CH Pump failed?

Discussion in 'Plumbers' Talk' started by How?, Dec 30, 2009.

  1. How?

    How? New Member

    Can a CH Grundfos circulating pump fail, even though the shaft is spinning? The shaft spins, a bit of water trickles out when the silver plug is removed, so all seems normal, but the exit (nor entry) pipes are not getting very hot, the pump is though. The pipe leaving the boiler is very hot and the boiler trips out sometimes. Any ideas?
     
  2. Badges

    Badges New Member

    It would certainly be possible for the impeller to become detached from the motor shaft, but unlikely. Most likely would be the pump is airlocked. Is it mounted horizontally? Is the silver plug above or below the centre line of the pipe?
     
  3. How?

    How? New Member

    It is mounted verticaly, and water does come out of the silver plug if it is removed.

    Can the pump fail and then run hot?

    There is an air vent after the pump, one that has the vent on the side, covered by a small cap, nothing comes out of this if I undo the small cap. From the size of the vent, I would guess that it has a float in it to stop water comming out. It is not the SFD auto vent, or the smaller manual one.
     
  4. spongeblob

    spongeblob New Member

    3 main reasons
    1/ pump airlocked and cavitating
    2/shaft of pump detached
    3/Central heating systems got no water in it.

    Where is pump sited,upstairs or downstairs.
     
  5. How?

    How? New Member

    The pump is upstairs, above the boiler, all rads expel water when they are bled. The pump has water in it, the pipe does get hot after the pump, briefly, until boiler stops.

    I guess the pump could be partialy seized, so the prop is spinning, but not enough and it is generating friction that is causing it to get really hot?

    The only pumps I have seen failed, just stop working. So can they get sticky, or detach the shaft, and/ or overheat?
    Ta.
     
  6. spongeblob

    spongeblob New Member

    Your best bet is to get a time served Plumber in to sort it.Probably need new pump.
     
  7. billybongos

    billybongos New Member

    a good plumber will sort it. - There's lots of good-un's in the yellow pages - its a bit like a tombola really, you never know what ******** you're going to get! ;)

    good luck!
     
  8. How?

    How? New Member

    Ah, so you do not know if a pump can fail, yet the shaft still spins? Maybe someone else more experienced does! (it has water in it, the system is full)
     
  9. spongeblob

    spongeblob New Member

    You ungrateful *

    [Edited by: admin]
     
  10. G Brown

    G Brown New Member

    Sounds like an air lock somewhere. If the pump is getting very hot it is spinning in air.
     
  11. How?

    How? New Member

    Well G, that's what I thought. But water comes out of the vent on the pump - Silver screw, but it is getting hotter than the water pipes either side. I guess it's knackered. Can the shaft snap inside a pump?
     
  12. G Brown

    G Brown New Member

    Just 'cos some water comes out does not mean it is properly bled of air. Look for bleed valves elsewhere nearby.
     
  13. Cornish

    Cornish New Member

    From the information you have given the answer to your question is no. You have a blockage.It may be an airlock or a solid obstruction.
     
  14. How?

    How? New Member

    Thanks G,

    There is an air vent after the pump, (above) one that has the vent on the side, covered by a small cap, nothing comes out of this if I undo the small cap. From the size of the vent, I would guess that it has a float in it to stop water comming out. It is not the SFD auto vent, or the smaller manual one.

    Should this vent let water out, or how can we tell if it has vented all the air out? I was going to loosen the top.
     
  15. spongeblob

    spongeblob New Member

    All this idiot will get G Brown is scalded,hes been told to get a pro in.
     
  16. G Brown

    G Brown New Member

    Well loosen the top then!

    Blimey he ain't too smart is he!
     
  17. How?

    How? New Member

    G.....

    If I undo the small vent cap on the side of the vent, should water come out or will the float inside prevent that? If so, how is the best way to check that the auto vent is working?

    Undoing the top is an option, but maybe you, or someone on this forum has some experience of this valve and know better? You seem OK, unlike the 'blob'. but where are Cap'n leakey, Dick or the other knowledgable people tonight?
     
  18. G Brown

    G Brown New Member

    I think you need to get a plumber in if basic things like this baffle you. Sorry but that's how it is.
     
  19. Captain Leaky

    Captain Leaky New Member

    As has already been said, you almost certainly have an airlock or blockage preventing the circulator from circulating ( they are not a pump remember)

    Bleed all the obvious places, if any pipework is cold then there is your blockage or airlock.

    If you know what you are doing force out the airlock with mains water.

    However you seem to be out of your depth already so I suggest you get a plumber in.
     
  20. How?

    How? New Member

    Thanks G, you mean well.

    Not baffled at all, just a couple of questions, ignorant people are those that don't ask, or think they know everything..... and there's enough of those on here, not you though!

    It's simple really, can a CH pump still spin, yet have failed?

    and,

    What is the best way of checking that an auto vent valve is venting?
     

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