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  1. #1
    Join Date
    Aug 2008
    Posts
    416

    Location for Indoor Remote Temp Sensor

    OK, builder mounted my tsat in living room, interior wall BUT this wall contains supply duct to upstairs. So it short cycles, definitely in heat mode and maybe cool mode as tsat's internal sensor is affected by duct.

    Simplest solution for Trane TCONT803/Honeywell 8421 seems to be to install a remote indoor sensor (this is not heat pump with outdoor sensor).

    Question is, Where should it be mounted???

    Specifically, I had a HVAC contractor recommend placing whole tsat (or remote sensor) directly below 1st floor central RETURN. He says its a good place as it reflects indoor temp/humidity and its not a dead air spot.

    Obviously, not near supply vents, windows, sun, etc. But there is moving air.. Is that a problem??

    What do you pros think of the return air vent placement approx. 5ft above floor???

  2. #2
    Join Date
    Jul 2008
    Location
    Poestenkill, NY
    Posts
    769
    I think that is sound advice.

    Also -air movement and temp are independent factors - the T-stat feels no "wind chill factor", if that's what you are worried about.

    And if that isn't what you're worried about, I do agree that the return air "path" is OK because that does indicate space temp as good as any other location.

  3. #3
    Join Date
    May 2008
    Location
    Last moon off of Pluto
    Posts
    49
    I say relocate the whole thermostat and clean up the original location cosmetically. Putting in a temp sensor in another location can potentially confuse a service guy a few years down the road.

  4. #4
    Join Date
    Jun 2007
    Location
    south carolina
    Posts
    176
    How is the upstairs duct affecting the thermostat?

  5. #5
    Join Date
    Jan 2004
    Location
    Lancaster PA
    Posts
    68,586
    At the return is a good location.
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  6. #6
    Join Date
    Aug 2008
    Posts
    416
    "How is the upstairs duct affecting the thermostat?"

    The supply duct inside the wall is radiating heat (in heat mode) and causing the wall surface to heat up and the tstat senses this heat and shuts off when room temp is stll low. Similar thing happens on cool...

    Notice that tsat directions state not to place on wall with duct work inside... Obviously, my builders HVAC contractor didn't know or care to follow this....

    As to the location under return vent...
    Thanks for advice, for now I will relocate the temp sensor and if I like performace i will relocate the whole tstat... It would be in high traffic area and with kid's I was worried it would get a hard knock and fly off the wall....

    Currently remote sensor is 2 feet away and worked for 15 years. This was the old White Rodgers tstat with remote sensor. Just had new TCONT803 (Trane) installed and funny thing happened. Remote sensor was on backorder and was just hooked up Sat. Its just a simple thermistor, no problem. But its acting funny.

    If tstat set for 77, then unit cycles pretty much from 76.2 to 77.8 ( a 1.6 swing going .8 below setpoint... keeping house at 77

    BUT, if setpoint is 76, suddenly the swing is 74.8 to 76.3 which cools the house to 75 or so instead of 76...

    Do you pros have any experience with these Trane/Honeywell remote sensors have this non-linear operation???? Should I try another. I have checked with Fluke ohm meter and it does not match exactly the calibration table in the install instructions, but its close and does change with temp...

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