Alpha 240p pilot outage

[wendiff]

Hi everyone,


My boiler, which has worked fantastically for the last 2 years thanks to your help on previous problems, has developed a problem for which I cannot find an answer to in the faqs.

DHW works fine, a bit too hot if anything, but CH fires up only for 30-40 seconds makes a slight wooshing noise and cuts out only to fire up again several minutes later (3-5 minutes). As long as the pilot hasn't cut out the cycle is repeated and over time the rads do heat up although not as hot as before and one is less hot at the bottom than top. The big trouble is that the pilot often cuts out sometimes very quickly although sometimes it lasts a day or more.

In the last 3 years I have fitted a new heat exchanger, diverter manifold/valve, and auto air vent and it was running fine till this artic freeze.

My logic tells me it is overheating but it doesn't dump water, doesn't leak anywhere and the pressure remains fairly constant (expansion vessel is at bar. I have drained and refilled it, checked pump function, fan, everything, I can think of. Any ideas what it could be and what repair I am looking at?

Wendi

 

[nickso]

your description would point to a stuck diverter or blockage in the heating circuit. how old is the diverter you put on?

 

[wendiff]

Hi Nickso, thanks for the reply.


The diverter valve was replaced in June 2007. The heat exchanger in 2008 and the auto air vent just 2 weeks ago. The first two parts brand new from Ezyparts.

Wendi

 

[nicknox]

Check that the filter in the return valve (under the boiler) is not blocked. This would cause very poor ch and overheating (pilot outage) as a result.

 

[wendiff]

Important update to my problem.

My pilot won't stay alight at all now !!! It just goes out as soon as I release the button so no DHW or CH - ???

Please any ideas someone - could it be the thermocouple needs replacing and is that a Corgi job?

Wendi

 

[gas4you]

Could be the thermocouple.

Is the fan spinning fast when you depress the button on the gas valve to light the pilot?

It should spin fast until the pilot lights then drop back to slow speed.

 

[wendiff]

Hi gas4you - had your help a year ago so thanks again.

Fan spins faster when depressed. Pilot lights ok, I think normal size flame, until I let go after the around 60 seconds.

Monday we completely checked and overhauled everything as posted and system was working ok till this morning when I turned heating up. Shortly after that pilot went out but this time different to others I just can't light it again.

Wendi

 

[wendiff]

NEW DEVELOPMENT

Just tried to light the pilot again as am getting a bit cold. Now after 2-3 hours cold and gently cleaning tip, the pilot light has stayed on. First tested DHW - was ok - but when I turn on CH it is still only firing up for seconds then off several minutes , then on again for seconds, then off again, etc. etc. etc.

Don't know how long pilot will stay lit but I'm not holding my breath!

Looked in manual - could overheat thermo need replacing as well as thermocouple - or a new gas valve ???

 

[gas4you]

Personally I would replace the ch thermistor and the thermocouple.

If it was overheating you would get the warning light on the front of the boiler.

Your boiler is 'faulting' without the boiler actually knowing it.

 

[Gasguru]

This is the pilot version...no warning light, it just cuts the pilot.

As said before check the return filter..it's located inside the return isolating valve. Remove the large hex fitting on front of the valve. Often these boilers are not range rated and the boiler trips the overheat stat before it can modulate down due to linited flow through the bypass.

As for the current pilot problems....once the overheat stat has opened the contacts often wont close with sufficiently low contact resistance due to oxidation ie. it may require replacement.

Since you have have the combustion cover and front insulation panel off you need to be very careful on replacement. Were all the spire clips (all 5) in good condition? Were all 5 screws in place? Did the 2 lugs on the front cover fully locate in the burner rail. If any clips are broken/screws missing or the lugs aren't located the burner slots the boiler can produce significant quantities of carbon monoxide since fan airflow bypasses the burner.

Corgi only territory really.

When re-lighting the pilot, as soon as the pilot has ignited turn the boiler off to stop the fan. This will allow the flame to envelope the thermocouple better. Once the valve holds in switch back on.

 

[nicknox]

Still pointing to a restriction/blockage in the ch sytem and still likely to be the return filter. The ch or primary sensor operates for both ch and hw so unlikely to be that as combi boilers are more likely to overheat on hot water rather than ch and it works on hw.

 

[wendiff]

Thanks all - I'm working on the suggestions and will be back once any results.

I've located the return isolating valve but am loathe to touch it unless the pilot goes out again (it's been live since yesterday so I'm quite warm at the moment!) and also because spanners are more suited to my stronger handy fella who can't come over until Monday. We will most likely replace the Overheat Stat then too and see if the thermocouple needs replacing also and CH thermo.



Thanks for the concerns Gasguru. I was very very careful - no spires or screws either broken, corroded or missing (none left over either!) and both plaques slotted neatly back into position as if never moved. I am fortunately, at least for this kind of thing, horribly finicky!

Wendi

 

[wendiff]

GOOD NEWS!

As everyone suggested it appears it was the return valve which was like a coal mine inside. After a trip to Spare Parts to find a new one cost £57.00 and they had none in stock anyway a few more wrenches gave access to the inside mesh which I have cleaned back to a shine. Now CH gets hot evenly and rapidly with boiler staying on several minutes at a time as before and running quiet as a mouse.

So fingers crossed I can leave replacing thermistor, thermocuple or overheat stat till the next problem otherwise I will run out of parts to replace!

Thanks, thanks and thanks again to all of you as a really fantastic and helpful set of pros.

Wendi