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Is a 22mm differential valve the same as a 22mm bypass valve

Discussion in 'Plumbing and Central Heating' started by Chivas69, 1 Feb 2015.

  1. Chivas69

    Chivas69

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    I need to swap over my bypass valve and just wondered if the differential valve is the same thing?
    Basically it sits between flow and return of the two manifolds in my bore system! It has been leaking and the pipes are extremely hot after the bypass valve meaning water is getting through, this in turn means my heated water is circulating straight back to the boiler and overheating the boiler!
    I think this valve was blown due to expansion vessel having no air in it!
    Expansion vessel is now sorted so I'm hoping replacing this valve will stop the water circulating back to boiler and enable it to travel down the notorious to the roads!
    When looking for a valve, differential is coming up, seems to be a similar valve but just wanted to make sure they are the same thing!
    Thanks
     
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  3. stardanny

    stardanny

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    Photo please?

    Daniel.
     
  4. Madrab

    Madrab

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    Nope, a differential valve allows pressure to be balanced between 2 different parts of a system, say the flow and return pipe of a CH system.

    An autobypass is a protective component that allows a flow to be maintained through the pipework/boiler when all other valves on the system close down, basically to avoid overheating.
     
  5. Chivas69

    Chivas69

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    Ah right! makes sense!
    Thanks for the replies!
     
  6. picasso

    picasso

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    The full name is differential pressure bypass valve so the valve can be used as a bypass valve or differential valve, same thing.
     
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  8. Chivas69

    Chivas69

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    Cheers guys!
    I just got a like for like part and changed it! Heating is great, hottest the rads have been for years!
    Well happy as I was so close to spending 2 grand on getting a new boiler fitted!
     
  9. Madrab

    Madrab

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    Apologies, but have to disagree. I wouldn't think you would use a DPCV (Differential Pressure Control Valve) as an autobypass normally. The valve and it's companion are usually used to match flow and pressure from one side of a system to the other, e.g say allowing a pump or 2/3 port valve(s) to be equalised at both ends, reducing the load and making them more efficient. More suitable for high workload, large systems I would think.
    I wouldn't think it would be situated inline on a bypass pipe run as it doesn't work by pressure passing through the valve acting directly on the valve as an auto bypass does. That being said, could it be used, possibly but would need some clever siting of the companion and the linking tube.
     
  10. Chivas69

    Chivas69

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    Cheers yeah, I got the auto bypass valve and it's sorted it out lovely now!
     
  11. picasso

    picasso

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  12. Madrab

    Madrab

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    Fair do's Picasso, more than happy to put my hands up to that one. Need to read the post properly :)

    Only reason I went that way is because I was asked about the control valves by a customer before, guy had a massive house and it had a PDCV valve in place to balance the system and he was wondering what it did and why it was needed.
     
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