potterton boiler

[J.Roberts]

Don't want to go over old ground but I have been experiencing problems with my Potterton Suprima 30 boiler. It is just over 3 years old but has been playing up for months. It constantly cuts out and needs to be re-set manually (when the red light flashes). I have been told by different gas fitters it's either the PCB (quoted £250.00 for a new one) or the valve in the airing cupboard (£90.00). The bloke said he knew it was the valve because both the inward pipe and the outward pipe are both very hot, which they are. I live on a newish Barratt estate and it transpires many of my neighbours have been experiencing similar problems. It was suggested I get in touch with CORGI, which I have done, but any other advice on the problem (in laymans terms) would be greatly appreciated 'cos I really do need to get it fixed as the problem is occuring several times a day. OK, my missus says I've got to sort it out.

Many thanks.

 

[CH4]

The problem that you describe usually occurs when the water flow rate through the boiler is too low. This can be caused by a build-up of sludge in the system (due to internal corrosion), a heavily scaled heat exchanger, a faulty/inadequate pump or an incorrectly adjusted bypass valve.

The bypass, which can be just an ordinary gate valve (but is an automatic relief type valve on newer installations), connects the Flow and Return pipes - somewhere after the pump and before the first radiator. This provides a path for the pump to circulate the water when all the thermostatic radiator valves have shut off the flow. Thereby giving the boiler time to shut down gracefully, rather than being cut off by its overheat thermostat. You could try opening the bypass a little more - having noted its original position.

Another possible cause of the problem could be that the pump-overrun is not working. This keeps the pump running for a short while after the main burner switches off, to remove residual heat from the heat exchanger. You can test this by turning the boiler off, when the system is hot, using the room thermostat (if in CH only mode) or the timer (if in CH and DHW mode). If the pump stops immediately then the pump-overrun controller could be faulty (meaning a new PCB) or the pump may not have been correctly wired in the first place. The pump should be wired back to the pump-overrun connector - provided within your boiler, and not wired directly to the zone valve in your airing cupboard.

 

[J.Roberts]

When I turn the boiler off using the thermostat when in CH mode, it takes 5 seconds to go off, but when I turn the thermostat up again I get the red flashing light. If I time it correctly and give the boiler a good old fashioned whack with my fist just as the burners about to strike up (when the green light is flashing very fast) it kicks in no problem. Also, when the boiler has shut down I've noticed that the valve in the airing cupboard becomes quite audible. Does this point towards a circuit board problem?

 

[CH4]

A pump-overrun of only 5 seconds seems a little short, and could indicate a faulty temperature sensor. However, since giving the boiler a thump alleviates the problem, a loose connection to the temperature sensor or a dry joint (a badly soldered joint that has now oxidised) on the PCB, may be a more likely causes.