Central heating pump running and sometimes the boiler too when H/W & C/H turned off.

[lookslikeitnall]

HI All,

Any help gratefully received. I have the dreaded Potterton Supima 60 boiler with an EP3000 controller (justed replaced, was EP2000).

The problem I have is that when the controller has switched off the C/ H & H/W, I often hear the water pump running and have found the boiler strike up too. I have checked the operation of the Thermostats on both the H/W & C/H and they work fine but I would have thought that these shouldn't even be looked at it the controller has no demand. I have 2 motorised valves, 1 for H/W & 1 for C/H and they operate when there is a proper demand for either H/W or C/H. When I have the problem, neither of them have been opened (they have a light on them to show then they have power to them) so I presume the water is just circulating through the boiler ? I thought that the controller would control such things so replaced the original EP2000 with a EP3000 as they use the same backplane but I still have the problem.

I have done somemore investigation and it appears to me that the boiler controls the pump ? Is this right ?If it is does this mean the problem is most likely to be the PCB in the boiler ? I have heard that reconditioned PCBs are available, does anybody know where you can get them ? Part #8407750, A new one is about =A3180.

Thanks for reading.

Cheers

Ned.

[Roger]

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The boiler probably needs to control the pump so the pump can run for a period after all valves have closed so that the water in the heat exchanger doesn't boil but the boiler shouldn't be firing in this period or any time when thermostats aren't calling for heat.

I posted about a similar intermittent problem a few days ago and you may want to visit that thread - "More boiler woes" - as faulty micro switches can produce the symptoms you describe.

Geoff may be along in a minute to say he supplies reconditioned PCBs (at very reasonable prices as I can attest) and whether a faulty board could be a possible cause.