It's a Ravenheat RSF82E. It's a fanned combi, the kind that lights every time there is a demand for heat (ie no pilot). I have a manual / website for the manual if that would help.
About 1 in 50 times, it fails to light when the CH water cools off a bit. It is part way through the lighting cycle that it fails, the big "clunk" that the gas valve makes. I am not sure what is causing it though, and have
3 theories.1) The gas valve is sticky (although I hear no failed mini "clunk") and fails 1 in 50 times.
2) The fan is faulty, and does not draw enough air for the boiler to think it is safe to light (assuming the boiler is that smart). The fan does sound scraping / rattly when it slows down. A gust of wind could shift a borderline fan to a "not fast enough" state.3) The sensor that detects the fan is working is faulty / blocked with fluff (assuming it is that smart).
Is there anything else that could cause this? Any quick and cheap (eg tap gas valve with hammer, hoover sensor out) fixes that cure common problems?
The boiler would work fine if it had a "retry" built into the lightup sequence, but as it is, I keep finding the boiler with a light lit up, merrily blowing cold air past the CH water (the fan comes on before the gas) chilling it. Turning the thermostat down then up, or switching CH off then on restarts the lightup sequence. The proper "reset" botton does nothing (not lack of flow/boiling water problem).
Extra info/hint: Sometimes if I am there when it fails to light, me doing the the on/off thing causes it to try again, but it will fail to light 2 or
3 times in a row, suggesting it is some condition causing the failure that goes within 30 seconds.Any ideas / suggestions?
Thanks
Bob