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Valiant Ecotec 837 - no hot water.

Discussion in 'Plumbing and Central Heating' started by cdbe, 7 Apr 2018.

  1. cdbe

    cdbe

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    Hi, my sisters 5 year old boiler has the above problem. Happened out of the blue (not intermittent). We suspect diverter valve, however there is no water at all (bar a brief trickle when first opened) coming out of any hot outlet, my only experience is of the diaphragm type where you just get cold water if the microswitch doesn't operate.

    Is it likely to be the diverter - does all water flow stop when it fails? Heating side is fine, no fault codes, no-one has messed with it and it's had no other issues since new.

    Thanks for any suggestions, she's on holiday, her engineer is very busy but had a quick look and "thinks" it's the diverter but obviously we'd like to be sure.
     
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  3. terryplumb

    terryplumb

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    If no water at all ,dry ,from hot taps that's not a diverter problem ,or do you mean you are getting water flowing from taps and they are just not hot ?
     
  4. cdbe

    cdbe

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    Hi Terry, I've checked as she's hard work! She's now gone from initially saying it delivers no hot water, then to saying no water at all, now she says it's a very slow trickle of hot water! (It gushed out before) - not entirely helpful. Also this thing has a big tank with it that I suppose could deliver a fair old trickle of stored hot water without the boiler operating properly.

    Thanks.
     
  5. terryplumb

    terryplumb

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    Well that's about as clear as mud mate !! :LOL::LOL:. I' m non the wiser !!
     
  6. picasso

    picasso

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    Ask if she or anybody has topped up the boiler pressure, if one of the top up valves is left open it cuts off the cold water supply to the boiler and hot taps.
     
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  7. fixitflav

    fixitflav

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    None of this would affect the flowrate from the hot taps. If there's a boiler problem, eg low pressure or diverter valve fault, there'd still be flow, but cold.
     
  8. picasso

    picasso

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    you don't work on many vaillants do you ?
     
  9. cdbe

    cdbe

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    Boiler's in loft and they don't mess with it, they've checked the system pressure (it was ok) and for fault codes (none).
    I can see how difficult it is to fault diagnose over the 3rd hand over the internet but I think it's worth me advising not to just get the diverter changed without some further investigation.

    Thanks.

    I will update when the engineer has had a proper look.
     
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  11. fixitflav

    fixitflav

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    No, to be honest. If that's wrong please explain. Always glad to learn!
     
  12. heatservice

    heatservice

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    When the filling loop valve (in the centre) is opened it isolates the CW flow to the plate heat ex therefore no water flow at hot taps but a dribble of water would suggest a blockage in the CW inlet filter or a scaled up plate heat ex possibly caused by having the preheat turned on.
     
  13. dilalio

    dilalio

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    Sounds to me like first issue was “no hot water” but cold water coming out of taps (diverter or blocked plate hex); then ‘someone’ fiddled with whatever valves they could get hands on in an attempt to fix issue and in so doing, left filling loop cold inlet valve in off position and now symptom is no water at all! :)
     
  14. fixitflav

    fixitflav

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    OK, thanks for that. I assumed the DHW could flow through the 2ndary h/ex and out to the tap without restriction, whether or not the boiler was available, but apparently not.
    However, I found this flow diagram on Vaillant site, and I can only see the flow sensor in that pipe, but the drawing may not be comprehensive.

    [​IMG]
     
  15. heatservice

    heatservice

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    Your DHW is heated indirectly in the plate heat ex (PHE) meaning the boiler fires up if a reasonable flow is detected when a hot tap is turned on, the hot water then produced by the boiler is diverted to flow through the PHE where the heat is instantly transfered (water to water) to the mains flowing water which becomes your DHW, the diverter valve does not itself come into contact with the mains water so has no effect on the DHW's flow rate, I hope that make some sense.
     
  16. fixitflav

    fixitflav

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    Reading that again I'm more confused. I haven't looked closely (haven't needed to) but I thought the filling loop was on a tee from the mains cold pipe, with 2 ordinary 2-port valves in series, so opening valves wouldn't affect cold water flow to the 2ndary h/ex. Used to have a braided flexible, which was supposed to be disconnected after use, to avoid risk of leaving the fill running. But on later ones (like my son has) it's solidly piped.
    In any case, I can't see any suggestion either valve has been left open (open to fill, that is), but if it has it's easy enough to correct.
     
  17. fixitflav

    fixitflav

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    Yes, I understand that, but I don't see why my post #6 is wrong, unless there is a valve in the DHW pipe somewhere, which closes when eg the boiler is off-line or failed.
     
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