Pump continuously running - WB Greenstar 30CDI

[MenBehavingBadly]

Hi all

WB Greenstar 30CDI
Fitted in loft
Unvented cylinder also in loft

The pump on our boiler seems to be continuously running even with water and heat turned off (at programmer) - there's a constant slight vibration from the boiler so I think it must be the pump running - also the temp gauge is showing around 30deg

We did have a new valve fitted about a year ago - could a mistake have been made with the wiring when this was done ? It may have been doing it since installed but only noticed it recently

Any advice please re. what to investigate - would prefer to have a look myself (obvs nothing gas related)

Many thanks in advance

 

[Harry Bloomfield]

The pump on our boiler seems to be continuously running even with water and heat turned off (at programmer) - there's a constant slight vibration from the boiler so I think it must be the pump running - also the temp gauge is showing around 30deg

Asking, not telling.....

Wasn't there an issue with the pump relay contacts welding up, on these boilers, such that the pump would run continuously?

The fix, was a 'snubber' across the relay contacts..

 

[bsr]

I also have this. I fitted the snubber which removes any stray currents from the wiring. That didn't work.

Engineer said the other cause was corrosion on the pump PCB from a slow leak around the gland. Replacing the pump also requires PCB replacement so you're talking best apart of £1k!

I still have an intermittent fault with the pump running

If you want to try the cheap option it's a Worcester Bosch 87161092750 RC Device. About £20 and takes two minutes to fit.

 

[Harry Bloomfield]

If you want to try the cheap option it's a Worcester Bosch 87161092750 RC Device. About £20 and takes two minutes to fit.

That seems to fix another issue, of the constant call for heat, from the valve.

The OP's problem is similar, but just affects the pump remaining running, when it should be stopped. This is caused by the contacts, of the pump relay, welding up, due to the back emf from the pump motor, when it is switched off. A snubber network, across the pump terminals, help to prevent this.

As a quick, dirty, and temporary fix, the OP could power down the boiler and give the boiler a bit of a thump. That might free the contacts, until the next time they weld up.

 

[bsr]

Ah cool, in which case I want to try that too. Should I use the same snubber or is there a specific part?

 

[Harry Bloomfield]

Ah cool, in which case I want to try that too. Should I use the same snubber or is there a specific part?

I'm not even convinced we are taking about the same boiler/problem. All I recall, was that it was a common problem on a WB boiler.