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Vaillant Ecotec plus 637 - Pump Over run

Discussion in 'Plumbing and Central Heating' started by RK_London, 13 Oct 2021.

  1. RK_London

    RK_London

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    I have a Vaillant Ecotec plus 637 boiler fitted 2 years. I also went from a vented to unvented hotwater system and had underfloor heating fitted in a converted garage.

    I understand the pump overrun is supposed to protect the boiler heat exchanger from damage but where does the heat go? Reason I ask is when the boiler burner stops and goes into pump over run every cycle, all my radiators and pipes start banging. This never happened with my other boilers and I have no idea what's going on. (All the radiators have had air removed and have been balanced. Also the TRVs are bi directional )

    Does anybody have any idea what's going on?

    Thanks in advance.
     
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  3. Harry Bloomfield

    Harry Bloomfield

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    It's supposed to cool the heat exchanger down, by continuing to pump it to where the original call for heat came from. Idea is two fold - to both cool the heat exchanger down gracefully and save some money by making use of the heat you have paid for.
     
  4. Mottie

    Mottie

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    Do you have your auto by-pass set up correctly? When on pump overrun, mine just circulates it around the bypass and heat dissipates as well as equalling out the flow and return temperature of the boiler heat exchanger. Something like that anyway! Sounds like yours is not going anywhere.
     
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  5. RK_London

    RK_London

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    Thanks Harry Bloomfield - so I assume heat is lost through the radiators.

    Mottie - how do I check if the auto by-pass is set up correctly?
     
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  7. Mottie

    Mottie

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    Got a picture of it?
     
  8. lightning

    lightning

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    Your by pass will be in your boiler
     
  9. RK_London

    RK_London

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    Are there any settings in the boiler that need to be looked at?
     
  10. RK_London

    RK_London

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    Looking at other posts online it seems the 637 ecotec is a powerful boiler that does have problems losing the extra heat. The banging when boiler is in pump overrun seems to be loudest in the two radiators without TRVs ( bathroom and hallway).

    I've lowered the power setting of the boiler to 22KW from 37Kw. Would adjusting the pump speed make any difference ( right now its set on auto and operates at 15%)?

    As the bypass valve is in the boiler I won't be able to look at this
     
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