Excessive heat overnight

[Jim]

I have a combi boiler which comes on overnight and in this weather brings room temperature up to 23c. The boiler is in the garage and I am guessing its the protective function that sets it going. My radiators do not have individual temperature controls.I will in the spring do something about controls. What can I do meanwhile? Should I adjust the garage temp control or just turn off/down house rads ? Advice would be helpful. Thanks.
Jim

 

[D_Hailsham]

I have a combi boiler which comes on overnight and in this weather brings room temperature up to 23c. The boiler is in the garage and I am guessing its the protective function that sets it going.

Probably the frost protection kicking in. This usually consists of two thermostats; one measures the air temperature and turns the boiler on when it reaches 5°C, the other measures the pipe temperature and turns the boiler off when it reaches about 10°C.

This may be built in to the boiler. Which make/model boiler do you have?

Alternatively, do you have a programmable thermostat for the heating? If so, what is the overnight temperature setting, i.e the last setting?

 

[Jim]

The boiler is a Glowworm Swiftflow 100. I have a programmable thermostat and the last setting is 16c.
By the way would it help to reduce the heating temperature on the boiler itself.
Even now at 2100hrs the thermostat in the hall is showing 23c but the setting (target temp) is only 21c.
Jim

 

[Jim]

Re my last post; I have noticed that although the Honeywell programmable stat is set for 21c in the evening and its now showing 23.5c the programmable stat is not calling for heat and the "flame" sign is not illuminated. Nevertheless the boiler is actually fired up, pumping and heating.
Jim

 

[Tipper]

Probably because it's effing cold out there in your garage!

 

[D_Hailsham]

Which Honeywell prog stat are you using?

 

[mickyg]

have a look near the boiler, there's probably a frost thermostat there. will look like a room stat. Probably you have got this but not a pipe stat which is what you need to turn the boiler off again once the frost stat has kicked in. Come across this alot.

 

[Jim]

The Honeywell Programmable stat is CM907.
I took the cover off the Frost thermostat near the boiler and turned it down marginally and it switched the boiler off. Is that a dodgy thing to do?
The problem seems to be that after the frost thermostat fires the boiler it stays on.
Jim

 

[bobw1956]

. I have a programmable thermostat and the last setting is 16c.

Change this last setting to 10c should sort the problem

 

[mickyg]

I took the cover off the Frost thermostat near the boiler and turned it down marginally and it switched the boiler off. Is that a dodgy thing to do?
The problem seems to be that after the frost thermostat fires the boiler it stays on.
Jim

a pipe stat which is what you need to turn the boiler off again once the frost stat has kicked in.

 

[Jim]

Bobw1956 mentioned that I should reduce the last temperature setting(overnight) to 10c. Is this the solution if there is no pipe stat. Just curious to know how the 10c setting would fix the problem.
Thanks
Jim

 

[mickyg]

Just curious to know how the 10c setting would fix the problem.
Thanks
Jim

it wouldn't, you need a pipe stat.

 

[Agile]

Simply the frost stat in the garage might come on at say 1°C but running the boiler will not significantly alter the temperature there so the boiler stays on.

A stat on the pipe in the garage will be marginally better but the boiler will still cycle every 15 minutes or so.

Tony

 

[WDIK]

the frost stat probabley wired by a plumber.
will overide all other, programmers and stats.
bacause its in your garage, the stat will keep calling at this rate till about april, when your garage rises above 0c.

 

[Jim]

Many thanks to you all for the advice and diagnosis. I will get it looked at on the basis of your input.
Thanks
Jim