Central heating pump wiring

10 Feb 2009
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United Kingdom

My central heating system has a pump in the boiler but an auxiliary pump has been fitted to boost the flow.

When the central heating is off the auxiliary pump still runs and causes vibration in the pipe work.

Is it possible to wire the pump into the heating zone valve so it turns on and off with the central heating?


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Boiler make and model please, would be very unusual to have your set up but it is possible

Thanks its a Worcester-Bosch Greenstar 24i System ErP condensing boiler on an S plan system.


you shouldnt need two pumps with that boiler, you have a pipe sizing or blockage problem somewhere, you would be much better getting the fault sorted rather than using an additional pump, two pumps can cause you problems
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It’s a new installation!

The plumber said it was needed because of the number of rads?

It all seems to work ok apart from the noise. If the aux pump is turned off not all the rads get hot.

Has he ballsed something up?


Call worcester technical and ask them if they would recommend a secondary pump in your situation , I think I already know the answer, the telephone number is in the installation service manual, the boiler is a 24KW boiler and the internal pump is designed to circulate this amount of heat you really shouldnt need an additional pump (circulator) commercial systems use multiple pump scenarios but rarely does a domestic system require it

Thanks will do. Could the extra pump be removed and the boiler configured to manage without it?



Thanks it’s 200m2 with 13 rads.

Wonder why he thought it necessary if it isn’t?

Can I the pump just be turned off temporarily or will it restrict the flow?

It will need to be valved-out to prevent bypass flow through the redundant pump.

@Nozzle , think we are thinking of two different scenarios , I thought the OP has an S plan with an additional pump on the CH side, how would the pump act as a By-Pass and if it was valved off the the CH wouldn't work, the pump has to be removed and a section of pipe cut in surely ?
I was imagining you had a pair of pumps in parallel, as that increases flow throughput - I evidently didn't pay enough attention to the detail in the OP!


I’ve turned off the second pump and checked the boiler pump setting it was on the highest constant pressure setting (4) so I have changed it to variable (0). The rad that didn’t seem to get hot without the 2nd pump is now heating up. Have I done the right thing?



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