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ABV for 42mm pipes

Discussion in 'Plumbing and Central Heating' started by DIYWell, 14 Sep 2021.

  1. DIYWell

    DIYWell

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    Big conventional boiler, no ABV in the system afaik. Are they readily available for 42mm pipes?
     
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  3. jeff the gasman

    jeff the gasman

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    Firstly, what’s an ABV?
     
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  4. DIYWell

    DIYWell

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    Automatic bypass valve
     
  5. jeff the gasman

    jeff the gasman

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    42 x 42 x 22 tee. with 22mm bypass.
     
  6. dilalio

    dilalio

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    Alcohol by Volume ;)
     
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  7. DIYWell

    DIYWell

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    I'd have thought if the boiler has such big feed and return pipes, the bypass would have been a beefier thing than the usual 22mm, but hey, what do I know.
     
  8. jeff the gasman

    jeff the gasman

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    Not much?
     
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  9. Terrywookfit

    Terrywookfit

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    A shunt pump.
     
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  11. fixitflav

    fixitflav

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    If it's an existing system and there isn't one currently, what makes you think you need one? Just curious
     
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  12. muggles

    muggles

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    The bypass only has to be able to carry the minimum volume of water required by the boiler, not the full system flow. They're specified by looking in the boiler manufacturer's instructions, finding out what the minimum flow requirement is, then finding an ABV that will deliver that flow. 28mm ones are available if 22mm really won't do it. Larger systems will almost always have a header and so an ABV is not required
     
  13. DIYWell

    DIYWell

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    That coming from someone who asked what an ABV was?
     
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  14. DIYWell

    DIYWell

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    System was fitted in the early 90s before ABVs were wide spread. There have been instances when the TRVs have closed off enough to force the hot water out the overflow on the roof. Crossed my mind having an ABV added might help.
     
  15. fixitflav

    fixitflav

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    Interesting. Usually there is at least one rad without a TRV (the one where the roomstat is), so the boiler gets minimum flow if all the TRVs close. But if all have TRVs and all close, I can't see why the F/E tank would overflow, if that's what you're saying. Though the boiler wouldn't like it. As a stopgap, you could remove the head from one TRV.
     
  16. jeff the gasman

    jeff the gasman

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    You need to sort out the hydraulics rather than finding a way around it.
     
  17. ianmcd

    ianmcd

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    An ABV wont stop pumping over, you have bigger system design problems than that
     
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