central heating


Postby jcd » Sun Nov 09, 2008 10:48 pm

We have a indirect low pressure heating system, the central heating only manages to heat 2 out of 8 radiators even when turned to max, the hot water takes 3 hours to heat. Have checked the pump and motorised valves all ok, the flow pipe to the pump and after is red hot, the return pipe is tepid, (this is the same when heating water), even the flow pipe to most rads is hot but the return is cold. Individual radiators can be made to work if all the others are switched off. The boiler turns itself off frequently even though the return pipe is still tepid. Is there a block in the return pipe near to the boiler or in the boiler itself or is there something Im missing? Tryed to balance the system also but only seems able to heat two radiators max at any one time.
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Postby htg engineer » Mon Nov 10, 2008 11:31 am

Can you expand abit on - have checked pump and valves and are ok.

How did you check them, what did you find ????

I'd be looking towards the changing the pump.


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Postby jcd » Tue Nov 11, 2008 9:30 am

Thanks for replying, I've removed the valves to check they are clear, and checked the servo is turning the valve on, I have also checked the valves either side of the pump are clear and fully open because I thought they might be gammed partially closed. The pump is fairly new, I think under a year, but have removed the bleed screw to check and the motor shaft seems to be turning, it also seems to change speed when switched to a lower setting. Its set at max at the moment. It is however positioned vertically on the pipe with the water flowing downwards towards the motorised valves, I read that this is not ideal because of air getting trapped in the motor? It is pumping the water away from the open vent towards the motorised valves though, which I heard was correct?
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