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Mixing pumps

Has anyone had any experience with mixing circulator pumps on both the supply and return?
Reason for asking is I have an 8 iron radiator zone consisting of two floors, a indirect domestic hot water heater zone, a heat coil in an air handler zone all on individual circulators on the return manifold. I want to add two radiant floor zones to this system. I have five zone manifolds on the supply and return I set up anticipating this install later. Well later is now and doing some reading on setting up the mixing valves, I find some warnings that the pump on the return side manifold tends to pull from the cold side of the mixing valve plumed to the return side of the zone, and the proper way to plumb these mixing valves is to pump from the supply side manifold?
I'm from the school of return side circulators for heat zones. I understand the push side argument. I prefer return when possible.
I've never tried mixing supply/return circulators and was wondering if anyone has any guidance on this?


  • hot_rod
    hot_rod Member Posts: 20,725
    You need pump away from the mixed portion 3 way thermostatic valves to get proper mixing results.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream