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Thread: 3M-50 Wi-Fi Thermostat

  1. #7
    Junior Member

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    Thanks for this. How would I wire my thermostat if I want 2 stage heat but only 1 stage AC? I do not have a 2 stage AC unit but I have a 2 stage furnace.




    Update amazon now offers a free smart home consultation

    Thanks,
    Steve

    Quote Originally Posted by Thermostat View Post
    4 wire Filtrete 3m50 wiring diagram for a 1 cool 1 heat unit
    Attachment 72




  2. #8
    HVAC Thermostat Specialist

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    Your second stage heat wire would be connected to W2.

  3. #9
    Junior Member

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    Quote Originally Posted by HVAC View Post
    Your second stage heat wire would be connected to W2.
    I'm trying to determine if my thermostat was properly connected. In order for my Lennox SLP98V to run in variable speed mode, it needs to be wired in 2 stage heat mode at the thermostat.



    Here are the wires as they currently appear connected to the thermostat along with my comments / question. My AC is not a 2 stage unit, hence no Y2 wire.

    C (OK as is)
    W (OK as is)
    W2 (OK as is)
    Y (OK as is)
    RC (Not currently jumpered to RH terminal - should it be?)
    G (OK as is)

    Thanks for your help.
    Steve

  4. #10
    HVAC Thermostat Specialist

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    If your old thermostat only had one wire for R you will need a jumper between RC and RH. The 3M50 comes from the factory with a jumper wire between RH and RC terminals. You should be able to see it. The jumper is not needed on system that have separate wires landed on RC and RH. A system that has separate wires on RC and RH has two transformers. One for cooling and one for heating

  5. #11
    Junior Member

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    Quote Originally Posted by HVAC View Post
    If your old thermostat only had one wire for R you will need a jumper between RC and RH. The 3M50 comes from the factory with a jumper wire between RH and RC terminals. You should be able to see it. The jumper is not needed on system that have separate wires landed on RC and RH. A system that has separate wires on RC and RH has two transformers. One for cooling and one for heating
    Thanks - when they installed my new furnace, they removed the jumper on RH & RC. I don't know why they did that.

    How would it affect my AC or Furnace if there should be a jumper and they removed it? Would something not work right?

    Radio Thermostat CT50 7-Day Programmable Thermostat (WiFi Enabled), iOS & Android App Controls

    Thanks,
    Steve

  6. #12
    HVAC Thermostat Specialist

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    Quote Originally Posted by stevetothink View Post
    How would it affect my AC or Furnace if there should be a jumper and they removed it? Would something not work right?
    If the jumper needs to be installed and you only have a wire installed on RC your heat will not work.


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