Passive recirculation loop with mixing valve at heater?

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by whackit, May 5, 2014.

  1. whackit

    whackit New Member

    Apr 14, 2014
    Los ANgeles
    Hi All,

    I'm remodeling my home and am planning on designing the supply around a passive recirculation loop. I have one in my house now and it works great. The new home meets the requirements (water heater at lowest point). My question is this, we are planning on using a high efficiency gas water heater which uses a mixing valve on it's supply side. I'm wondering if this will interfere with the function of the passive loop? Any ideas?

  2. hj

    hj Moderator & Master Plumber Staff Member

    Aug 31, 2004
    Cave Creek, Arizona
    The mixing valve operates by adding cold water to the hot as it flows through. ANY circulation system works by moving the hot water, but since there is no "flow" the cold water does not get added so the circulation temperature will eventually equal the hot water heater's temperature, unless the flow control modulated the hot water to shut if off if the temperature got extreme, which few do.
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  4. Terry

    Terry Administrator Staff Member

    Aug 17, 2004
    Bothell, Washington
    I think you will need to pump it, and add an aquastat to prevent overheating the water. Grundfoss makes one that cuts the pump off at 108 degrees.
    You can't pump the recirc without the aquastat.
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