Boiler fires up then cuts out, pump makes a funny noise

Postby Pastey » Sat Nov 29, 2008 5:32 pm


I have a problem with my central heating. The boiler starts up along with the pump, but after a few minutes the boiler cuts out but the pump continues to run making a funny noise. (The noise is there even with the boiler running.) The only way to get the boiler to fire up is to turn the temperature control all the way upto 6, the max. But shortly after it fires up it stops. Then it may fire up and run for a short period again.

When the boiler ran for 10-15 mins the radiators upstairs got hot, but downstairs were cold. I have an open system i think, with a tank in the attic. I do here loud bangs and clatters like there is air in the system being pumped around. I have bled all the radiators and they are fine.

I have a Baxi boiler and a grundfos pump.

Any ideas anyone??

Sorry for the rabble

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Joined: Sat Nov 29, 2008 5:22 pm


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Postby DEEARR2 » Sat Nov 29, 2008 9:21 pm

Sounds like your pump needs to be replaced. Banging and clattering is coming from your boiler due to the the lack of water flowing through it and is expanding the high temp water into the f/e tank. Upstairs rad are heating through gravity. System is designed to be fully pumped so I would have the pump replaced as soon as.
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Joined: Sun Oct 12, 2008 8:49 pm

Postby Steve the gas » Sun Nov 30, 2008 5:20 am

Hi Pastey,

Still sounds like air in the system,did you bleed with heating on or off?
If your pump has speed settings try it faster,then pls post back
Steve the gas
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Joined: Sun May 04, 2008 7:07 am

Postby Pastey » Sun Nov 30, 2008 2:10 pm


The radiators were bleed with the heating off, starting upstairs. The pump has speed setings on it and is already on 3 the maximum. I took the head off of the diverter valve and when the central heating is switched on the motor moves to the CH position and the limit switches make. However the motor continues to drive until eventually the spring pulls the actuator back off the limits and the boiler cuts out.

I took the silver centre out of the pump and i can see that the centre of the pump rotates when the CH is on.

Could i have a control problem?

Thanks for the replys so far.
Posts: 2
Joined: Sat Nov 29, 2008 5:22 pm

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