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Radiators are slow at heating up

Discussion in 'Plumbing and Central Heating' started by ian1904, 22 Jan 2009.

  1. ian1904

    ian1904

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    I noticed that about three weeks ago the radiators were not getting hot, and so the house was a bit cool. If I left the Honeywell boiler timer control set to constant then the house would eventually warm up. (The timer is working OK). The boiler is a Potterton Suprima circa 1997 and is firing up fine, but only for short periods. Currently set at about 3/4 of maximum heat output. Radiators do not appear to need bleeding and the water is nice and clean looking. Radiators are circa 1974 and do not have individual thermostats. Thermostat is Honeywell circa 1997. System has never been flushed, all radiators heat up fine, apart from one which needs re-balancing, but I can live with a temperate bedroom ;) Hot water for showers etc is fine. Water tanks in loft both look fine.

    So moving on the pump, a Grunfos UPS15-50x18 Mk11 probably 1974. If I switch the pump off, remove the central bolt, insert a screwdriver into the pump and rotate the pump anti-clockwise as per the arrows on the pump, refit, switch on, then the radiators heat up quickly.

    So is this likely to be some form of solid/sediment interfering with the pump, do I need a new pump, or something else. :?:

    Thank you
     
  2. kevplumb

    kevplumb

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    sticky pump possibly

    as in replace it :idea:

    or you could try turning the speed up ;)
     
  3. mogget

    mogget

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    It's possible that the pump bearings are getting a bit stiff, and also the pump electricals may be getting tired causing it to have less 'oomph'.

    If it's never been flushed, I would add some X400 to the system water and run the heating as normal for a couple of weeks. Then drain down, change the pump and refill, adding inhibitor (X100 or Fernox).

    This should give the best chance of reliable service in the future.
     
  4. gavinda

    gavinda

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    sounds a sensible plan. remember to read the faq's on diy flushing as a few folk miss some key points and waste thier time. but from the sounds of it you've got a reasonable clue of what you're undertaking.

    good luck :)
     
  5. Agile

    Agile

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    Your posting ends up a bit vaguue!

    You seem to be saying that if you spin the pump then the radiators heat up quickly.

    But you dont say what setting its on and if you have listened to it when its running fine and if it sounds different when its not fine.

    You listen to it with a mechanical stethoscope or a stick etc.

    Tony
     
  6. ian1904

    ian1904

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    I never knew that there were settings on the pump. LOL. I have just moved it from 2 to 3. The sound is smooth, a gentle hum as far as I can tell.
     
  7. ian1904

    ian1904

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    Well I am able to approach the issue reasonably logically, and follow a flowchart:) However I am not most practical person when it comes to DIY. If it comes to flushing the system I will find a professional.
     
  8. mogget

    mogget

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    The fact that the pump was working properly, and then didn't, does suggest a fault.

    However, even if it is slowly failing it may keep going for quite some time just by turning it to the next higher speed.

    A full flush may be a bit involved for a plumbing novice. If you're able to change the pump, a 'routine clean' such as I described should be easily within your capabilities.
     
  9. Agile

    Agile

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    Well you have now increased the pump speed!

    But what difference has it made to the heating?

    Tony
     
  10. DIYnot Local

    DIYnot Local

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