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TRV and Setback Thermostats

TRVs measure air temperature and open the valve proportional to the difference between where they are set and what the measured air temperature is.

They don't care about or measure the water temperature.

Danfoss provides a table for their TRVs that shows what air temp corresponds to each number on the unit.



  • Uni R
    Uni R Member Posts: 663
    TRVs and Setback Thermometers

    OK - So what happens on a two pipe or monoflow system if a bunch of the rads have TRVs and you use a setback thermometer? Do all TRVs set themselves to a particular temperature or is it a relative temperature to that of the water? The ones that are scaled on the side and not shown in degrees make me wonder whether of not they are actually set to a given temperature.
  • Unknown
    It's a given temperature

    But since they don't know if the radiator is on the ceiling or the floor, the degrees aren't printed on them.

    They are thermostats, though. Not water temperature related.

  • Mike T., Swampeast MO
    Mike T., Swampeast MO Member Posts: 6,928

    If you've set up a system with TRVs and a "master" thermostat:

    1) If you have TRVs on EVERY radiator you would generally keep the thermostat set quite high so that you are certain all of the TRVs will be satisfied. The thermostat is though useful for whole-house setback. Set the t-stat BELOW the setting of the TRVs and you essentially "starve" the TRVs. They will be wide open, but since the flow of water & BTUs is now controlled by the t-stat they cannot heat the individual spaces to the setting on the TRV. You'll get a VERY good idea of the true balance of the system.

    2) If you have a TRV on every radiator EXCEPT the one in the space with the t-stat, it's good to have that space a bit under-radiated compared to the rest of the structure. This allows the TRVs to be satisfied most of the time and allows a bit more "upward" adjustment with individual TRVs.

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