Potterton Suprima 80l only igniting when cold.

[kmacandie]

I have a 5 year old Potterton Suprima 80l that has been serviced annually since installation. Four weeks ago I noticed that all the radiators in the house were cold. The boiler, which is in the garage, had gone to lockout but started up again first time when I pressed the reset button. Woke up the next morning to a freezing cold house. Boiler locked out, restarted straight away when reset. A few hours later the house was freezing. Again, the boiler had locked out, but re-ignited immediately when reset.

The boiler is covered by our home contents insurer for up to £500 of repairs and so I gave them a call. Over the past four weeks, the insurer's approved engineer has attended and the following parts have been replaced:

-pump
-zone control valve actuator
-thermistor
-PCB (yes, the new one, brand new from the manufacturer)
-fan assembly
-air pressure switch

I still live in a freezing cold house.

I have spent hours, sitting in the garage, watching what happens. The boiler always ignites normally from cold. It will run through a few normal cycles, the house will start to warm up and then, when the boiler is hot, the ignition cycle starts but only gets as far as the fan coming on. The fan runs for about 30 seconds, no ignition clicks are heard, no sparks seen inside the boiler, the fan stops and the boiler locks out. At this point, holding the reset button for the diagnostic mode gives 2 flashes in keeping with an ignition failure. Trying to reset the boiler whilst still hot fails - the red light starts to flash rapidly and I have to let the boiler cool for about half an hour before I can reset it and start the whole happy process all over again.

The insurer tells me they have spent over £1000 and I have spent £200 on parts and labour to get no further forward. The insurer now tells me that my boiler is "beyond economic repair" (although they can't tell me what is wrong with it) and that they will not fund any further repair attempts.

I would be quite happy to pay someone who knows what they are doing to come and fix it or at least confirm that it is irreparable, but the chance are that when someone attends, the boiler will either be running fine because I have reset it or the boiler will be cold and start up without any problems, resulting no doubt in the engineer looking at me as though I have a head like 2 dicks before billing me for a call-out fee and suggesting delightedly that I call them back out if I have any further problems - which I will.

If I need a new boiler, then I need a new boiler (albeit a condensing one that will doubtless freeze up the next time we have temperatures of -17C), but I would hate to go to such lengths if all I need is, for example, a new HT lead or ignition.

Has anyone heard of such a problem before, where the boiler only ignites when cold but not when hot? Could it be a hairline crack in the ignition. The gas valve sticking when hot? How on earth would I find out?

I'm in the West End of Glasgow. Please, if anyone can help, I'd really appreciate it.

Thanks for any help.

Kerr MacAndie

 

[petej]

As an installer I do not do maintenance on boilers but it sounds to me that the boiler is overheating or has a faulty over-heat switch.
You say if the boiler is hot the reset switch will not reset until the boiler has cooled enough to allow this to happen. so the switch is still in overheat mode.
When the boiler turns off does the pump keep running (on pump over run) to take any residual heat from the boiler ? if it doesthe heat has to have somewhere to go ! If you have a "S plan" with 2 zone valves when the stats or timer switch off the valves will shut and if you have no "Bi-pass" valve the heat cannot circulate from the boiler.
If all this checks out I would certainly be checking the over heat switch.

Pete

 

[sonara]

fault ignition flame sensor ,also change the reset hi-temp cut out switch as mentioned above, check the pump is working when it cuts out, pump could overheat and seize and therefore the boiler cuts out. Make sure at least one radiator has NO thermostat valve and is fully open, this acts as bypass.