Potterton Netaheat 16-22 not firing (updated)

I drained the system to repair a dripping rad valve. When I refilled and turned system back on (HW/CH) the 3 amp fuse next to the boiler blew within about 5 seconds. This fuse also covers the circuit to the airing cupboard where the cylinder, pump and heating controls are, so everything stopped working.

With trepidation I replaced the fuse and switched back on. The timer, pump, motorised valves and cylinder and room stats are all working but the boiler does not fire up.

My guess is that the fuse blew because an electrical component in the boiler had just died. Is there an easy way to identify which component this is by doing a continuity test? I removed the lower panel to expose the wiring. The relay looks a bit black inside. Can I test it easily?

[17.30] I have now tested the basic function of the relay by turning up the boiler thermostat from off with the power on and the bottom cover off. The relay clicks visibly and audibly but there is no subsequent sparking (as far as I can tell) or firing.

If the part which caused the fuse to blow is a different one, is it straightforward DIY to change an electrical component once identified?

I have bled the air from all the radiators and the air from the bleed point on the piping from the cylinder in the airing cupboard and do not believe there to be any air in the system but perhaps there was when the boiler tried to fire up the first time and that caused the component to "go".

Any advice would be welcome.

I don't think too many people would give you any advice on this boiler. Try doping a google search on fatalities.

I have a NETAHEAT 16-22 that has had start up probs in past.. i have just turned my boiler stat up - exhaust fan starts, after a few seconds relay operates, clunk as pilot light valve operates, sparking , pilot burner on, then main burner valve , then ignition - - I have changed the PCB in the past to correct no ignition. Later I had problem with fan running but relay not operatind due pressure differential valve not working - bad flexible pipe connections to pressure valve also valve clogged up ,,,,hope this helps

Thank you for your reply.

mikesin said:

I have a NETAHEAT 16-22 that has had start up probs in past.. i have just turned my boiler stat up - exhaust fan starts, after a few seconds relay operates, clunk as pilot light valve operates, sparking , pilot burner on, then main burner valve , then ignition - -

Click to expand...

I only hear the relay click when I turn up the stat but then nothing, - no fan, no ignition. However meantime the pump pumps away merrily as long as HW and/or CH are set to ON via the timer.. I had thought that under normal working conditions if the boiler were not running the pump should switch off, so I am extra confused.

mikesin said:

I have changed the PCB in the past to correct no ignition. Later I had problem with fan running but relay not operatind due pressure differential valve not working - bad flexible pipe connections to pressure valve also valve clogged up ,,,,hope this helps

Click to expand...

I don't believe I have a pressure differential valve as it is an open vented system or am I misunderstanding you?. Where did you find a PCB?

mtl.. With all due respect you sound to be doing a lot of guessing about the operation of your boiler.

These boilers can be EXTREMELY DANGEROUS, please (for you and your families sake) don't attempt any diy repairs.

Be aware that "mikesin" is not CORGI registered and is a user giving you what he thinks is useful advice.

However he has not mentioned and is probably blissfully unaware of the dangers associated with this model.

It can kill people!

Tony

oh dear!

Agile said:

Be aware that "mikesin" is not CORGI registered and is a user giving you what he thinks is useful advice.

However he has not mentioned and is probably blissfully unaware of the dangers associated with this model.

It can kill people!

Click to expand...

Thanks for all the warnings. I have seen lots of similar warnings on this forum and others. Rest assured, I am certainly not about to take the case apart. I will under no circumstances attempt anything gas-related. I am guessing that I have an electrical fault. I have a healthy respect for electricity but can change a component while taking the necessary precautions.

I changed the relay (worth taking a chance for £6) but it did no good. As the fan is not kicking in when the relay clicks, can I assume that the pressure switch is unlikely to be the problem and it is more likely to be the fan (which I am fully aware I cannot attempt to change myself)?

I would just like to so as much as I can safely to make a likely diagnosis before calling out a heating engineer, by testing the electrics with a multimeter to the terminal block. As I said in my initial post I am not sure which wires to test and was hoping that someone might be able to make suggestions.