Furnace Thermostat Wiring Color Code Standard

We give a summary tables of both traditional and current thermostat wire color code keys above the 5 universal base colors for thermostat wires which are in order of frequency of use red white green yellow and black.

Furnace thermostat wiring color code standard. Choosing the proper gauge. Your best bet is to see the manufacturer s documentation both thermostat and hvac. How to wire a thermostat. The furnace controls the fan because oil and gas heat is not instantaneous.

Color of wire and termination. Multi stage systems can require up to 8 conductors because of the amount of communication needed between the thermostat and air handler or furnace. Thermostat wiring to a furnace and ac unit. And also the normal color code used.

For shorter runs use 20 gauge. Each wire connects to a different terminal and is responsible for a different function. Below is an industry standard thermostat wire color code complete with each wire s function. 18 gauge thermostat wire is recommended for any distances up to 250 feet.

It is a red wire and comes from the transformer usually located in the air handler for split systems but you may find the transformer in the condensing unit. Lack of standards makes this interesting. While there isn t an official standard for thermostat circuit wiring colors there is a general pattern. To install a new thermostat or repair an existing device you ll need to understand the different colors of wires.

Color code how it works diagram. Thermostat wiring and wire color chart thermostat wiring colors code. R the r terminal is the power. Color codes for 24v thermostat wires are divided into two groups.