I have a Ravenheat CSI 85at that is just over 3 years old. This is the one that does NOT have the honeywell gas valve and red ignition PCB or pilot light.
The problem is that the boiler on CH demand starts up then after about 5 seconds the fan turns off and the boiler closes down. Ten seconds later the boiler starts up and goes through the cycle again then closes down. This goes on and on and on. However if I run the hot water for 20 secs, once the hot water has been turned off the boiler works fine supplying heat to the CH system until it needs to fire up again due to timer swithing off or reaching thermostate level. Each morning I have to get up when the timer switches the boiler on to run the hot water for 20 secs so that the house will heat up.
After reading all of the comments on this excellent web site, I think the Green ignition PCB needs changing to resolve this problem? Does anybody know for sure so that I dont spend £70 unnecessarialy?
Thanks

Neil, February 2010

If the pcb board is faulty, the boiler won't fire up at all either for heating or hotwater, so save yourself the cost of purchasing one and being disappointed.The most common cause of this problem is the overheat cut off thermostat, usually found on the upper right hand side of the boiler (check the manual). The system will need to be drained, then the replacement takes seconds.

Peter, February 2011

Mine did that. Its a hot water thermistor in the primary heat exchanger on the right hand side of the unit half way up. It costs about £20 to replace the switch if your competent enough to do yourself.

Dave G, February 2010

Neil. I'm sorry, I can't answer your question but I wanted to thank you very much for your tip. My Ravenheat boiler does exactly the same - it keeps firing up every 20 seconds but then, by magic, this seems to stop after a while. It started again this afternoon and I've just been to run the hot - and it's stopped (not magic after all!). Thank you very much for a help. We just need someone to answer your question properly now to see if your suggestion about changing the PCB is right.

Angela, February 2010