On Sat, 10 Dec 2005 13:50:52 +0000, Bob Smith wrote:

What functions of the boiler are on the two circuit boards of my boiler
(Ravenheat RSF82E)? I know one is the control board, and the other is the
ignition board.

I have had a long term problem with the boiler stopping in it's light up
sequence just before the gas valve comes on, with 2 plumbers unable to
decide which component to replace. The gas comes on with a loud "clunk" so
I am pretty sure the solenoid is healthy, ie no half hearted / weak
operation.

Recently, this has been getting worse. It used to be that the boiler would
go for 1/2 an hour until it failed, and since there is no retry, it just
sits there blowing cold air through my heat exchanger. Recently, it is
getting so it is more often failing than working.

Another thing which has come up in the last couple of weeks is strange
on/off behaviour. It has been doing multiple clunks (2-5 times) when
lighting up, as well as seemingly ignoring the thermostat knob. There is no
click when the knob is turned, but the boiler fires up about once every
minute for about 20 seconds. It also fires up at the same rate during the
"CH timer off but pump running for a while" state, even though there is no
call for hot water. It never used to do this. All this paragraph's
problems seem to happen after it has warmed up a bit.

The boiler has never had the 3 minute lock out to stop short cycling.

The only suggestion I got from a plumber (previous to the last 2 weeks new
problems) that it may be the sensors on the inlet / outlet failing and
confusing the controller. Does this sound familiar to anyone?

Anyway, the main question is, do the above sound like there is a problem
with the controller board or the ignition board?

With this array of symptoms I wouldn't be sure there was one underlying
cause other than maybe one of the boards being marginally near failed.
However see below.

I've looked through the manual and it appears to be a fairly typical
type of combi boiler. I.e. It lights at a low rate and
detects the flame using the ignition probe and goes to a higher rate.

However It is possible that for some reason the air flow sensor is on the
blink either its inlets are dirty and/or the switch is failing.

As the boiler warms up the density of air through it drops and the
pressure due to air flow drops. This gets to the point where the APS is on
'edge' and the chattering is the gas valve dropping in/out/in/out in
response to the APS. I'd give a racing certainty that the gas valve
relay is more or less directly driven from the APS.

I'd try the following in increasing order of cost and see if you can get a
result.
1) Service the boiler.
2) Clean the inlet tubes to the APS. Check and clean the airways and
boiler in general if not done under 1.
3) Replace the APS
4) Replace the PCB.
5) Replace the ignition board.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
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