Central heating tripping out in cold weather

  • Thread starter Thread starter Pnb
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Pnb

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Hi everyone,

I am having trouble again with my central heating with an issue that only seems to occur when the outside temperature drops near freezing and the heating is working hard.

My system is a typical gravity fed with header tank in the loft and boiler in the garage, has two separate 2 way valves for the CH and HW (S plan??).

The issue I am having is in the morning the CH fires up fine, same at lunchtime and also at 4pm when its programmed to start for the evening. However in the evening period it will commonly run fine for 3-4 hours and then once the house is up to temperature the thermostat stops calling for heat and the valves close as I would expect.

The problem comes when it calls for heat again say 30 mins later and the valve opens in the airing cupboard but the CH pump seems to have no real go about it. The pump sounds like it is running but very quietly and you can feel the vibrations off the pump when you touch it. However no HW seems to circulate the system at all and after a few minutes the boiler will shutdown as I assume none of the heat is being dissipated. Turning the thermostat up and down to move the two way valve seems to make no difference to the pump wanting to run properly.

The only way I can currently get the pump to start working properly again is to switch off the whole CH/HW system as the mains switch, leave it 30 seconds and switch on again. This then spurs the pump back into life properly and its very noticeable that it makes a lot more noise than normal and sounds like it is working really hard for the first couple of minutes before it settles down again.

To the experts out there does this sound like I've got a dodgy pump? It has always seemed noisy to me compared to previous houses I've lived in and the problem only occurs on the coldest nights in winter, was wondering whether the pump could be overheating?

Thanks in advance for any help, hope the above explanation makes some sense.

P.s The pump is a British Gas (grundfos) Multihead 6, dates from 2008 I think
 

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