Your opinion on CH Boiler setting


J

Justine Time

Googling brings up different opinions.

I have a Worcester Bosch Condensing boiler and probably like most
boilers it has a boiler temperature control.If I have the room
thermostat and tvr's on the rads would I put the setting on the bolier
(and leave it ) on max. I have read that this would waste gas but, also
read the opposite, surely it would heat the room up quicker and
therefore shut off the boiler sooner than later, the temp of the rooms
governed by the room thermostat/tvr's. Have also read having it on max
would (could) have the returning temp above 45 degrees and the boiler
would not condense efficiently. I have read definitely not to definitely yes
What is your opinion, they seem to vary from what I have looked up as to
the best setting.
 
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M

Martin Brown

Googling brings up different opinions.

I have a Worcester Bosch Condensing boiler and probably like most
boilers it has a boiler temperature control.If I have the room
thermostat and tvr's on the rads would I put the setting on the bolier
(and leave it ) on max. I have read that this would waste gas but, also
read the opposite, surely it would heat the room up quicker and
therefore shut off the boiler sooner than later, the temp of the rooms
governed by the room thermostat/tvr's. Have also read having it on max
would (could) have the returning temp above 45 degrees and the boiler
would not condense efficiently. I have read definitely not to definitely
yes
What is your opinion, they seem to vary from what I have looked up as to
the best setting.
Entropy essentially determines that all other things being equal running
the boiler at a setting where it provides just enough heat to the
heating system will be more efficient. It costs slightly more to deliver
extra heat to already hot water from the boiler flame.

But don't take my word for it - do the experiment and monitor your gas
consumption and min/max external temperatures. Nothing beats experiment!

You may have to wind the wick up a bit in cold weather if you set the
boiler thermostat for optimum fuel efficiency.
 
F

fred

Justine Time said:
Googling brings up different opinions.

I have a Worcester Bosch Condensing boiler and probably like most
boilers it has a boiler temperature control.If I have the room
thermostat and tvr's on the rads would I put the setting on the bolier
(and leave it ) on max. I have read that this would waste gas but, also
read the opposite, surely it would heat the room up quicker and
therefore shut off the boiler sooner than later, the temp of the rooms
governed by the room thermostat/tvr's. Have also read having it on max
would (could) have the returning temp above 45 degrees and the boiler
would not condense efficiently. I have read definitely not to definitely yes
What is your opinion, they seem to vary from what I have looked up as to
the best setting.
My approach is to set the boiler stat to the lowest level that can
maintain an acceptable comfort level and gave a reasonably short warmup
time. In general this gives a long slow burn which in my view gives more
efficient running and a better comfort level.

Compare the highest setting with driving balls out between sets of
traffic lights then sitting idling at the next red and a middle setting
with moving at a more leisurely pace and (hopefully) arriving at the
next light just as it changes to green.

In practice, mine is never set below half, is currently set just over
half but it may be set at 3/4 or higher in the depths of winter.
 
G

gremlin_95

Googling brings up different opinions.

I have a Worcester Bosch Condensing boiler and probably like most
boilers it has a boiler temperature control.If I have the room
thermostat and tvr's on the rads would I put the setting on the bolier
(and leave it ) on max. I have read that this would waste gas but,
also read the opposite, surely it would heat the room up quicker and
therefore shut off the boiler sooner than later, the temp of the rooms
governed by the room thermostat/tvr's. Have also read having it on max
would (could) have the returning temp above 45 degrees and the boiler
would not condense efficiently. I have read definitely not to
definitely yes
What is your opinion, they seem to vary from what I have looked up as
to the best setting.
As low as possible really to heat your house, it would need tweaking now
and then in very cold weather. I have a Vaillant Ecotec and recently
upgraded to weather compensation which does all the work for me :)
 
G

gremlin_95

As low as possible really to heat your house, it would need tweaking
now and then in very cold weather. I have a Vaillant Ecotec and
recently upgraded to weather compensation which does all the work for
me :)
By the way, OP is your boiler a combi boiler or do you have an indirect
cylinder heated by the boiler?
 
N

NT

Googling brings up different opinions.
I have a Worcester Bosch Condensing boiler and probably like most
boilers it has a boiler temperature control.If I have the room
thermostat and tvr's on the rads would I put the setting on the bolier
(and leave it ) on max. I have read that this would waste gas but, also
read the opposite, surely it would heat the room up quicker and
therefore shut off the boiler sooner than later, the temp of the rooms
governed by the room thermostat/tvr's. Have also read having it on max
would (could) have the returning temp above 45 degrees and the boiler
would not condense efficiently. I have read definitely not to definitely
yes
What is your opinion, they seem to vary from what I have looked up as to
the best setting.
The most efficient will be "just hot enough to get the house to its
target temperature"[3].

There are several factors at work here:

First boiler performance, lower return temperatures promote more
condensing efficiency. Lower flow temperatures result is smaller
overshoots when reaching the set temperature. Longer burns result in
less efficiency loss from boiler cycling (although this is much smaller
on a modern boiler than an old one). It also means slower warm ups
(which is a trade off), but a slower warm up means a lower overall
average temperature[1] - and the lower the temperature, the lower the
rate of heat loss from the building generally[2].

[1] If the heating runs five hours maintaining a target temp of say 20
degrees but takes 1 hour to reach it the average temperature is slightly
lower than with a system that reaches target in 20 mins.

[2] Unless taken to an extreme - if cold enough that the walls get damp,
then they will lose heat faster than if kept dry.

[3] This after all is what weather compensators attempt to do.
Just one thing not mentioned yet: max HW cylinder temp is limited by
the temp in the primary circuit. So if yuor boiler stat setting is to
low, the HW wont be hot enough.

In short, the most energy efficient option is to set the boiler stat
low at this time of year, and turn it up when it gets really cold, and
the pump's running a lot of the time to try to keep the house warm.


NT
 
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S

Scott M

fred said:
Compare the highest setting with driving balls out between sets of
traffic lights then sitting idling at the next red and a middle setting
with moving at a more leisurely pace and (hopefully) arriving at the
next light just as it changes to green.
Excepting that, instead of idling at the red light, the boiler will turn
the engine (pilot light) off.
 
G

gremlin_95

Yes it is a combi
Good, you can get away with setting the flow temperature quite low. With
a conventional boiler with standard controls (i.e. ones which cannot
adjust the flow temperature automatically) you wouldn't be able to get
away with much lower than around 65ºc because the water wouldn't get hot.
 
R

Ret.

Googling brings up different opinions.

I have a Worcester Bosch Condensing boiler and probably like most
boilers it has a boiler temperature control.If I have the room
thermostat and tvr's on the rads would I put the setting on the bolier
(and leave it ) on max. I have read that this would waste gas but, also
read the opposite, surely it would heat the room up quicker and
therefore shut off the boiler sooner than later, the temp of the rooms
governed by the room thermostat/tvr's. Have also read having it on max
would (could) have the returning temp above 45 degrees and the boiler
would not condense efficiently. I have read definitely not to definitely
yes
What is your opinion, they seem to vary from what I have looked up as to
the best setting.
I emailed WB tech support on this very issue. This is the reply they sent:

Thank you for your enquiry.

Whilst using your room thermostat it is important to obtain the most
efficient flow and return temperatures to extract the highest output
from the boiler with the lowest temperature of flow. Please see diagram
below from installation instructions:

Central Heating:
Max. rated heat input kW 30.9
Max. rated heat output net 40/30 deg C kW 32.1
Max. rated heat output net 50/30 deg C kW 31.8
Max. rated heat output net 80/60 deg C kW 30.0

From 1 to MAX on your CH control knob on the boiler work in 8°C
increments starting from 35°C-88°C MAX.

This table shows of the higher kW gains achieved by reducing flow
temperature and achieving a more balanced return. Certainly having the
boiler short cycling at full output will reduce the economy so by
setting your CH control knob to a lower temperature over a longer demand
period will improve the efficiency. It may take slightly longer to heat
the property but once heating the boiler will be producing more
efficient flow/return temperatures therefore increasing the condensing
process making the demand more efficient.

We hope this answers your query satisfactorily.

Kind regards

Technical Support
Worcester, Bosch Group

--
Kev

Justice? You get justice in the next world,
in this world you have the law...
William Gaddis
 
J

Justine Time

I emailed WB tech support on this very issue. This is the reply they sent:

Thank you for your enquiry.

Whilst using your room thermostat it is important to obtain the most
efficient flow and return temperatures to extract the highest output
from the boiler with the lowest temperature of flow. Please see diagram
below from installation instructions:

Central Heating:
Max. rated heat input kW 30.9
Max. rated heat output net 40/30 deg C kW 32.1
Max. rated heat output net 50/30 deg C kW 31.8
Max. rated heat output net 80/60 deg C kW 30.0

From 1 to MAX on your CH control knob on the boiler work in 8°C
increments starting from 35°C-88°C MAX.


Worcester, Bosch Group
Interesting.... I can work on that.
thanks
 
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J

Jonathan

Good, you can get away with setting the flow temperature quite low. With
a conventional boiler with standard controls (i.e. ones which cannot
adjust the flow temperature automatically) you wouldn't be able to get
away with much lower than around 65ºc because the water wouldn't get hot.
What is low roughly - do you mean 40C say? I am interpreting you as
saying with a condensing boiler I can have water at 55C and heating at
40C and still have hot water.

Jonathan
 
G

gremlin_95

What is low roughly - do you mean 40C say? I am interpreting you as
saying with a condensing boiler I can have water at 55C and heating at
40C and still have hot water.

Jonathan
Basically with a regular condensing boiler (where you have a separate
cylinder heated by the boiler and an immersion heater for back up), to
get the water in the cylinder hot you would need to have the boiler stat
set approximately 10ºc higher than the ideal cylinder temperature which
is 55ºc and above to stop legionella, hence mentioning 65ºc as a minimum
flow temperature if you don't have a combination boiler or more complex
controls. You can't heat water in the cylinder to 55ºc if you have the
flow temperature at just 40ºc.

If you had a condensing combi then you wouldn't need to worry about the
water in the cylinder.
 
C

cynic

I emailed WB tech support on this very issue. This is the reply they sent:

Thank you for your enquiry.

Whilst using your room thermostat it is important to obtain the most
efficient flow and return temperatures to extract the highest output
from the boiler with the lowest temperature of flow. Please see diagram
below from installation instructions:

Central Heating:
Max. rated heat input kW 30.9
Max. rated heat output net 40/30 deg C kW 32.1
Max. rated heat output net 50/30 deg C kW 31.8
Max. rated heat output net 80/60 deg C kW 30.0

 From 1 to MAX on your CH control knob on the boiler work in 8°C
increments starting from 35°C-88°C MAX.

This table shows of the higher kW gains achieved by reducing flow
temperature and achieving a more balanced return. Certainly having the
boiler short cycling at full output will reduce the economy so by
setting your CH control knob to a lower temperature over a longer demand
period will improve the efficiency. It may take slightly longer to heat
the property but once heating the boiler will be producing more
efficient flow/return temperatures therefore increasing the condensing
process making the demand more efficient.

We hope this answers your query satisfactorily.

Kind regards

Technical Support
Worcester, Bosch Group

--
Kev

Justice? You get justice in the next world,
in this world you have the law...
William Gaddis
The logical next step is to incorporate into the boiler pcb a simple
controller which will start from a cold house at maximum boiler output
temperature then progressively reduce this as the desired set point
for room temperature is approached. This would provide for a later
start, rapid warm up, and maximum combustion efficiency once warm.
Predictive switching on and off depending on exterior conditions can
also be employed, together with self-learning. All this has been
around in commercial systems for years.
 
G

gremlin_95

The logical next step is to incorporate into the boiler pcb a simple
controller which will start from a cold house at maximum boiler output
temperature then progressively reduce this as the desired set point
for room temperature is approached. This would provide for a later
start, rapid warm up, and maximum combustion efficiency once warm.
Predictive switching on and off depending on exterior conditions can
also be employed, together with self-learning. All this has been
around in commercial systems for years.
Indeed, my Vaillant VRC430f does all of this. It can even be mild
outside but if the temperature has dropped really low inside the house
(normally happens when the house is ventilated by leaving windows and
doors open for a while) the device will request quite a high flow
temperature and reduce it as the room approaches the target temperature.
 
F

fred

gremlin_95 said:
Basically with a regular condensing boiler (where you have a separate
cylinder heated by the boiler and an immersion heater for back up), to
get the water in the cylinder hot you would need to have the boiler stat
set approximately 10ºc higher than the ideal cylinder temperature which
is 55ºc and above to stop legionella, hence mentioning 65ºc as a minimum
flow temperature if you don't have a combination boiler or more complex
controls. You can't heat water in the cylinder to 55ºc if you have the
flow temperature at just 40ºc.
I think some boilers have dual settings, one for CH demand and one for
HW demand. My boiler didn't have this feature so I modified it with a
relay and a few components to make it run flat out when on HW demand and
this works well but would have obvious implications for warranty cover.
 
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G

gremlin_95

gremlin_95 said:
I think some boilers have dual settings, one for CH demand and one for
HW demand. My boiler didn't have this feature so I modified it with a
relay and a few components to make it run flat out when on HW demand
and this works well but would have obvious implications for warranty
cover.
Yes you do get some with dual settings, most of the time it involves
using the boiler manufacturers accessories/controls
 
M

Mark

The logical next step is to incorporate into the boiler pcb a simple
controller which will start from a cold house at maximum boiler output
temperature then progressively reduce this as the desired set point
for room temperature is approached.
That's called modulating. Most modern boilers do this AFAIK.
--
(\__/) M.
(='.'=) Due to the amount of spam posted via googlegroups and
(")_(") their inaction to the problem. I am blocking some articles
posted from there. If you wish your postings to be seen by
everyone you will need use a different method of posting.
 
R

Ret.

Yes you do get some with dual settings, most of the time it involves
using the boiler manufacturers accessories/controls
My WB combi (Greenstar CDi 30) has separate controls for heating and hot
water temperature. It also 'condenses' on hot water use which,
apparently, many combis do not.

--
Kev

Justice? You get justice in the next world,
in this world you have the law...
William Gaddis
 
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