boiler fires up for a minute then dies and its -3 outside!

Discussion in 'Plumbing and Central Heating' started by laris, 29 Dec 2005.

  1. laris

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    Hi there

    typically on the coldest day of the year my system plays up....i recently bled a couple of radiators and the pump a few hours before that (with it still on). I turned off the boiler and then back on and since then it fires up for a minute then stops. the pilot is always on and i have a gravity fed system and a old cast iron boiler. When it "dies" it makes a sound like a kettle boiling with little water in it and there is a rattling, presumably from the cylinder. If i leave it alone for half an hour then turn the system on again it fires up again then dies after a short while etc

    i have a feeling this all might be down to air but have no ideas (i read somewhere that bleeding the pump can introduce MORE air into the system)- any help would be much appreciated
    ta
     
  2. Agile

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    It sounds as if your pump is not turning.

    you need to look at the "Sticky" information to see how to check its turning.

    Tony
     
  3. laris

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    thanks Tony

    i have tried to search for the sticky on pumps with no joy (but have read a number of interesting posts dealing with the complexities of effective communication and modern man along the way !)

    how do i go about this and apologies if i am being thick

    BTW my pump has a nut not a screw slot in the middle should i just be able to remove this completely to check if the pump's turning

    Leigh
     
  4. Agile

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    I have described how to check your CP53 type pump myself twice over the last few days.

    Do a search of my recent posts to find them.

    Tony
     
  5. captain_pugwash

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    it does ineed sound like the pump - had identical problem a while back myself and it was the pump that had seized up. with no pump turning the water in the boiler just boils causing almighty banging and whistling usually and then the boiler usually ****s itself down with an overheat protector

    You can see if the pump is turning by removing the large case - it will dribble some hot water so have a cloth at the ready. If its turning then you will see the pindle rotating. If its not turning you may be able to free it by using a large screw driver and turning it - when mine went it jammed up solid and I wasn't able to budge it, in which case you will need to get a new one.

    It's a five minute job to swap if you have the right unit. Just drain down the bloiler, take the control cable off and then use an allen key on the four bolts securing it.

    If the pump is turning and you're still getting the cut out then there is a blockage somewhere else - possibly in the pipes from the pump to the heat exchange - this will mean you flushing the boiler with some Fernox type cleaner
     
  6. Agile

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    This is the blind leading the blind!

    You pump is different from his!!!

    Follow my advice relating to the CP 53 as fitted to the Potty Puma boilers!

    Tony
     
  7. laris

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    hi

    yeah its definitely the pump (spindle turning when undo nut,pipe below hot/pipe above cold, sludge visible when crank turned manually)

    i'm going to have a crack at cleaning pump/pipes today - failing that getting a replacement

    don't bleed the system with pump running me thinks :)
     
  8. Agile

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    There are two questions! Is the pump shaft rotating as checked when you engage the nut by withdrawing it?

    If not then is it supplied with power when it should be and although powered its not turning? If this is the case the capacitor may have failed but its usual to replace the whole pump head.

    Tony
     
  9. laris

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    thanks for your help - had to get a man in in the end

    was sludge in the pipes....
     

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