Potterton Performa 24 not igniting

[drand]

Hi

My performa 24 combi refuses to fire up when CH/DHW is demanded. I have been through the fault finding in the manual but it hasn't helped-
DHW for example:
pressure switch operates diaphragm OK
microswitch provides 230V
pump runs
fan runs
air pressure switch provides 230V
ignitor does NOT receive 230V.

However, I have replaced PCB (according to manual) with same result.

Over-temp thermistor hasn't tripped, correct resistance from temp sensor, correct DC volts to gas valve.

Any ideas?

If I provide 230V to the ignitor the system works OK, but requires ignitor to be on constantly to sustain the burner - is this correct behaviour? has the flame-sensing electrode gone, what voltage should I see on it when burner is lit?

Really appreciate any suggestions.

Cheers.

 

[Agile]

I think there is a manually reset o/h stat on the flow pipe on the left. Its a switch not sensor. Have you checked its continuity?

You clearly have enough electronics experience and in fact more than most people fixing boilers. However, I am unable to give you the help you need on an open forum as we are not permitted to give advice on DIY gas work. In fact you have already exceeded the access to combustion/safety components.

In your case ( only ) I might be prepared to give you some suggestions if you called me from in front of the boiler.

Tony

 

[linkyplumb]

Did you reset the boiler after insatlling the new PCB?

 

[Agile]

Thats a good point often forgotten by professionals alike. Even though its in the instructions with the new pcb which are of course designed to be thrown away without reading.

A professional however, knows that its necessary to turn to the reset position and hold it there for about a minute rather than the few seconds mentioned in the instructions.

Tony

 

[drand]

Thanks very much for reply.

I think there is a manually reset o/h stat on the flow pipe on the left. Its a switch not sensor. Have you checked its continuity?

Yes there is continuity across this switch.

 

[drand]

Did you reset the boiler after insatlling the new PCB?

Yes, reset by holding selector knob against spring pressure for >2 seconds.

Thanks for the suggestion.

 

[drand]

Thats a good point often forgotten by professionals alike. Even though its in the instructions with the new pcb which are of course designed to be thrown away without reading.

A professional however, knows that its necessary to turn to the reset position and hold it there for about a minute rather than the few seconds mentioned in the instructions.

Tony

OK,

thanks for that. Held against reset for 1 minute but no change to symptoms.

 

[drand]

In your case ( only ) I might be prepared to give you some suggestions if you called me from in front of the boiler.

Tony

Tony,

Thank you for your help so far.

If you consent to advice over the phone, please let me know when is convenient for you (think you can pm me if you accept friend request, or reply).

If not, I understand why and no hard feeling.

Daniel.

 

[Agile]

Look at my profile for tel number.

I cannot say what I am doing at any time of day so wait until its convenient for you and try a call. Dont leave any voice message.

Tony

 

[drand]

Thanks to Agile for help.

Turns out the venturi in the flue was distorted through heat, thus not allowing pressure differential to activate air switch. Engineer hadn't seen this before.

 

[monoxide62]

air pressure switch provides 230V

Not if fault with venturi , seems your original diagnosis was floored , i which case impossible to fault find over internet.