Potterton Not Firing Without Reset Switch

[keithmdw]

As of today, my (troublesome) Potterton boiler has started not firing of it's own accord (sometimes at least).

The pump and 3 port valve do their stuff, but no ignition. However, if I press the reset button on the front, it fires immediately.

When it did it, the DHW was on as well as the CH - not sure if this is relevant. I have CH only on now so will see how it goes.

What could this be? Is it a simple thing, or a big problem?

Don't want to wake up and find it has refused to fire when it is below zero.

Thanks in advance.

 

[Rob]

what model?

 

[keithmdw]

what model?

Promax HE

 

[keithmdw]

Little bit more infor after observation this evening.

In normal operation, the boiler fires, runs for a while, then turns off (but the pump continues). Then a while later, the boiler re-fires, and the sequence repeats. Now this is perfectly normal.

However, when the boiler shuts down now for a while while heating, it won't re-fire, because whatever is broken or playing up won't fire the ignition (I guess).

Pressing the reset switch fires it immediately.

Also, I bled the rediators and noticed that one in particular (second in the chain I think) had a LOT of air in. This radiator was removed a couple of months ago to drain the system when a new 3-port valve was fitted but is not leaking (nor is anywhere else) and up until today was getting hot just fine.

 

[ChrisR]

I would be suspicious of the flow switch in the boiler. Iirc it has a pair of wires going to a 2 way plug on the pcb, which you can get at.
I'd check with a meter to look for any voltage across the switch - which would mean it wasn't seeing the pump flow.
If you think the pump is actually working you could short out the switch to test things..

 

[Agile]

Chris, I think that this is a heat only model with no flow switch.

I also think that its an ignition lockout although the OP does not give the fault code light sequence.

Tony

 

[ChrisR]

It has a flow switch, and no fault indicators!

 

[keithmdw]

Thanks for the replies.

Agile: If this is an ignition lockout what could cause it?

ChrisR: What does the flow switch do, and why would it cause this problem?

I will call the landlord and get him to send a gas man round (I assume it's a CORGI guy I need as opposed to a plumber) but would like to be able to give him as much info as possible to save a wasted day off.

For reference, I have not so much as had the cover off the boiler. There are no obvious fault lights etc. visible from outside it. Whether there are any under the cover I do not know.

I noticed last night, only once I must add, that the flame thorough the window was orange rather than the usual blue. Not sure what this means. I only saw this once, and the rest of the time it was blue.

Another bit of info I have observed which may or may not have any relevance. Last night, about 30 mins before goign to bed, I flicked the reset switch and it fired the heating up. Within about 20 minutes it was off (as normally) and the pump was still running, however, as since this fault started, it never fired back up. I flicked the reset switch again and it fired the boiler, before turning it back onto timer in the hope it fired in the morning to heat the house.

This morning, the boiler did indeed fire of it's own accord, but when it finished it's "burn", it never re-ignited all morning (and was on for 2 hours). However, the pump continued running for the entire time - I guess because it kept trying to heat the house with ever cooling heating water.

I have left it off now, without pressing the reset switch at all, and tonight will see if it fires of it's own accord without a reset - I suspect not however and so am not looking forward to going home to a cold house when it's currently 0C outside!

This heating system has been nothing but trouble since we moved in. One thing after another.

 

[Vic Spanner]

The combustion box door seals need to be checked for soundness.

 

[keithmdw]

Are the things which could be at fault likely to be things a gas engineer would have on his van or be able to get quickly or am I likely to have to wait for parts to be oredred (if needed of course)?

 

[keithmdw]

New symptom. It just fired (after reset switch), then went out after a few seconds, then fired for a few second, then went out, then fired, and went on like this until I stopped it.

Does this indicate anything new?

EDIT: After leaving it off again for a while, it fired up using the reset switch again without going on/off/on/off. Guess it may have just been overheating?

I have an engineer coming tomorrow. Just hope it's simple and he carries (or can quickly get hold of) parts for it.

From things I have read on here and other sites, and from chatting to people, I guess (though might be completely wrong as I know nothing about these things!) that it could be:

- the flame sensor (but why would the boiler light with reset - surely it would be off completely)

- the flow switch (but again, surely this would cause either all or nothing - why would reset have an effect)

- the ignition or master PCB (and I hate to say it, but why would reset make a difference again)

- and finally, the combusion box seal

Just out of interest, what exactly does pressing reset do? It's clearly not mechanical as it just clicks off and on, but what is it doing?

 

[baxpoti]

Start with replacing the electrodes!!!

 

[keithmdw]

Engineer is coming tomorrow afternoon.

Is this likely to be an "on the van" item? It was 0C this morning, with tomorrow expected to be sub-zero, so I want this fixed as quickly as possible.

Are Potterton a particularly poor/cheap make? I have had all kinds of problems with this system.

 

[keithmdw]

Boiler is now fixed. Thanks to everyone who offered advice.

In case anyone else experiences the same problem, the engineer replaced a couple of parts:

- the condensate tray with a new (now modified) part and cleaned out the pipe from it as it was draining really slowly.

- the combustion chamber door (complete with electrode and sensor) as the seal was leaking as it had started to crumble - this was also a modified part.

Problem solved!

He told me either of these faults could have caused the problem - I had both faults at once!