Procombi 85HE - DHW hot-cold-hot-cold

Discussion in 'Plumbing and Central Heating' started by Pallatrax, 7 Feb 2019.

  1. Pallatrax

    Pallatrax

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    Hi guys,

    A common topic it seems - hot water runs hot, cold, hot cold...

    General advise seems to be sludged up heat exchanger or faulty diverter valve...

    Turning the DHW down has stopped the cutting out, chuntering and pressure bouncing, but I'd like the issue fixed on a more permanent basis.

    Should I treat the system with Fernox F3 (or F5?) or replace (or descale/clean) the HE?

    Many thanks!

    Tom
     
    Last edited: 10 Feb 2019
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  3. Pallatrax

    Pallatrax

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    I've now got a much better understanding on the HE (why I didn't look on YouTube!?) , so just now after advise please, on whether i;

    -remove/have removed and cleaned
    -Buy new, or
    -Try flushing system and cleaners

    Thanks
     
  4. ianmcd

    ianmcd

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    yes a partially blocked heat exchanger could cause the problems that you are having but other things can cause the same symptoms, with the system cold turn on a HW tap and when the boiler fires feel the flow and return pipes for your heating and see if one is heating up with just the HW demanded.
     
  5. Pallatrax

    Pallatrax

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    Hi, and that's for your reply. Sorry for the delay.

    The flow does indeed heat up when only asking for DHW. What does that mean, a dodgy diverter valve?

    If it helps , before the boiler cuts out the pressure bounces and it 'chunters'..

    TIA
     
  6. ianmcd

    ianmcd

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    the diverter valve on these uses a service kit, not expensive and easily fitted , I would start there, it could be the plate is partially blocked but I would start with the diverter service kit
     
  7. Pallatrax

    Pallatrax

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    Thank you very much for your help - I'll try that.
    Cheers
     
  8. ianmcd

    ianmcd

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  10. Pallatrax

    Pallatrax

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    Thank you.

    I'm a bathroom fitter and tiler by trade (so do plenty of plumbing - and not just speedfit) - so something I should tackle myself do you think?
    Cheers
     
  11. ianmcd

    ianmcd

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    yes its easy to do just make sure you cover the PCB housing while doing it to protect from damage incase a bit of water splashes on it
     
  12. Pallatrax

    Pallatrax

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    Great. Thanks again
     
  13. Pallatrax

    Pallatrax

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    Can I just check..

    I've just got off the phone to my old man, who's always been good with these things, but he's no plumber.

    The flame goes out and the boiler turns off when we lose supply of dhw. Would a faulty valve cause this?
    I know I confirmed the Flow gets hot, which is does, but with my limited access through boxing in, could I have mislead you, and heat from other sources be simply conducted when a demand there?
     
  14. ianmcd

    ianmcd

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    yes your boiler is getting too hot because the DHW sensor is sensing cooler water and the safety hi limit thermostat is over riding it and shutting the boiler off
     
  15. Pallatrax

    Pallatrax

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    Ok, so no change with diagnosis I presume?

    Thanks again
     
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