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.
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.
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...