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Why must a mixing valve be installed

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stevel87125
stevel87125 Member Posts: 7
edited October 2023 in Oil Heating
below the coil in a tankless coil boiler vs above the coil?

Comments

  • GGross
    GGross Member Posts: 1,720
    edited October 2023
    because the temperature held in the heat exchanger could be high enough to create extreme temperatures on the DHW side.

    For example I have seen first hand a mod/con combi boiler that was set up to heat baseboard high temp, when it would switch to DHW the boiler fluid was hot enough that we measured over 140 at the tap for a period of time
    Mad Dog_2
  • pedmec
    pedmec Member Posts: 1,238
    to prevent scalding of the people using the hot water
  • stevel87125
    stevel87125 Member Posts: 7
    I should say, why below vs above the coil
  • bburd
    bburd Member Posts: 1,231
    stevel87125 said:
    I should say, why below vs above the coil
    Because below the coil, the mixing valve and connecting piping will stay cooler than above, since heat rises.
    —
    Bburd
  • stevel87125
    stevel87125 Member Posts: 7
    Could the heat build up in an above the coil installation, that it becomes too hot for DHW, even for an instant?
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 19,398
    I don't know the exact reason. But that is what the installation instructions say. I was told installing it below the coil makes the thermostatic element last longer.
    bburd
  • mikeymo
    mikeymo Member Posts: 4
    Should you put a one way valve below the DHW and before the mixing valve?

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