C/H pump always on

[JasperW]

Hi,

Our central heating system is working, but I have noticed that the central heating pump is always on. We had a new boiler fitted a couple of years ago (Worcester Bosch 40 CDi condensing). I have discovered that the pump remains on even if the timer has switched off the CH and HW. The pump only stops running if I actually switch off the boiler (using the power switch at the from of the boiler).

Am I correct in thinking that if the boiler is not running then the pump should be off? I only noticed it because I woke very late one night and heard a faint hum which I tracked down to the pump still running. Given that the CH & HW had been off for at least 4 hours I assue that if it is controlled by the boiler then it should have been switched off sometime after the CH & HW had been stopped. Now that I have noticed it I am 99% sure that it never gets switched off by the system. Apart from the electricity required to run the pump I am sure it cannot be an enegy efficient way of running the system.

Assuming that something is amis; is the central heating pump controlled by the boiler or by the timer? I am going to phone up the firm that fitted the boiler to ask their opinion but I would be interested in any comments/advice from people in the know.

Thanks

Jasper.

 

[ChrisR]

SHould be controlled by the boiler. Trace the wire.
Often an installer will find himself having to runa a horrid long run of cable extra, so they cut corners.
There's probably a way round it using radio control - would need to know all your layout and wiring.

 

[JasperW]

Thanks for the info.

Update:

I called the installers and they were very straight forward, "No the pump should not do that", "If it is a problem with our original installation (done in 2006) we will fix it for free, but we will have to charge you £90 call out in case it is some other problem". Which seems more than reasonable but still leave me at risk of a £90 call out charge.

I then called Worcester Bosch (I have a 12 month maintenance contract for the boiler with them) explained the situation and they said they would send an engineer around to look at the system and would not charge me even if the problem was due to faulty installation (although obviously would not fix it for free).

My main concern was that both sides might blame the other and I would be left with an expensive bill to fix the problem. A the moment everyone appears to be bending over backwwards to be as reasonable as possible. How refreshing!

 

[JasperW]

Yet another update.

The Worcester Bosch engineer came around and checked out the boiler which was (as I suspected) fine. However he said that the lead for the pump overrun was not connected to the boiler (although I am not sure how he knew it was the overrun lead)!

This makes me think that the pump is directly connected to the mains input and not to the boiler which I assume it should be. BTW the configuration of my heating system is an "S" plan with two zone valves for heating and hot water. The only way I can currently turn off the pump is to unplug the heating system from the mains or to switch off the boiler from the boiler control panel.

I guess I could reconnect the pump to the live switch (orange wire) of the valves so it switches on and off with the boiler. But I have read that is is a very bad idea as the overrun is need to cool off the boiler after it has been switched off and switch the pump off at the same time as the boiler can shorten the life of the system.

I have downloaded the Worcester Bosch 40CDi installation manual and I can find nothing in the manual about where to connect the pump to. Does anyone know if it infact supports a pump overrun? The WB engineer was obviously expecting to see a pump overrun feature and I have also heard that WB manuals leave something to be desired in terms of their completeness. On the installation guide I can see what appears to be a terminal block (ST19) which has no information about what it does, also the service guide does talk about pump overrun times which makes me think that there should be one on the boiler.

The truth is that I would rather get the installers over to carry out the work but given that they appeared to f**k up in doing the installation I would rather understand what the solution is before I get them around to try and correct it.

 

[D_Hailsham]

I have downloaded the Worcester Bosch 40CDi installation manual and I can find nothing in the manual about where to connect the pump to. Does anyone know if it in fact supports a pump overrun?

See page 27 Para 8. An external pump has to be wired to terminal ST2.