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Mixing valve issues..

Alfredjb Member Posts: 1
edited January 14 in Radiant Heating
I just installed two radiant heating zones of Navien boiler with two,  Heathguard110 HXLF series mixing valves. They have an adjustable outlet temperature range of 85 to 176 Fahrenheit, I have pure cold water going into the cool side of the mixing valve I have 180 on the boiler side and I can not get The 85 Fahrenheit setting, The temperature is always up around 120 to 140, this is for a wood floor so I must achieve 85 to 90°F for the heat temperature, I have cleaned the strainers, I am looking for an answer as to why I cannot achieve a low temperature, thank you…


  • Rich_49
    Rich_49 Member Posts: 2,663
    edited January 15
    Supply water temps in the range you describe are usually not an issue . Your " floor surface temperatures " should not go above 85* . You may be worried about nothing
    You didn't get what you didn't pay for and it will never be what you thought it would .
    Langans Plumbing & Heating LLC
    Serving most of New Jersey, Eastern Pa .
    Consultation, Design & Installation anywhere
    Rich McGrath 732-581-3833
  • EternalNoob
    EternalNoob Member Posts: 23
    rich_49 is right, supply temp of 120F is fine for a wood floor. But to answer your question more specifically, i don't see how you have "pure cold" on the cold side. Typical use of a mixing valve in a radiant zone is to mix the radiant return water as your "cold" side, which will always be warmer than "cold" water, typically in the range of 75 to 100F. If your return temp is higher than 85F then you are asking your mixing valve to do something that is not physically possible.
  • Dave H_2
    Dave H_2 Member Posts: 491
    This is proper way to pipe in a mixing valve for radiant floor applications,

    It is a closed loop system, meaning you do not pipe the mixing valve like a tempering system for a domestic water scenario like this,

    Same looking device, different applications

    Dave H
    Dave H