Ravenheat HE120 low nox flame cycling problem

[karlbutler1]

Can anyone help please?

I have a Ravenheat HE120 low nox boiler which has developed a problem.

On heating cycle the ingnitor kicks in OK and the flame lights. It only stays on about 15-20 secs and the system switches off. immedialtey the ingnitor kicks in again and the burners light for 20 secs again, and so on on a continuous cycle.

However, if I turn on a tap the flame lights and stays on for as long as the tap is open, however long that is, and the hot water is fine. Strangely, if the heating is on at the same time the burner then stays on OK when the tap is turned off without the fast cycling until the boiler stat finally shuts it down. Then, when the heating kicks back in it's back to the same problem again.

Hot water is fine. Heating is on fast cycle unless the hot tap has been on, which seems to override the problem, until next switch on time.

Any clues anyone ??

Regards

Karl

 

[clf-gas]

Faulty central heating thermistor.

 

[karlbutler1]

Thanks for the reply, much appreciated ! however I am a novice with limited understanding of this. where, is the thermistor, how do I replace it and is an expensive item ??

regards


Karl

 

[clf-gas]

Then if your knowledge and understanding of a boiler is limited, you require three tools.

1: A right hand with thumb and index finger present.

2:Your local yellow pages.

3: A telephone, landline or mobile the choice is yours.

Oh and one last thing money but not alot of it.
If you try repairing it you will need around £300 for an RGI to make good after you