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Radiant 3-way Mixing Valve Return Inlet Temp?
I am installing a couple of low-temp radiant zones, and was planning to use a 3-way mixing valve to temper down the supply to my desired temp. The valves I purchased are Taco 5000-HX's. They seem widely used for this purpose, and the manufacturers website even specifies "an ideal choice for a radiant heating system, whether in slab, over pours, or in joist bay heating installations."
Looking at the Instruction Sheet provided with the valves, I noticed they specify a "cold water inlet temperature between 39º-80ºF." Maybe I am mis-understanding, but if I have the valve outlet set at 120º for my radiant, with a 10-15º ∆T, won't the return water temp be 105º+ and way out of spec? I realize these valves are also used for tempering down domestic hot water, so maybe this specification doesn't apply to radiant? Will the valve still function as intended?
It also specifies a "Minimum Temperature Differential (between hot supply and outlet) of 10ºF." So should I assume that the valve will not function properly if set to 120º but my incoming water temp is below 130º?
Thanks in advance,