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Banging when central heating turns on and radiators not getting warm

Discussion in 'Plumbing and Central Heating' started by gmc1, 24 Feb 2018.

  1. gmc1

    gmc1

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    Got a odd problem in that 2 or 3 weeks ago whenever my central heating turns on (either at 4am or 5pm) I get a lot of banging in the pipes. After a few minutes the banging disappears however there is no water flow and none of the radiators get warm.

    There is Drayton controller connected to the Grundfos Alpha2 pump. When the timer kicks in the power to the pump is turned on (Power light and C2 light comes on) but none of the radiators get warm. (The hot water taps work fine though)

    Everytime this happens if I switch off the central heating on the controller for a few seconds (Until I see the power light on the Grundfos go off) and then on again, the pump switches on again, banging noise stops and hot water flows through the radiators.

    It will stay working for day or two or three and then the problem returns. Banging and no water flow until I switch off and on again.

    I first thought it was kettling but don't think this is the case now with it working after I power off and on.

    Could air in the pipes be causing this? Suspect Grundfos?
     
  2. rochdalegas

    rochdalegas

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    Sounds like the pump may be sticking. Have you had any problems with sludge in system
     
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  4. oilboffin

    oilboffin

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    Sounds like it's running out of water is it a sealed system or gravity if it's gravity then the feed pipe might have a blockage and not topping up the system if it's sealed it may need topping up and the pump bled by unscrewing the screw in the middle of the pump till water comes out also bleed all the rads you could have a good lot of air in the system.Bob
     
  5. rochdalegas

    rochdalegas

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    They are "self bleeding" pumps so no bleed screw I think they suggest running it on higest speed for a couple of days.
     
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  7. gmc1

    gmc1

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    Thanks for the replies. I haven't drained anything so not sure about the sludge. Will check all radiators for air.

    I'll also try running it on full speed for a few days and see what happens.
     
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