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Differential Bypass Valve ?

SUPER DAN P&H Member Posts: 48
What is the purpose for installing this valve by the boiler connecting the supply and return lines? How does it work? Thanks, Dan.

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  • Paul48
    Paul48 Member Posts: 4,469

    Typically used on high head loss systems with zone valves and steep curve circulators, such as radiant floor or fan coil.If you picture the system running with all the zone valves open, there is a certain number of gpm flowing through the whole system. If one zone valve closes the gpm increases to the remaining and can create velocity noise. The differential bypass is basically a spring-loaded gate, that opens with the added head, and provides an alternate path.
  • SWEI
    SWEI Member Posts: 7,356

    in most cases, by ECM smart circulators like the Alpha, Stratos, and BumbleBee.
  • RJ_4
    RJ_4 Member Posts: 484
    another reason

    All low volume flow heating boilers (Teledyne Larrs, Raypac ) need continuous flow through the heat exchanger, flow should never be reduced below 30%.  Systems using zone valves,zone pumps or 3 way valves can experience reduced water flow through the boiler and high temp. rise across the boiler,  high temp. rise can cause condensing in 85% eff. boilers.  Installing a balancing valve between supply and return allows setting a constant flow across the boiler.

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    SUPER DAN P&H Member Posts: 48
    thanks guys!

    It makes sense since Ive seen alot on Hi Effiency systems.

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