Combi boiler not firing up

Hi, I have a Chaffoteaux et Maury Brittony Combi 80 boiler.

The central heating was working fine but during the past week the domestic hot water suddenly started running cold. Then it came through hot again. Now it's running cold again.

I pulled out the main heat exchanger, wondering if there might be a blockage in there. There wasn't. I put it back.

My local plumbing shop said it was probably the 3-way diverter valve that wasn't working. I found that valve and removed the brass thing that plugs into the top with a watertight o-ring seal. I cleaned up the dirty end, thinking that the fault might be due to a bad electrical contact there. (I wasn;t sure how the thing works, but thought there may be a plunger inside that rises to touch the brass thing when the water pressure rises. I replaced it after cleaning.

I opened up the cold water inlet again and switched the boiler on. Now it doesn't fire up at all! Not even for the central heating. The fan comes on, but no flame. Anyone help me with a diagnosis?

Thank you

Dave£

Reply to
Dave£
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PS, Yes, I did restore the water pressure to 2bar. I can't hear any sparking going on when I try to fire it up.

Reply to
Dave£

PPS... Yes, I did try pressing the reset button s few times, but it still doesn't fire up.

Reply to
Dave£

PPPS.. AFter leaving the thing alone for a few hours, I decided to remove the cover of the flame compartment. Tried again, and this time it fired up! So I put the cover back on, switched the boiler off thn on again. This time it fired up for a few seconds and went out again. I tried one more time; this time it fired up, kept burning, but the gas seems to be coming through in pulses (about four pulses per second). Or, at least, the flame is pulsating. Strange! I've never heard that effect before. Anyon know what the cause might be?

At least the c/h and the dhw is heating up properly at the moment. Though I think I detect a reduction of the hot water pressure at the domestic taps.

Thanks

Reply to
Jim T

PPPPS.. The flame is now smooth (no pulsation). That's after leaving the boiler running for 20 minutes or so. Anyone know what was going on?

Cheers, Dave

Reply to
Dave£

There are a range of syptoms which seem unrelated to each other. Removing the combustion chamber cover can make some boilers start working well until it is replace. (And vice versa - especilly those that need the cover on to operate!).

If I were coming cold to a boiler with a set of (apparently) unrelated symptoms. The first thing I would do is to check that every thing than can be measured is right. Eg. Spark gaps, gas rates, burner pressures, temperatures.

Clean it out and check that everything does what it is meant to do or find specific faults.

Reply to
Ed Sirett

Ed, Many thanks for the response. I think you at=re right: there was more than one fault concurrently. All seems to be working fine now, except that the domestic hot water flow is not up to par. I conclude that the secondary heat exchanger needs descaling. I've posted a new thread on this...

Dave£

Reply to
Dave£

Is it an air flow problem ?

I had exactly the same problem on my Vaillant which also cured itself and I never found out what the cause of the problem was.

Boiler didn't fire up, I went through everything, fan, APS, changed all the pcbs (out of desperation), no joy. I called in a friend and he went through it all again and didn't find anything, we reassembled the bloody thing and it worked and hasn't failed since

Life is full of little mysteries isn't it

Reply to
raden

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