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P/S, Taco 3-way, mixing, Parallel supply

lekpeter Member Posts: 35
Thank you for the input.

I thought that with the valve's hot supply and its cold return and the zone's return tee'd together to the boiler manifold's crossover, when the valve's hot side opened, the baseboard zone circulator would induce flow into the zone through the valve's center mix port, at the same time releasing the same amount of cool return into the boiler return. With the hot side of the valve closed, the zone loop would simply circulate around itself.

Thanks again.


  • lekpeter
    lekpeter Member Posts: 35

    I have a multi-zone radiant system using injection mixing, with each tapped off a parallel piped reverse-return boiler loop manifold, and also an indirect DHW.

    I'm installing a cast iron basboard zone along with a TACO I-series 3 way mixing valve for added control.
    All the supply and return on this zone are 3/4" pipe.
    The 3-way TACO valve is 1/2"

    I'd like to pipe the 3-way using it as an "injection mixing type device, but the instructions don't illustrate that installation. In other words, I don't want all of the zone's flow to go thru the mixing valve. Instead, I'd like the valve to inject hot water as needed.

    I photographed a crude mock-up and was interested in comments on if it would work or not. If not, why?
    The black tubing represents the baseboard and all connections to the boiler and zone manifolds are closely-spaced tees. Also, I didn't illustrate the needed thermal trap on the return leg.

  • Ted_9
    Ted_9 Member Posts: 1,718
    my thoughts

    It looks to me like the circ will just short circuit. I dont see why the circ would pull water from the "injection" loop.

    Are there other components missing?

    Why not use a 3/4 3 way and put the cast BB on outdoor reset the way the valve was meant to work.
    You may be able to buy just the 3/4 valve body and use the head.

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  • Weezbo
    Weezbo Member Posts: 6,232
    heres the glitch in the deal.

    with the closely spaced T's you have, the water would seek the path around to the supply side of the pump...remember... whatever goes into the T must come out of the T, unless you are counting on the differential pressure of the colder return water overcomming the head like a gravity system , and the same thing on the boiler side ,which is quite a lot to consider ... you would need a few more pieces.... as Ted said earlier. mounting the sensor on the pipe feeding the system would let you know the entering temp . yet, what would increase the water temp other than pressure.... and as the two closely spaced T's is a hydraulic isolater...you would need a means (Circ on the mixer) to change that flow and temp.

    a 003 on the 1/2" would work as your injection pump however a check valve on the return to the boiler would create a desire in the return water to go through the mixer ,through the injection pump and into the system loop..first and the boiler second. then depending on the boiler or heat source you might have to control the return temps from the system loop return to the boiler...then there is a minor technicality when you get back to the boiler it will need something to get the btus out of it to the mixer and back into the return ahead of the system loop return flow...to temper the water back up ...
    because as you know the mixed supply temp and the return temps may have some wide delta t....
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