lowest power 11kW). A more modern boiler would
> modulate to about 6kW and thus run at a nice "simmer" constantly which
> is good for the boiler.
>

> SNIP

[Alan Lee]

On 05/12/2023 20:34, noth...@aolbin.com wrote:
>> Do you actually have 20 zones or just 20 radiators controlled by
>> "smart" TRVs? A programmable TRV with a schedule is fundamentally no
>> different to a manual TRV as far as the boiler is concerned.

> 20 zones + DHW, some of the zones have a couple of rads/towel rails that
> have individual motorised valves (HR92) but are logically paired and
> operate together, either with one assigned to provide temperature info
> or with a separate wireless room stat.
> I think the fundamental difference between a full Smart system and a
> dumb TRV system is that any rad can call for heat at any time (typically
> it may be the only rad calling for heat at that time) whereas the
> non-Smart TRV system has a room thermostat somewhere that determines the
> heat call.

That is a really poor system design. You boiler will be on and off like
a whores drawers. An open system with rads sized to their rooms is the
way forward, all controlled by weather compensation, a simple timer and
up / down temperature adjustment.
20 valves must be close to using 100 watts of electric, so you are
losing that way too, along with maintenance of that many valves, along
with the complexity of such a system.

--
Remove the '+' and replace with 'plus' to reply by email

[John Rumm]

On 05/12/2023 16:28, noth...@aolbin.com wrote:

The initial balance only really does two things - first balance the rad
outputs, but also set conditions for when the system is bring the house
up to temp. Once it is up to temp and it is just maintaining, that is
where you will need a decent modulation range to avoid short cycling
etc. It is also why you have an interlock to stop the system when the
house is satisfied.

> extreme example is the Honeywell Evohome system which fits a motorized
> valve and temperature sensor on every rad. The sensors report back to a
> controller which sends commands to the valves, based on the programmed
> schedule for that room (without checking I think the granularity is 10
> minutes and 0.5 degreesC) and sends commands to the zone valves when
> there is a call for heat. I have about 20 areas running on Evohome, each
> with their own schedule, several of which are set to a low temp unless
> we have visitors.
> How can it be possible to "balance" a system with a load that varies so
> widely?

Well the balancing bit will make sure that no rooms are not starved of
heat by other areas. The balance won't be able to maintain an overall
TDelta for the whole system once it is warm. Modulating pumps can help
there though.

[Vir Campestris]

The problem is of course how does he tell whether his plume is smaller
because
* the exhaust is too hot
* most of the moisture is condensing inside the boiler.

They would appear to have the same appearance, but opposite efficiency.

Andy

[AnthonyL]

On Tue, 05 Dec 2023 21:19:03 GMT, Pamela
<pamela.priv...@gmail.com> wrote:

>On 13:08 5 Dec 2023, AnthonyL said:
>>
>> TRIMMED
>>
>> That recommendation is too simplistic. It relies on the boiler being
>> able to perform at a lower output to be effective, ie it needs to be
>> able to turn the burners down (modulate) to the required level.
>>
>> I tried this with my 2006 Baxi boiler
>
>Last year I had a new Baxi 830 installed. Was your older model similar to
>this one?
>

There seems to be a lot of variety in the Baxi 830 range so you would
need to be more specific.

Mine is a Combi boiler (no hot water tank, just instant* hot water).

But as yours is a current model I would expect it to perform more
efficiently and have additional features.

*instant means waiting for the boiler to kick in, then waiting for the
water to get hot, then waiting for it to arrive at the tap.

[John Rumm]

Does it not have a pre-heat option? Many combis can keep a couple of
litres of water "tempered" and ready to go, so you get skip some of the
warm up time and get a response more like that from a stored water system.

[Tim+]

John Rumm <see.my.s...@nowhere.null> wrote:
> On 06/12/2023 12:06, AnthonyL wrote:
>> On Tue, 05 Dec 2023 21:19:03 GMT, Pamela
>> <pamela.priv...@gmail.com> wrote:
>>
>>> On 13:08 5 Dec 2023, AnthonyL said:
>>>>
>>>> TRIMMED
>>>>
>>>> That recommendation is too simplistic. It relies on the boiler being
>>>> able to perform at a lower output to be effective, ie it needs to be
>>>> able to turn the burners down (modulate) to the required level.
>>>>
>>>> I tried this with my 2006 Baxi boiler
>>>
>>> Last year I had a new Baxi 830 installed. Was your older model similar to
>>> this one?
>>>
>>
>> There seems to be a lot of variety in the Baxi 830 range so you would
>> need to be more specific.
>>
>> Mine is a Combi boiler (no hot water tank, just instant* hot water).
>>
>> But as yours is a current model I would expect it to perform more
>> efficiently and have additional features.
>>
>> *instant means waiting for the boiler to kick in, then waiting for the
>> water to get hot, then waiting for it to arrive at the tap.
>
> Does it not have a pre-heat option? Many combis can keep a couple of
> litres of water "tempered" and ready to go, so you get skip some of the
> warm up time and get a response more like that from a stored water system.
>

The big problem with these is that they’re often cryptically and
non-intuitively labelled (like the “Turbo” button on PCs of old). Often
just as “Eco” without any explanation of whether it should be on or off to
economise.

It’s also pretty wasteful of gas (like the old pilot lights), needlessly
keeping a reservoir of water warm at night when you don’t need instant
response.

Tim

--
Please don't feed the trolls

[RJH]

It was the cycling of my old Ideal Logic boiler that did it for me - it made
quite a bit of noise, plus the pump overrun. Also there was no reservoir -
it'd just heat the internal circuit, so of little actual benefit.

[John Rumm]

Quite often the "eco" setting turns off the hot water tempering.

> It’s also pretty wasteful of gas (like the old pilot lights), needlessly
> keeping a reservoir of water warm at night when you don’t need instant
> response.

Depends on how much it keeps and how well insulated.

[AnthonyL]

On Thu, 7 Dec 2023 16:05:02 +0000, John Rumm
<see.my.s...@nowhere.null> wrote:

>On 06/12/2023 12:06, AnthonyL wrote:
>> On Tue, 05 Dec 2023 21:19:03 GMT, Pamela
>> <pamela.priv...@gmail.com> wrote:
>>
>>> On 13:08 5 Dec 2023, AnthonyL said:
>>>>
>>>> TRIMMED
>>>>
>>>> That recommendation is too simplistic. It relies on the boiler being
>>>> able to perform at a lower output to be effective, ie it needs to be
>>>> able to turn the burners down (modulate) to the required level.
>>>>
>>>> I tried this with my 2006 Baxi boiler
>>>
>>> Last year I had a new Baxi 830 installed. Was your older model similar to
>>> this one?
>>>
>>
>> There seems to be a lot of variety in the Baxi 830 range so you would
>> need to be more specific.
>>
>> Mine is a Combi boiler (no hot water tank, just instant* hot water).
>>
>> But as yours is a current model I would expect it to perform more
>> efficiently and have additional features.
>>
>> *instant means waiting for the boiler to kick in, then waiting for the
>> water to get hot, then waiting for it to arrive at the tap.
>
>Does it not have a pre-heat option? Many combis can keep a couple of
>litres of water "tempered" and ready to go, so you get skip some of the
>warm up time and get a response more like that from a stored water system.
>

Not on my 2006 Baxi 195HE.

Under consideration for its replacement, or a small under sink
electric. Probably could get away with a solar panel on the front of
the house except regulations would say 60° required.

Water still has 20m to go from boiler to kitchen sink.