Central heating water pump running continuously

[platty76]

Hi everyone, I hope there is someone out there who can help with this.....

Our boiler (a Potterton HE Plus) has worked fine for years. However in Nov last year the PCB had to be replaced as the boiler was not firing when the thermostat called for hot water........fair enough, job done, all working fine.

However, ever since I've noticed the water pump (a Wilo Gold RS50) carries on running almost all the time as its developed a small rattle noise, the problem is I'm not sure if it has always run 24/7 or if I'm only noticing it now following the PCB change because of the rattle?

I've dropped the thermostat level so the boiler only comes on for hot water twice a day but it's still running!!

Any ideas why this would be, and/or how I can work out what the problem is?

Cheers!!

Potterton Promax HE Plus

• platty76
• 24 Apr 2016

Wilo Gold RS50

• platty76
• 24 Apr 2016

 

[dilalio]

Pump is getting a permanent feed from wiring.
If boiler is also firing uncontrollably then motorised valve(s) are faulty.
If just pump then likely pump overrun stat is faulty.

 

[dilalio]

Or it might be the board again!

 

[platty76]

Hi dilalio, if when you say permanent feed you mean the mains wiring to the pump then yes that's correct.

Boiler is not firing unless the therm kicks in and asks for hot water.

As I say it only seems to be an issue with the pump running continuously..... Is the overrun stat part of the actual Wilo pump (sorry if daft question, I'm no expert!!).

Cheers

 

[dilalio]

The pump runs when boiler is firing. When boiler stops firing, pump should continue to run for about three minutes, to dissipate heat around the system and away from the boiler - this is known as pump overrun.

On some boilers, this is controlled by thermostat in the boiler, on others by components on the PCB.

Having looked up the MIs for your boiler, it would appear that pump overrun is controlled through the PCB and this is at fault, rather than a thermistor/overheat stat/overrun stat!

Multimeter testing on the PCB is required to suitably diagnose the fault!