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Water pump stopped in central heating

Discussion in 'Plumbing and Central Heating' started by MoonMan2, 1 Aug 2021.

  1. MoonMan2

    MoonMan2

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    Water pump was roasting hot but no hot hotter. I tried unscrewing the big screw and rotating pump a few times to no avail.

    20210801_143428.jpg


    Closer view:

    20210801_143259.jpg

    Allan key valves above and below:

    20210801_143334.jpg

    20210801_143322.jpg


    I guess I should just isolate the two valves (above and below), turn off electricity (of course) and then replace the pump?

    I've not done this before, though have watched a few YouTube videos. I feel reasonably confident.

    Should I replace the two valves as well?

    Any thoughts, in looking at the photos?

    Anything else I should know?
     
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  3. oldbutnotdead

    oldbutnotdead

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    Have you checked that there is power getting to the pump? If those isolation valves ( the Allen key ones) actually work then you won't need to drain down to swap the pump. If you want to replace the valves then you will need to drain the system.
     
  4. MoonMan2

    MoonMan2

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    I tried an Allen key on the bottom valve but it wouldn’t stop weeping, ever so slightly. On rotating valve back to original position it still wept.

    Draining entire system now.

    I presume to state the obvious that these valves need replaced.

    No I haven't checked if power getting to Water pump. I have a multimeter, advice on how to determine if electricity is getting to pump?
     
  5. Harry Bloomfield

    Harry Bloomfield

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    Red and black probes connected to pump terminals marked L and N, on an ac range greater than 240v (probably 500 or 1000v). With pump powered, meter should show around 230/240v, if powered.
     
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  6. MoonMan2

    MoonMan2

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    The pump is 22 years old. I'm wondering as the bottom valve weeps now that I've adjusted it and will need to be replaced before flooding the system again; I'm thinking, just replace the pump too. Afterall, it is the likely culprit.

    If after replacing the pump and valves, it still doesn't work, then it's time to call a plumber.

    At least he/she won't be able to say "The pump needs replaced".

    A plan?
     
  7. Jonnys88

    Jonnys88

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    No chance those isolation valves will work unfortunately and certainly not without weeping by the looks of it. It is likely the pump if as you say it's hot but no hot water, try the heating first though. If that doesn't work it probably is. If it's an open vented system (small tank in the loft) I'd certainly leave it to a plumber to change pump and valves.
     
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  8. kidgreen61

    kidgreen61

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    OK, I'm assuming fro pics it's a gravity fed system, ie you have a small tank in the loft that feeds the CH system.

    Isolate leccy feed to CH system
    Go in loft, and bung the outlet of the tank, bung the pipe which overhangs said tank.
    Go find a drain on a radiator, open into a bowl, you'll only lose a pint or two before a vacuum forms in system.
    With towels in place, undo pump unions, (having noted direction of flow), remove pump, replace scabby pump isolating valves at the same time.
    Remove bungs from tank
    Open vent plug on pump, & rotate impellor.
    Switch on heating/hot water.
    Charge yourself as much as you like, & demand a BJ from wife for your efforts.
     
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  9. MoonMan2

    MoonMan2

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    Yes, I do have small tank in loft. I have 'bunged' (closed off?) water supply to it and system is drained.

    Undo pump onions? That means the nuts?

    When you say "open vent plug on pump", do you mean the screw on the front to vent?

    Now which pump should I buy? This would be a direct replacement (I think, though this one says UPS2 and mine says UPS).

    https://www.amazon.co.uk/gp/product/B00EW97ZM6/ref=ox_sc_act_title_3?smid=A16P672Z5JKP2D&psc=1

    OR

    https://www.amazon.co.uk/gp/product/B08KFGKRKN/ref=ox_sc_act_title_5?smid=A1Z3GB4NCELO9N&psc=1

    Also, plan to get these valves as they look identical to what's already on.

    https://www.amazon.co.uk/gp/product/B07RCGG6XQ/ref=ox_sc_act_title_6?smid=ADSCUEKMBCQIX&psc=1
     
    Last edited: 2 Aug 2021
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  11. MoonMan2

    MoonMan2

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    Just realised the Grundfos one, the expensive one, may not be suitable - see the power ratings on the photos.

    The cheaper one, 'boiler-m8', has similar power ratings compared to my old one. Once again, see the pics.

    Am I missing something here; I need to buy the cheaper one because the more expensive one doesn't match the required specification?

    Is it to do with this UPS and UPS2?
     
  12. Jonnys88

    Jonnys88

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    UPS2 will be fine
     
  13. MoonMan2

    MoonMan2

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    Why do you say that?

    It concerns me that my old one (USP) has maximum power rating of 95W, yet the newer Grundfos USP2 only has maximum power rating of 48W.

    Are we sure the USP2 'upgraded' ?? version will do the same job as the older 95W model. I mean the older one is literally double the power rating!
     
  14. Jonnys88

    Jonnys88

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  15. MoonMan2

    MoonMan2

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    I think I'm convinced now,

    In looking at Grundfos' webpage: https://product-selection.grundfos.com/products/up-ups-series-100/ups2?tab=documentation

    It reads;

    "The (USP2) motor is based on permanent-magnet and compact-rotor technology securing silent operation and low energy consumption."

    So, I get it now, the USP2 is a more 'energy efficient' machine, doing the same job as the older USP, at a lower power rating. So would save money on operation as it costs half as much to run.

    However, I actually don't use my boiler much as I have heat pump technology in my home. So, the big question; would it be worth me paying £240 for the Grundfos pump when I could pay just £50 for the cheaper one, baring in mind that I'll only be using it a couple of times of week for an hour at a time at the most, as a top up for my heat pump set-up?

    I understand the cheaper one will not be as good quality but if I'm only using it for a tiny fraction of the time a more 'normal' household would, I'd hardly be wearing it out any time soon?
     
    Last edited: 1 Aug 2021
  16. Jonnys88

    Jonnys88

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    Yeah that makes sense, as long as you do use it every so often as it's more likely to get stuck rather than wear out if it's not as good quality. I never realised how much the UPS 2 cost, I work for housing associations so it's all paid for on accounts. The original one you have only used to be about £80. The one you are looking at is exactly the same size (130mm) so will fit in fine, definitely change the valves though so it's much easier to replace in the future. Either the same as yours or slot-headed ones, not wheel gate valve types as they are a tad longer.
     
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  17. fixitflav

    fixitflav

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    Edit - posted this before seeing previous 2 posts

    Those powers are inputs. The UPS2 is more efficient and the flow/head curves are similar (hence the power into the water). Also your current pump may not be on max (can't tell from the pics) so you have some leeway.
    I believe the story is that the UPS2 is aimed at the German market, where they may have the pump running 24/7, meaning efficiency is more of an issue. But it might be achieved at the cost of lower reliability, and there are rumours that the electronics can give voltage spikes and blow the boiler PCB. Most people here would prefer to spend a £ or 2 more per year and have greater reliability, especially as most of extra the power goes into the water as heat anyway.
    If any of that's wrong I'm sure somebody will comment!
    But having said that, I've always been a fan of Grundfos and I replaced a UPS 15-50 with UPS2 about 3 years ago and it's been fine. Cost me £95 from Anchor Pumps, Warrington so amazon's £240 looks a bit pricy.
     
    Last edited: 2 Aug 2021
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