Grundfos 15-60, will not switch off. All aspects of plumbing questions and answers, help, tips and information

[Gobstopper]

Can anyone help, my system had a new circuit board fitted in Jan after being out of action for about ten days.
Everything was working fine but I have noticed that the pump does not shut itself down when the heating switches off at night.
Prior to this I did notice that the system was noisy when starting up, quite a loud banging noise, although this seems to have stopped now.

[Kenj]

It is quite normal for the pump to continue to run for a couple of minutes after the boiler has turned off, with fan assisted boilers. This is to dissipate heat from the small heat exchange chamber.
If there is no bypass circuit to cool this water, then the pump may continue running for a good bit longer, and the pump may make a groaning noise.
If your pump runs all the time that the central heating is on, then either the wiring is wrong or the circuit board controlling the pump is faulty.
To check for this try turning the boiler on from cold with both the CH and the H/W thermostats turned right the way down. If the pump is running then the wiring or the pcb are faulty.

[Gobstopper]

Thanks Ken

I switched the power off last night before going to bed, as pump was still
on at 11 although heating and water go off at 10, Icos Boiler showing 'C' with green burner LED flashing on and off.

Anyway came down this morning at 6 powered up and now seems OK.

So hopefully thats it, very strange !

[Gobstopper]

Same problem again had to switch power off to pump before going to bed last night !!!

Pump stays on with 'C' showing on the boiler readout and green LED burner
indicator flashing on and off.

There is some noise from boiler when started up like a 'clanking' noise.

The system was off for ten days when PCB board packed up and had to wait for replacement, would it need flushing after this length of time ?

[Kenj]

Being off for 10 days should not be problem. Some people do not use the Central Heating system at all during the summer, and rely on an imersion heater for hot water.
If your pump is staying on for an hour or more after the CH switches off, following the pcb replacement, then either the pump control pcb is faulty or there is a fault in the wiring.