Pump overrun fault.

[Robert Edkins]

I have a Glow-worm Micron 60 boiler.The pump overrun switches off correctly after 7 minutes if the central heating only is on but if both hot water and CH are on it stays on indefinately.My plumber has replaced the thermostat on the tank as he is said my hot water was too hot and the thermo was not working. This has made no difference.The temp of the hot water is just the same and the pump stiill has the fault as stated above, I would be very grateful for any suggestions before I haul engineer back in.

 

[B.O.B DOLE]

can be one of a few things its wired up wrong or the pcb or the diverter valve

 

[chrishutt]

You need to check the electrical control circuits outside the boiler, if you're competent to do that. It might be a fault with the mid-position motorised valve (if that's what you have).

 

[andsam]

If you are getting anything above 160 v at the SL connection on the boiler it will fire. The pump over run is timed so it should not matter what the temp of the water is. If you are getting no voltage on the SL and the pump continues to run it COULD be a PCB fault.

The boiler has frost protection that makes the pump run at about 6 c.
There was a problem with early PCBs that made the pump come on for frost protection at a higher temp ( at about 8 I think ). This obviously caused probs especially where boilers are positioned in exposed areas during cold weather.