Boiler doesn't think it's lit

[Al]

Potterton Prima F60.

Sometimes the boiler fires up correctly, but the igniter keeps firing every few seconds as if it doesn't 'think' the gas is lit. Usually does this a couple of times, and then is happy.

Occasionally, it will turn the gas of, refire (and light correctly) and then turns the gas of and repeat a few times.

I'm guessing that the thermocouple is on the way out (it is sitting happily in the flame and getting hot).

However, when our usual gas fitter came and had a look, he noticed that the flame was lifting, and found that the concentric section of the flue had corroded away to dust, so the exhaust was being recycled into the inlet causing a poor burn and reduced pressure, causing the ignition repeating problem. Flue conversion kit fitted, and sure enough problem solved. For a few days.

Now the problem is back, and very intermittant, but clearly there is still a fault. Is it the thermocouple, or sometthing more expensive ;-)

Cheers,

Al.

[Mogga]

Did your gas fitter not know?

[Al]

He was thrown by the rusty corroded flakes around the flue. And he was right - It was like a lace curtain when it came out :-(

Problem now is that the fault only occurs at weekends, or betwwen 10pm and

6am ;-) Basically, sods law applies.

I dare say he could replace umpteen PCBs etc, sensors, whatever, but he's never witnessed the fault and is loath to change/charge without some first hand evidence.

Basically, I was asking if this is known fault with this boiler (or any other boiler) before spending money :-)

Al.

[geoff]

In message , Al writes

There is no thermocouple

Lack of flame sensing is down to

1) defective pcb (407677) 2) HT lead broken - not conducting the flame sensing current 3) electrode not in the flame 4) flame still lifting 5) bad earthing (6) Live and neutral reversed)

[Ed Sirett]

My guess of a descending order would be

4, 3, 2, 1, 5, 6

I'm truly amazed that a replacement flue was available for this model. Also corrosion of the flue is a fairly rare occurrence and might indicate a more serious problem with boiler. I'm thinking may be something to do with the fan or the heat exchanger?

[Mogga]

Get a camcorder!