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Vaillant Ecotec 937 Plus - very little and inconsistent hot water

Discussion in 'Plumbing and Central Heating' started by V6Mark, 30 Jul 2015.

  1. V6Mark

    V6Mark

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    Hi - the combi generally works well (F22 from time to time), no fault code displayed but very little hot water coming out of taps/shower - it's hot but just a trickle. Have just had some work done in the house including a radiator removed - heating is off though. Could it be heat exchanger needs cleaning, an airlock (due to rad removal) - any ideas/advice? (Boiler pressure is around 1.3/1.4bar so should be fine)
    thanks in advance
    Mark
     
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  3. Agile

    Agile

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    The hot water routing is separate from the heating system so that is not going to have affected it.

    But check all the isolators under boiler are fully on as a first step.

    Tony
     
  4. Dan Robinson

    Dan Robinson

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    The filling loop might not be back where it's supposed to be.
     
  5. bazdaman

    bazdaman

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    Plus 1 on the filling loop
     
  6. simond

    simond

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    Just to be sure, the cold water supplies aren't similarly low flow rate? Is there a tacky in line scale reducer on the water inlet to the boiler?
     
  7. V6Mark

    V6Mark

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    Thanks chaps, the cold water supply is a much higher flow rate - the low HW flow output is recent. It's now cycling through to S26 and then the flame symbol goes out. No hot water. No fault code. No clue. if by the 'filling loop' you mean the two grey taps underneath, then yes - they are both closed.
     
  8. Terry lambert

    Terry lambert

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    Take the knobs off and check that the brass nibs are in the right orientation, the knobs round off and so don't move the nibs properly
     
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  9. ScottishGasMan

    ScottishGasMan

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    Facing the boiler, looking at the filling valves (two grey handles) the one on the right(middleish) is the cold water inlet, ensure as said its in the correct position and also that the flat bladed isolator on the same brass piece is open.

    the boiler will cycle flame off as theres not enough water water comming out your tap for it to stay on, but the boiler its self does not control the flow rate, it simply heats whats moving through it, and if theres a low flow rate it has nothing to heat.

    sure its an 837 and not possibly a 937? as that can be a different kettle of fish?
     
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  11. simond

    simond

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    Ah yes, the corroded pipe in the heatstore.........
     
  12. iamlee2002

    iamlee2002

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    I had an issue like this a while back only my water wasn't getting very hot when opened taps fully on our vailant eco max 824 a rubber pipe was blocked. It caused the boiler to make hell of a racket lol vibration noise. Had my so called mate to try and fix it from British Gas, changed heat exchanger , pump , then he cocked the board up replaced that also poweflushed system which was very quick 2 hours tops. In the end he left me with no hot water or heating as the 2 x 22mm inlet outlet pipes he turned the isolation nuts and rounded them off. So told him to go then I bought that short length of rubber piping for around 10 pound and that was all it was fitted that was gutted i didn't do that in first place . Was without boiler for 4 weeks in freezing winter
     

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  13. V6Mark

    V6Mark

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    I'm such a numpty - it is indeed an ECOTEC 937 PLUS - not an 837 - sorry to have wasted your time and kind help - so would there be other things to check?
     
  14. Tipper

    Tipper

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    I had this very problem on my 937 last year...

    It's collapse of the plastic internal outlet pipe from the store. Sometimes lower flow rate was OK but mostly the flow started OK for a couple of seconds and then restricted sharply. In the end HW was almost non-existent. The plastic degrades and allows the flow of water out of the store to collapse the pipe as it deteriorates and crumbles. You may even get 'limescale like' pieces of plastic coming out of the HW taps as the pipe falls apart.

    Simply cured with a new outlet pipe...Part No: 0020138668...but a beggar of a job to change if access under the boiler is restricted, luckily mine could be done without disconnecting and unhanging the boiler!
    But I went for a fixed price repair by Vaillant Service which also meant they upgraded certain other components (changed other internal flexible rubber hoses to copper, replaced leaky filling valves, etc) whilst they were at it and all within the same fixed price.

    Most likely it will take two visits as the part doesn't seem to be carried on their vans.:(

    Good luck!
     
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  15. simond

    simond

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    Groundhog day
     
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  16. Dan Robinson

    Dan Robinson

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    Great.... An unannounced title edit after several otherwise decent replies.
     
  17. V6Mark

    V6Mark

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    A title correction after realising my error, acknowledging the assistance offered, and apologising.
     
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