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Theromostat Wiring Question - Steam + Central AC

Both will work with Millivolt systems.


  • 24v AC and millivolt steam on same t-stat

    I currently have 2 thermostats (both Honeywell VisionPRO). One controls the steam heat, and the other was put in when I had central A/C installed.

    My question is can I run a 24volt and millvolt system off of the same t-stat - and how would the "R" wires get connected. Do I run the "R" from the heat to the "R" on the t-stat, and then the "R" from the A/C to the "Rc" on the t-stat and remove the jumper between R and Rc on the stat?

  • martin
    martin Member Posts: 144

    IF THE vision-pro will handle millivolt systems the wiring you described is correct. Rh & W for heat Rc, Y, & G for A?C
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