Potterton Suprima 80 - PCB fuse blows repeatedly

Rosarius · 4 Apr 2007

I have a 7 year old Potterton Suprima 80 and recently it stopped working suddenly. Power and light were still on at the timer switch/controller but all lights on the boiler went out.

I found the fuse on the PCB (T3.15) and sure enough it had blown. I replaced that fuse twice(!) and both fuses blew within minutes of the boiler being powered back up.

I have just replaced the entire PCB, and its fuse blew straight away when I powered it up. Before I invest in a visit from the plumber, are there any obvious causes of the fuse blowing like this I can eliminate?

baxpoti · 4 Apr 2007

Suspect, in no particular order

pump

fan

gas valve

Soggy_weetabix · 4 Apr 2007

baxpoti said:
Suspect, in no particular order

pump

fan

gas valve

Very acute faulty finding.

If all engineers were like you eh?

Dave

baxpoti · 4 Apr 2007

Soggy_weetabix said:
Very acute faulty finding.
If all engineers were like you eh?Dave

And your 'acute' diagnosis is?

gas4you · 4 Apr 2007

Remove pump live wire from terminal block and switch on boiler. This will prove/eliminate pump

Soggy_weetabix · 4 Apr 2007

baxpoti said:
Soggy_weetabix said:

Very acute faulty finding.
If all engineers were like you eh?Dave

Click to expand...

And your 'acute' diagnosis is?

Just highlighting that your very 'vague'

Not really the response I would expect from someone with your knowledge.

Free advice yes, but non descritpuble comments about boiler and system components helps no man (or woman).

D minus

Must do better Baxipotty

Dave

Slugbabydotcom · 5 Apr 2007

Measure and record the resistances of the fan, pump and the top 2 and bottom 2 pins on the gas valve with the supply wires disconnected and report back.
If these are 'reasonable' then its time to look for a direct short in the wiring to these and any other 240V wires within the boiler.
If your replacement PCB was part number 5111603 then these come with a new wiring harness. It could still be possible that one of the wires to the fan has melted on the combustion chamber cover or been stripped when they were pulled through.

Rosarius · 5 Apr 2007

Firstly, I am not trained in either plumbing or heating, and am merely an enthusiastic tinkerer attempting to save some money.

I guess the first reply was a little too vague - but helpful nonetheless - and the most recent is way beyond my capability.

I successfully replaced the PCB, and armed with a bagful of little T3.15 fuses, have been experimenting with a) starting the boiler then b) turning on either the heating or hot water then c) trying so see what blows.

It would seem that the offending article is the pump. In fact, having completed the above experiment above 3 times, the pump now doesn't come on at all. With the pump dead, the fuse never blows, and the boiler turns on etc. I can hear the zone valves opening/closing as per normal, but the pump is dead.

Plumber time.

Slugbabydotcom · 5 Apr 2007

With the power off remove the cover of the pump to see if you can see anything obvious.
Check the wiring to it.

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Potterton Suprima 80 - PCB fuse blows repeatedly

Soggy_weetabix

Soggy_weetabix

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