Ravenheat Problem

[Agile]

In that case, as I cannot think of anything else, I would expect the fan PCB will be the culprit as I said at first.

Dont blame me if its not ! I have been no where near your boiler.

Tony

 

[GodKnows]

As Tony and Slug states fan pcb, but, I would check the CH sensor as well, get your multimeter and check the ohms across the terminals. Don't want you to fork out for a pcb fella if a cheap CH sensor is at fault
After all, if it works on DHW, then something on the CH side is amiss... As Slug stated at the beginning

 

[Malcolm5432]

I'm getting about 6.7 kOhms at 36.0 degrees C (armpit) 12.6 kOhms at 17.0 degrees C and 16.0 kOhms at 6.0 degrees C. This all seems to be about correct from advice that you gents have given to previous questioners, let me know if I'm wrong. I'm probably going to go for replacing the fan PCB. Thanks and I'll let you know the outcome.

 

[Slugbabydotcom]

I'm getting about 6.7 kOhms at 36.0 degrees C (armpit) 12.6 kOhms at 17.0 degrees C and 16.0 kOhms at 6.0 degrees C.

Thats near enough in my book. Hopefully it isnt out of sync at higher temperatures. Its a faff on to concoct a test rig and few people will bother with that which is why I carry a spare one with me to test
As I recall the range is 20k at Close to 0ºC and 500 Ohm @ about 85ºC

 

[gigz]

Have you tried phoning ravenheats tech helpline, never phoned for a while but they used to be very good.

 

[Oldmanfrank]

As stated obviously a problem with fan be it one way or another. I would say fan speed not allowing boiler to modulate correctly, check venturi for dirt or blockages.

 

[Slugbabydotcom]

Would you christmas eve it! I made that post earlier then went out to sort a few boilers out. 5pm got a call to a local job courtesy of Ravenheat. Identical problem.

The boiler operates fine coming on and off ok but continually cycles. it will come on for 1 second at hi flame then drop to low for a second and cut out completley. this process complestes over about 3 seconds and hapeens continually when in ch mode dhw is not affected.

At the time the flame dropped to low I could hear than fan slow down.
Fitted a new fan mod board and at the same point the fan stayed at high speed and the flame didn't cut out.
I did of course check the thermistor first but knew it would probably be ok as it was the clip on type.

 

[GodKnows]

That's scary and coincidental Slug Will remember that one cheers...

 

[Malcolm5432]

A new fan mod PCB fixed mine as well. Thanks for all your help, it is very much appreciated. I'll probably be back with the next problem but not too soon I hope!

Malcolm