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Amazon Smart Thermostat Wiring Question

Can someone Subject Matter Expert in the room help me with the problem/issue I am currently facing? I have the Rheem AC and Heating unit upstairs. I wanted to replace the Rheem thermostat with an Amazon Smart thermostat. After installation, the AC unit doesn't work. The Amazon thermostat is functioning and the relay is switching, but the unit doesn't run/kick on. I wanted to know if the Orange and Yellow wires are connected to the correct terminal on the Amazon thermostat. The pictures show the Old and New wiring connections. Please helps. I really appreciate any help you can provide.


  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,989
    edited August 2022
    The Rheem thermostat does not have the normal wire label for conventional thermostat operation. This leads me to believe that you have a communicating thermostat, not a conventional wired thermostat. What is the model number of the air handler or furnace that the wires from the thermostat go to.

    The Rheem equipment may or may not be compatible with the Amazon Thermostat. Some equipment may be compatible however you will need to completely rewire the low voltage wires inside the condensing unit and the air handler or furnace, in order to make that happen. There could be some function loss in the Rheem equipment as a result of using the amazon thermostat. Features like variable speed control to match the load on the home as the outdoor temperature changes. This may not be a desirable outcome.
    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
    HVACNUT Member Posts: 4,870
    It would be helpful to know what the Orange and Yellow wires connect to at the air handler or furnace but I think Ed is right, you've got communicating controls. 
  • HomerJSmith
    HomerJSmith Member Posts: 1,927
    edited August 2022
    You have a multi wire cable which is nice. You may just have a wiring problem or maybe a programing problem. Can't tell without a Rheem wiring diagram with current connections at the unit.
  • ChrisJ
    ChrisJ Member Posts: 13,901
    A quick Google search shows the Rheem rhc-tst501cmms being a communicating thermostat.

    Put the Rheem thermostat back, it's likely far better than the Amazon.
    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 4,989
    @HVACNUT, the wiring diagram for the model number on the thermostat sub-base indicates that the air handler and the condensing unit both have R, W, 1, and 2 terminals. R & W are 24 volt to power each circuit board on the system. 1 & 2 are for communication on a digital basis.

    There is no common communication protocol from the different manufacturers, I used to do American Standard/Trane with A,B,C, & D. I believe Carrier/Bryant also used the same letters but they were not cross compatible.
    Edward Young Retired HVAC Contractor & HYDRONICIAN Services first oil burner at age 16 P/T trainer for EH-CC.org
  • tienchau2022
    tienchau2022 Member Posts: 2
    Thank you to all the experts that gave me the inputs/suggestion. All of your comments were correct. I have reinstalled the Rheem thermostat and everything is now back to operation. Many thanks again.
  • ratio
    ratio Member Posts: 3,336
    Looks like there is a current version of that stat, it may be compatible. It doesn't seem to be WiFi enabled, however.
    https://www.meiersupply.com/itemdetail/RUUD UHC-TST550CMMS