Pump not over running after boiler switches off

C

CouchPlato

Joined
24 Feb 2020
Messages
12
Reaction score
0
Country
United Kingdom
Hi all

I have a Worcester Bosch Greenstar Ri boiler.
When the boiler switches off, the central heating pump switches off at the same time and the boiler makes a grumbling chuntering sound for a few minutes. I believe this maybe due to the fact that the pump is not running for another 3 minutes to dissipate the heat as it says it should do in the boiler installation and maintenance instructions.

I suspected this might be due to some incorrect wiring so I've had a look at the wiring centre and have drawn a diagram of the connections.
But as far as I can see, everything is correctly wired.
The live pump and neutral pump wires appear to be connected properly to the boiler.

So I'm a bit baffled as to why the pump switches off when the boiler does.
If anybody can see a problem or has any other advice I'd be very grateful to hear it.

Thanks a lot!

Heating.jpeg
 
Last edited:
Sponsored Links
I think I follow your wiring diagram.
It looks like there is no permanent live supply to your boiler.
This is required for the pump over-run to work.
Though looking again it also looks like there is no neutral either, as you just show the neutral connected to the pump, but there must be if the boiler is working.
 
Last edited:
Johnmdc said:
I think I follow your wiring diagram.
It looks like there is no permanent live supply to your boiler.
This is required for the pump over-run to work.
Though looking again it also looks like there is no neutral either, as you just show the neutral connected to the pump, but there must be if the boiler is working.
Click to expand...

Oh sorry I should have said that the boiler has a separate permanent Live, Neutral and Earth connection which I've just added to the diagram.
Thanks for looking though.
 
Last edited:
That wiring layout is highly dangerous...you should only have a single source of mains power...either to the boiler (and then to the wiring centre) or vice versa.
Engineers have been electrocuted due to thinking the systems isolated not realising there are multiple sources of 240V.
Get it sorted out asap.
Who installed it like that?
 
Sponsored Links
Gasguru said:
That wiring layout is highly dangerous...you should only have a single source of mains power...either to the boiler (and then to the wiring centre) or vice versa.
Engineers have been electrocuted due to thinking the systems isolated not realising there are multiple sources of 240V.
Get it sorted out asap.
Who installed it like that?
Click to expand...

Apologies, my diagram was crap and I had left out the fact that the boiler and wiring centre share the same same mains source. I've updated the diagram. Thanks for your input, much appreciated.
 
Pump overrun is controlled by a timer on the boiler PCB, which is why the pump is wired to specific terminals on the PCB (terminal block ST2). As the pump works OK when the boiler is on, there's a good chance that the timer is fault. Unfortunately this means a new PCB. WB do a fixd price repair.
 
Pcbs on these are relatively inexpensive...far cheaper to get an independent eng. to look at it.
 
D_Hailsham said:
Pump overrun is controlled by a timer on the boiler PCB, which is why the pump is wired to specific terminals on the PCB (terminal block ST2). As the pump works OK when the boiler is on, there's a good chance that the timer is fault. Unfortunately this means a new PCB. WB do a fixd price repair.
Click to expand...
Thanks for the advice, I'll look into getting somebody to look at the PCB.
 
If the boiler is still under warranty you should not involve a third party. Get the installer back, he will handle the warranty claim for you. You should not be charged - unless the fault is not boiler related.
 
It turns out that the boiler has been wired differently to what is described in the manufacturers instructions.
For some reason the installer had connected the permanent live mains feed to the boiler's switched live/call for heat terminal, and the switched live/call for heat wire to the boiler's permanent live terminal.

So this is either done intentionally, or it's a cock up.
Is there any possible reason why a boiler would be wired like this on purpose?
 
Only an ignorant or incompetent installer would make that mistake.
 
D

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
You must log in or register to reply here.
Sponsored Links

Similar threads

J
Central heating pump runs all the time.
Replies
1
Views
1K
sambotc
S
clarkerothwell
PUMP OVER RUN
Replies
7
Views
2K
twgas
twgas
S
Worcester + Wave = constantly running pump ??
6 7 8
Replies
106
Views
31K
Paul Sheard
P
R
pump running on and on and on !!!!!!!
Replies
14
Views
955
picasso
P
S
boiler pump over run problem - advice needed
Replies
3
Views
2K
Slugbabydotcom
S
Back
Top