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Installation of Honeywell Home Smart Thermostat

vachi
vachi Member Posts: 1
edited March 29 in Thermostats and Controls

Hi,
New to this forum, so thank you in advance. I have a Trane XV90 furnace and I'm trying to replace my old Trane thermostat with a Honeywell Smart thermostat. I made all the connections at the thermostat, including the blue common wire, which was not used on the old thermostat. With all wires, red, green, white, blue, yellow properly seated and the circuit breakers back on for the furnace and A/C, there was no power to the thermostat. I'm wondering if the wiring needs to be reconfigured at the furnace. Any ideas? I can post the furnace configuration if needed.

Comments

  • Big Ed_4
    Big Ed_4 Member Posts: 3,149

    You need to connect the Blue or the common to the common at the unit . Now before you do . Make sure the transformer is fused …

    There was an error rendering this rich post.

    EdTheHeaterMan
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 10,337
    edited March 30

    If the blue wire was not used on the thermostat, then it may not be connected to the C on the furnace. Both ends of that blue wire must be connected for that wire to be useful. If you are using the RTH9585WF thermostat, then the R to RC jumper must be in place for most cases using the Trane XV90 series of furnaces.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    PC7060
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 10,337
    edited 12:56AM

    From photos sent to me by PM, it appears the blue wire is connected to Y on the furnace and therefore must be connected to Y on the Trane thermostat. I don't believe that the Blue wire is available to be connected to C on either the thermostat or the furnace. the Blue wire is identifying as a Yellow wire in this system.

    Screenshot 2025-03-31 at 8.07.20 PM.jpg

    See the left Existing photo has no yellow wire and the Blue is connected to the screw that is marked Y (tough to see in the photo but it was verified by vachi , The other screw terminal is supposed to be the Y1/Lo and on Trane equipment is sometimes used as the Y out to the condensing unit. But that is beside the point.

    If there is in fact an additional wire that i don't see, then I proposed the wiring on the right photo that I modified. If there is no extra wire then vachi needs to run another 5 wire to the thermostat or decide if they want to try their hand at this product called Add A Wire ™

    Hope this helps.

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    PC7060

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