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Automatic By Pass Valve

Discussion in 'Plumbing and Central Heating' started by Sandy43, 13 May 2009.

  1. Sandy43

    Sandy43

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    I have an Automatic By Pass valve model SBV22 by SUNVIC.
    I am trying to find a simple way to calibrate setting so that it opens when
    two ports valves in s-plan systems are shut (no heating or hot water)
    and minimum flow when any of the heating or hot water is on.

    The method described is quite complicated such as to set 20% above the
    normal pressure when working so this does not open premature.

    I find difficult how you would determine these setting figures.

    I saw an other Auto by pass in Srewfix and that comes already set at 2 bar and the setting can be varied.

    Is 2 bar a nominal value ?
     
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  3. Fluffster

    Fluffster

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    Generally an open vented system will run around the .5 bar and a sealed system hot about 1.5 to 2 bar.

    Pete
     
  4. mogget

    mogget

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    I'm not sure how this would relate to a bypass valve, as your average 15-50 pump only produces a differential of 0.5 bar on maximum setting.

    I set mine using the unscientific method. First I set the bypass valve to maximum (ie, shut), and turned the boiler stat right down. Then I put the system onto pump overrun, and slowly turned the valve down until there was flow through it - the sound changes as flow begins. With the boiler stat back up you can check by feeling the pipes for heat.
     
  5. D_Hailsham

    D_Hailsham

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    Allow heating to cool down
    Set ABV to max (7)
    Turn on heating with all TRVs and zone valves open.
    Adjust the ABV until you can just feel the pipe after the ABV getting warm.
    Turn the valve back slightly so it closes
     
  6. doitall

    doitall

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    That's the easy way DH, and good enough in most domestics.

    Everything on full with the by-pass closed, then open the bypass slowly until you feel a flow through it, turn it back one full turn.

    Job sorted.
     
  7. D_Hailsham

    D_Hailsham

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    The Sunvic is only one turn from open to closed!

    [​IMG]
     
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  9. doitall

    doitall

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    Right, I've always used the AVDO
     
  10. Agile

    Agile

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    I would recommend a better way to set it by closing all except TWO of the TRVs and then adjusting the ABV until it just starts to allow a small flow through it as evidenced by the outlet getting warm.

    Then leave it in that position!

    Turning back one turn is very hit and miss. Particularly if the valve only has one turn!

    Tony
     
  11. gas4you

    gas4you

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    Honeywell's instructions are to close all rad valves, turn the ABV until it just starts to pass hot water, then turn back 1/2 a notch.

    I more often than not find it ends up set at about 3.5.
     
  12. D_Hailsham

    D_Hailsham

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    Which is the only one where the instructions distinguish between a bypass used to maintain the minimum circulation through the boiler (left picture) and one used to limit the differential pressure across the radiator circuit (right picture).

     
  13. bengasman

    bengasman

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    Your pumps are better than mine mate.
    The very best I can achieve under optimum circumstances is about 0.4 bar on a sealed system, which is the same as open vent by the way.

    Forget about all the numbers as they are not important.

    Easy way to go about is to turn the resistance to way more than needed.
    Stop the flow by closing all valves, or any other way you fancy, start the pump, slowly lower the resistance on your bypass until it opens. Now go about 0.2 below that.

    Repeat process at annual service to assure proper working is maintained.
     
  14. DIYnot Local

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