Boiler fires up when not wanted.

[Pygmymonkey]

Can anyone help? I have a combi boiler and it will fire up all by itself when its not supposed to. The pump doesn't start (i don't think). The radiators and pipes get warm. This is despite the thermostat being switched off so it shouldn't start at all. The only way i can get it to stop is by turning on the hot tap for a short while and then when its turned off the boiler will stop.... at least for an hour or so.... I also think this only happens at night, doesn't do it in the evening and i'm not around during the day to notice (although radiators are cold when i get in from work)
Can anyone help?

 

[gas4you]

What boiler is it? A lot of new boilers are 'programmed' in the pcb to do this every 24hrs. Could this be what you are experiencing? Have you got a frost stat that is set incorrectly?

 

[namsag]

Make and model would be very helpful

 

[Pygmymonkey]

It will happen several times through the night.... not just once every 24 hours. Sorry I don't know what a frost stat is?
Its an Alpha C23 or 27....

 

[Agile]

Where is it located and does it have a seperate froststat?

Tony

 

[Pygmymonkey]

Sorry, I don't know what a frost stat is? The boiler is situated in my loft...

I've just checked a handbook i found on line and it says there is a frost stat. What is it? What does it do?

 

[Agile]

It turns the boiler on in the middle of the night when the temperature goes below 7 °C.

Tony

 

[Pygmymonkey]

Ok, thanks.....

I've just found some buff on frost stats which say the same as you, it says that the boiler will turn on at about 8°C and off when the temp is about 40°C.

That seems to make sense.... I'm trying to understand a few things though, When i turn my hot tap on for only 30 seconds, this seems to be long enough to heat it up sufficiently to turn the boiler off afterwards but when it turns itself on it does so for incredibly long periods of time and then slightly heat my radiators?

Can anyone explain why it would take so long and why, if it is on for so long, it doesn't heat my radiators alot.

 

[Agile]

It does not need to heat your rads a lot!

Its only to prevent freezing and not to heat the house.

Tony

 

[Pygmymonkey]

Excuse my ignorance... so does it come on on a low (slow) heat rather than a full burn? (ie to heat my water or properly heat my radiators)

This is the first combi boiler i've had that has done this, so i'm not really used to it... (actually it could be the first boiler i've had that hasn't been inside either the kitchen or bathroom)

Has it really been that cold outside the last few nights?

Cheers for your help!

 

[gas4you]

Most frost stats on modern boilers, not saying all of them, are 2 stage, first stage is pump just kicks in second stage boiler fires. I personally wouldn't expect current night temperatures to drop low enough to cut this in. Could be a fault in the frost stat. Is boiler still under warranty?

If Paul Barker comes on tonight perhaps he can answer more accuratley as he is the 'Alpha man'