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NEST Thermostat Calibration

Alan (California Radiant) Forbes
Alan (California Radiant) Forbes Member Posts: 4,207
in THE MAIN WALL
We recently installed a NEST thermostat and the owners said that the room felt colder than what the thermostat showed. I checked it out and sure enough, the NEST was reading 74° and my meter said it was 70.5°. Does anyone know if these thermostats can be calibrated?
8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

Two btu per sq ft for degree difference for a slab

Comments

  • hot_rod
    hot_rod Member Posts: 23,054
    Don't know about calibration but we did have a case where a contractor put the pull down resistor behind a thermostat, instead at the relay box connection and the heat it created caused false readings.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Abracadabra
    Abracadabra Member Posts: 1,948
    this is a huge complaint of most nest owners.
    is RC and RH jumpered? protective cover on the bottom has been removed?
    try 3 things:
    1 - check voltage being supplied
    2 - restart the Nest. Settings -> Reset -> Restart
    3 - factory reset it
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,207
    Thanks, guys!
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
    zvalve
  • Rich Swatton_2
    Rich Swatton_2 Member Posts: 24
    Questin, nest advertised you only need 2 wires (no common) is this true?

    There was an error rendering this rich post.

  • Jamie Hall
    Jamie Hall Member Posts: 24,516
    Rich Swatton said:

    Questin, nest advertised you only need 2 wires (no common) is this true?

    Only under certain very limited conditions. What we've had reported here on the wall is that they aren't reliable without the third wire on most systems.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • hot_rod
    hot_rod Member Posts: 23,054
    Rich Swatton said:

    Questin, nest advertised you only need 2 wires (no common) is this true?

    Rich Swatton said:

    Questin, nest advertised you only need 2 wires (no common) is this true?


    If you have the patience and the time to wait on the NEST support line, and hopefully get to a knowledgable tech I think you will find they agree that 2 wires just won't cut it.

    With any power stealing thermostat they often "leak" current back.

    We have measured some HW stats reading 14V back at the relay when they were in the off mode!
    Most relays will interpret that as a heat call, or possible cause a relay to chatter.
    The 3rd wire provides a path for that errant current back to the board without causing a problem.

    The other fix is to install a pull down resistor to turn the stray current into heat basically :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • jimma01
    jimma01 Member Posts: 2
    I have three NESTs on on my three zone oil fired HW boiler system . Just two wires to each stat. The oldest one is three years old. I find that on a simple system like this the two wire works fine. As for temp, one of the three reads a degree low. The other two agree and and agree with my room thermometer . Nest support is pretty good . While I don't believe it's adjustable, they may make good on it and give you a replacement particularly for 4 degree difference

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