Thermostat Wiring Colors Code | HVAC Control

by | Thermostats | 108 comments

Thermostat Wiring Colors Code Page Navigation

    1. Essential Thermostat Wiring Color Guide Including Manufacturers Instructions
    2. Thermostat Terminal Designations Quick Guide - Detail Wiring Color Guide Below
      • Red-Wire - connects to the R terminal with the red wire
      • RC-Wire - connects to the RC terminal RC red
      • RH-Wire - connects to RH terminal RH heat
      • Y-Wire - connects to the Y terminal and is for cooling stage 1 with the yellow wire
      • Y2-Wire - connects to Y2 terminal and is for cooling stage 2
      • W-Wire - connects to W terminal and for heat stage 1 with the white wire
      • W2-Wire - connects to W2 terminal and for heat stage 2
      • G-Wire - connects to G terminal and for fan operation with the green wire
      • C-Wire - connects to C terminal (common 24v power) with the C wire
      • O or B-Wire - connects to O or B terminal and is for reversing valve operation
      • E-Wire - connects to E terminal and is for Emergency heat
      • X or Aux-Wire - connects to X terminal and is for auxiliary
      • S1 and S2 Wires - connects to S1/S2 terminals and is for outdoor temperature sensor
    3. Thermostat Wire Color Code Chart
    4. Tracing the Wire to the Source
    5. Additional Resources

    What you will learn in the Thermostat Wiring Colors Code article:

    1. First, what thermostat wire colors is likely to go to which terminal on the thermostat in your heating and cooling system
    2. Secondly, the function of each wire terminal on the average thermostat highlighting some of the differences in those HVAC system functions from manufacturer to manufacturer as recommended for thermostat wire color
Sometimes, the thermostat is not the problem. Please check this article for a checklist of things to check before calling a heating and cooling repair service.

Thermostat Wiring Colors Code | HVAC Control


Thermostat Wiring Colors CodeAlways follow the thermostat manufacturer’s instructions whenever changing the thermostat. Always turn the power off at the air handler and the condenser and make sure there is no voltage at the transformer before proceeding.

  • Furthermore, the thermostat wire colors below are the most likely colors used for most installations; however, your thermostat wire colors may be different than what the indication is here. There is no official standard for thermostat wire colors. Additionally, thermostat wiring colors are not standardized. However, these are the most wiring methods used based on my years of experience in the HVAC field, where I successfully wired a lot of thermostats and as recommended by manufacturers and common sense for thermostat wiring colors code.

    For instructions on how to wire a thermostat, please see how to wire a thermostat page. Refer back to this page for thermostat wire colors.

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