worcester 28si (british gas c1)

[Access Gas]

Hi not sure if anyone has had a similar problem.

call for CH or DHW boiler fires - flame rectification does not sense flame spark electrodes keep firing - boiler goes to lock out after 3 attempts

cleaned flame rectification same issue

replaced flame rectification same issue

replaced pcb - boiler works for 1 week then same issue

after fiddling about with wires today i realised that as soon as the prongs on the pcb back plate touch the contacts on the pcb the problems occurs (when the pcb back plate is removed the boiler works fine)


The earth contact goes direct to the back plate, then a wire from the back plate to the boiler case, then the prongs on the back plate earth the pcb and then the pcb earths the pump.


saying that - i diconnected the earth wire from the back plate fired the boiler with the back plate removed and it worked, then fitted the back plate still with the earth removed and the spark electodes started firing again even though the flame was on and in high rate.

it seems when ever the earth conects to the pcb the flame rectification gets knocked out

im not an electrician by trade but am now realising to be a good boiler engineer you need to be a good electrician too.