Potterton Performa 24 - Not Firing

[tcanact]

Hi All,

I've just moved house and after moving in I found that the boiler had the flame failure light lit. After following the fault finding section of the manual decided to purchase a replacement (2nd hand) PCB.

This fixed the problem for a short while, but I found that the controls for the CH / DHW were fairly unresponsive, for example when turning the CH to maximum the boiler wouldn't fire, but if DHW was demanded it would fire.

The boiler then stopped working again, and following the fault finding again led me to the safety thermostat, which had been activated. Resetting this returned the boiler back into life, but only for a short while, and now it doesn't attempt to fire at all.

I have done a number of checks and all appear to point back to the PCB, but before purchasing a new one I was to be sure that this is the cause of the issue.

The checks so far are as follow: -

Pump and fun appear to run, primary flow switch operates. There doesn't appear to be any voltage to the gas valve or igniter.

One other odd thing that’s worth pointing out, I've installed the original PCB that would display flame failure every time, and now this isn't happening. Perhaps this helps with the diagnosis?

Any thoughts would be appreciated.

Thanks

 

[tcanact]

Does anyone have any thoughts on this?

I have since checked the airflow switch, testing with a meter shows that the switch goes between the terminals. I have also replaced the overheat stat as this was thought to be faulty, but appears not to be the case.

Thanks

 

[tcanact]

Just to point that that I have resolved the problem. This was caused by a melted venturi. I hope that this was caused by a fault on the original PCB (that was reporting flame failure) rather than the replacement!