Thursday, January 13, 2011

Replacing a Thermostat, Meanings of the Different Wire Colors

Inside of the thermostat there are various terminals which should hook up with the correct wires. The R-terminal is the thermostat's energy. R usually means Red, your Denver Heating and Air Conditioning repairman ought to have red wires going to this terminal. This energy comes from the transformer. Mainly because they are supplying power, it is a superior notion to kill the power to both the condenser and the air handler before working on the thermostat.

The RC terminal is the power for cooling. In such a situation, the energy from the ac program goes to the thermostat terminal. A jumper can be installed in between RC and RH for a single transformer heating and cooling system. The RC terminal is also red.

This is also red and can be jumped to the RC.

The Y terminal is yellow and goes to the compressor relay. Some Denver HVAC specialists use a terminal board strip on the air handler control board which makes splices not required. Y2 is commonly light blue and is the code for a second stage cooler. W is the heating terminal. W is for white terminal. This ought to go straight to your heating source, whether it be a furnace or boiler. W2 is for second stage heat and is commonly brown. This is for gas furnaces with low and high settings. Heat pumps use W2 for auxiliary heat.

G is for green and goes to the indoor blower fan relay.

C is for Prevalent, and does not have a particular color while black is observed often. For digital thermostats that consume energy, the typical wire is essential to complete the 24 volt circuit.

Trane, Lennox, Goodman, Ducane, Heil, Carrier, Fedders, Amana, and Janitrol are usually hooked up to the O terminal by HVAC contractors in Denver.

S1 and S2 are for outdoor air sensors. This has no regular color, but must use a shielded wire to minimize interference and the possibility of water harm from outside. Warning: These colors are the defaults. The person wiring the thermostat could have put to use unconventional color coding.


  1. Such useful information, and thank your for the color-coded illustration to further make your point. Great post. Boca Raton AC Repair Boca Air Conditioning

  2. This is a very useful info you shared here about thermostats. Trane thermostats are also good, and I'm saying this after using the thermostat of this company.

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