Thermostat

geoffken

Hope this this in right place.
Have 5 year old gas combi boiler normally set for 2 times a day running going off at 8.30pm which seems to run a lot during the night.
I know there is a "cold weather " thermostat which is meant to kick in when temps are low as recently but how is this determined?
Radiators are up to full temp at times during the night which seems excessive if need is only to ensure "non freezing".
Equally it appears to come on more than once.
Is this normal.

THANKS

macman

Make and model? There is normally a frost 'stat which kicks in at about 5C. If the boiler is fitted in a garage or loft then it's quite likely to trigger in recent weather. Is it?
Most unlikely that your internal house temp will drop that low though.
Possible faulty timer or frost 'stat sensor?

geoffken

Thanks for reply.

Model is Gloworm 30cx1(i?)

Is in cupboard in hall i.e. in middle of house so not likely to be affected by external temp.
Bungalow is 2 bedroom well insulated and cavity insulated and double glazed so not likely to have major heat loss overnight.
Should radiators heat to normal temp or just enough to get hot water through them?

Thanks

rogerblack

geoffken wrote: »

Should radiators heat to normal temp or just enough to get hot water through them?

When the frost stat goes off, the radiators likely will heat to normal temperature, and keep on, until the frost stat switches off.
However, this should only be at very low temperatures - to maintain the temperature at perhaps 5C.

If you have very low temperatures, then yes, this is normal.
If the temperature is not going this low, then there is a fault with the thermostat, or it is designed for too high a 'frost' temperature.
For example - if set to 10C, it would in most cases use a vast excess of gas over what is required to keep the pipework from freezing.

Fire_Fox

Possibly faulty timer or thermostat.

geoffken

Thanks again.
You are all confirming my suspicions but as service engineer dismissed my concerns and another plumber/gas engineer stated the same I was beginning to doubt my interpretation of frost stat.
A further query is heating comes on during day for short periods(obviously not drawing hot water) but as temp during day today is normal for time of year is this normal?
Sorry if you are having to drag info out of me.

macman

You need to log the time and temp at which it kicks in overnight. Is there any pattern?
For example, if it always comes on at 3.29am each nght, it's clearly a timer fault.
Is it an integral or separate 'stat/programmer?

rogerblack

And what temperature is it at the stat/boiler when this occurs.

gas4you

Your boiler has a two stage frost protection built in.

At 7c it will start the pump only to circulate the water, as running water is less likely to freeze.

When it drops to 3c the boiler will fire up to heat itself and then should switch off at 10c.

You seem to have a fault somewhere.

Possibly a faulty ntc.

Do you find the radiators get warm/hot when running a hot tap?

If so the diverter valve could be stuck mid position and when the DHW pre-heat cuts in (assuming you have it switched on) the rads will get hot as you describe.