Potterton Netaheat 10/16 boiler not firing up

[andycadabra]

I have a Potterton Netaheat 10/16, with a main burner that won't fire up. I've dismantled and cleaned the burner to no avail.
The thing I've noticed is that even though the pilot light lights, there is still a spark from the electrode, which is within the flame, and a corresponding one in the electronic control box, every second.

According to the fault finding chart in the manual, it suggests that if the spark doesn't stop ' does pilot flame engulf electrode?' (which it seems to - flame is about 1 cm square), and if it does ' is electrode or lead faulty?' .
From my understanding, it's the electrode that lights the pilot so if the pilot lights why should the electrode or lead be faulty? And how should I test for any fault in the electrode or lead?

[htg engineer]

It's an HT lead, basically a safety device as well as providing the spark for ignition - it also senses the flame presence, if it doesn't sense the pilot flame then the PCB will not energise the gas valve for main flame.

I would change the electrode and lead first as they're normally to blame and should be pretty cheap - but worst case - could be the PCB at fault.

htg

[andycadabra]

Htg
Thanks for the prompt, clear and concise advice. I bought a new electrode and lead and fitted them yesterday, but still the same spark every second even though the flame is lit, and the electrode glows red hot.
With the boiler on I also tested the output voltage to the gas valve (something mentioned in the faultfinding guide in the manual), and this was zero, so I think that indicates that the PCB needs replacing, rather than the gas valve (which has apparently been discontinued anyway).

[andycadabra]

I thought I should mention that I did read on a website about this boiler-

"Common faults are fan failure, control board failure, erosion of the earth electrode on the pilot ignition"

The earth electrode is no longer the rectangular shape shown in the diagram, so has presumably eroded to a more crescent shape along one side, with a point. The distance between it and the electrode, about 2 to 3 mm, is correct and it's obviously sparking alright. Is there a chance that replacing the earth electrode, could solve the problem?, before I enter into contemplating £100 + on a new PCB.

[andycadabra]

problem solved - it was the PCB. I managed to get one second-hand on eBay for £22. Thanks for the help

[htg engineer]

Sorry I wasn't able to reply again. Been away since 29th September.


htg