Hi I am a house owner in Wales.

[paul b]

I have a ideal 24 combi in attic. last year during very cold nights the frost stat would kick in and heat the whole house , just because the attic was cold. i had a pipe stst fitted a week or two back by a plumber and every day / night since the CH is coming on / going off. so the pipe stat is working but was is turning the CH on in this mild weather ?

 

[UNG]

What is the expected function of the pipe stat?

I'm assuming the frost stat is built into the boiler and operates at a temperature preset by the manufacturer

 

[paul b]

What is the expected function of the pipe stat?

I'm assuming the frost stat is built into the boiler and operates at a temperature preset by the manufacturer

hi. the frost stat came with boiler set at 5. the pipe stat is needed to turn the CH off in winter months when the frost stat has turned it on. cos the attic is much colder than the house

 

[UNG]

hi. the frost stat came with boiler set at 5. the pipe stat is needed to turn the CH off in winter months when the frost stat has turned it on. cos the attic is much colder than the house

So you would risk the boiler freezing and damaging the heat exchanger which would be costly to replace because you are too warm

Without digging into the boiler wiring diagram to verify you might have been better getting a smart thermostat or heating controller that could limit the overnight heating temperature to 8 - 10°C

 

[paul b]

So you would risk the boiler freezing and damaging the heat exchanger which would be costly to replace because you are too warm

Without digging into the boiler wiring diagram to verify you might have been better getting a smart thermostat or heating controller that could limit the overnight heating temperature to 8 - 10°C

what i have said is the CH is constantly coming on NOW when weather is mild (15’) in attic with frost stat set at 5’ so asking what is turning my CH on ?! i am not risking the boiler freezing

 

[brianmoooore]

Pipe 'stat and frost 'stat should both be fitted, and connected in series. Pipe stat should be on the return boiler pipe and set at about 5 degrees. There will be some heating of the house, but it should be minimal with the return flow limited to just above freezing.

 

[UNG]

what i have said is the CH is constantly coming on NOW when weather is mild (15’) in attic with frost stat set at 5’ so asking what is turning my CH on ?! i am not risking the boiler freezing

How are you measuring / monitoring the overnight temperature in the loft is the 15°C an actual measured temperature

 

[paul b]

How are you measuring / monitoring the overnight temperature in the loft is the 15°C an actual measured temperature

actual

 

[brianmoooore]

The frost stat needs to be fairly close to the boiler, so that it is affected by the heat leaking from the boiler.
The odd bit of panelling near the boiler might help. Not to enclose the boiler, but to protect it from draughts in the attic.

 

[brianmoooore]

Three of my boilers are fitted with frost protection. Two are in fairly small outdoor sheds, which become a few degrees above the ambient when the boiler is running, and the third is a standalone outdoor unit, where the frost 'stat is actually inside the boiler casing.
All three prevent the boiler and external pipework from freezing with minimal heating of the property.

 

[brianmoooore]

If the temperature in the attic is really 15 degrees, then it sounds like you need a more accurate frost 'stat with limited hysteresis.

 

[Avo Mk8]

Maybe the plumber wired the pipe stat in parallel with the frost stat instead of in series, and it's also set at too high a temperature!!

 

[James]

If the pipe stat is working correctly and set a 5 or 10 degrees, the radiators should not be getting hot.
pit takes a while for the stat to recognise that it is warming up but I would not expect the flow temp to go much above 20 before the boiler turns back off again.

 

[paul b]

If the temperature in the attic is really 15 degrees, then it sounds like you need a more accurate frost 'stat with limited hysteresis.

hysteresis ?

 

[brianmoooore]

Difference between the temperature in switches on at when the room temp is falling, and the temp it switches off again when the temp rises.