Hi all,

Could anyone with a better understanding of the psychology of boilers
than me give an opinion on this.

The boiler is a Baxi Bermuda back boiler. It's about four years old.
It has had an ongoing problem with printed circuit boards - they
"blow" from time to time.

The most recent PCB failure resulted in me sending the blown one to
Geoff on here. He replaced a transistor on it - his opinion was that
the gas valve must be faulty and drawing too much current, because the
failed transistor was controlling the gas valve. We put the
reconditioned PCB in and simultaneously replaced the gas valve.
However the PCB still produced a lock-out. We adjusted the gas
pressure on the new gas valve up and down to no avail.

In frustration we put the old gas valve back in. With the old gas
valve, the now reconditioned PCB (and with everything demanding heat)
the boiler now fires up, but only for about five seconds. The burners
then all go off for a few minutes before coming on again for a few
seconds, etc etc. Would this be a flame sensor problem?

What seems odd is
(a) that the flame sensor and the PCB failure should coincide, and
more strangely
(b) why does the old gas valve produce some sort of response whereas
the new one produces complete PCB lockout.

Any ideas very gratefully received, at the moment we're slowly
replacing the boiler part by expensive part and getting nowhere.

(By the way, the "we" is because my brother is doing the hard work
with me chipping in by phone).

Martin

In message
,
Martin Pentreath writes
Hi all,

Could anyone with a better understanding of the psychology of boilers
than me give an opinion on this.

The boiler is a Baxi Bermuda back boiler. It's about four years old.
It has had an ongoing problem with printed circuit boards - they
"blow" from time to time.

The most recent PCB failure resulted in me sending the blown one to
Geoff on here. He replaced a transistor on it - his opinion was that
the gas valve must be faulty and drawing too much current, because the
failed transistor was controlling the gas valve. We put the
reconditioned PCB in and simultaneously replaced the gas valve.
However the PCB still produced a lock-out. We adjusted the gas
pressure on the new gas valve up and down to no avail.

In frustration we put the old gas valve back in. With the old gas
valve, the now reconditioned PCB (and with everything demanding heat)
the boiler now fires up, but only for about five seconds. The burners
then all go off for a few minutes before coming on again for a few
seconds, etc etc. Would this be a flame sensor problem?

What seems odd is
(a) that the flame sensor and the PCB failure should coincide, and
more strangely
(b) why does the old gas valve produce some sort of response whereas
the new one produces complete PCB lockout.


This is a bit weird

I've forwarded the post to Max to see what he says

--
geoff

On 04/12/2011 16:34, Martin Pentreath wrote:

In frustration we put the old gas valve back in. With the old gas
valve, the now reconditioned PCB (and with everything demanding heat)
the boiler now fires up, but only for about five seconds. The burners
then all go off for a few minutes before coming on again for a few
seconds, etc etc. Would this be a flame sensor problem?


Had something similar to this on a friends Ideal Mexico RS last year.
Seemed to be a failure of the gas valve in that it would light the main
burner and run for a few mins, but then shut off before the system
really had a chance to get hot. The clue was that even when the burner
shut off, there was still 240V on the input to it, so it was definitely
a valve fault.

--
Cheers,

John.

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