Pump running on and on, help?

[keekster64]

I have a problem with my central heating system. Its a regular boiler (Baxi), not combi, with open header tank and separate hot water tank. I have replaced the pump and electric values recently as they were failing. Now I have a new problem. In the evening when the system switches off, ie the boiler goes off and the valves close the pump keeps going circulating the water (via an additional piece of pipe before the values). If I switch the advance button/or manually open a value the water starts to circulate the system again and if switch it off again manually at all stops. But it wont do it by itself, Whats going on???? I thought that if the values closed the circuit would be cut and the pump would stop, how is this possible, all help greatly appreciated.

 

[oilman]

You need to wait for the gas guys for boiler info, but some boilers have a pump overrun function to ensure the boiler is cooled properly. This might be malfunctioning.

 

[keekster64]

Thanks. Have delved into the manual, and found reference to the overun. Its seems to be controlled by the thermostat. £23 for a new one is not bad.

 

[AnonymousImport]

If it is a pump over run boiler, guessing it could be a Baxi Solo the circuit board controls pump over run. Sounds like circuit board is not shutting pump off, could need new circuit board, 'expensive'!

 

[copp]

pump over run caused by sticking relay on pcb
managed to purchace one for one pound