Thermostat Wires

Thermostat wires or cables are used to connect a thermostat to the cooling, heating, and ventilating system. They are used for joining heat pumps, air conditioning controls, thermostats, heating controls and bell / alarm systems too. The thermostat wires are general purpose multi conductor low voltage control cables. They come in different varieties and are generally numbered or colored to do the correct installation.

There are various types of controls and components in a thermostat and the wires for these controls run into the thermostat. The wires are multi-colored. The controls are usually complex and in order to run properly each wire must go to the correct terminal on the thermostat otherwise it will not work properly.

Construction of thermostat cables
Thermostat cables are usually made of a solid uncovered copper conductor. Mostly copper is used in these applications. Then it is insulated with polyvinyl chloride (PVC). The insulation is done without filler and it is surrounded by a fire and sunlight resistant PVC jacket.

Sizes of thermostat wires:
The thermostat wires or cables are available in various sizes to accomplish the need of variety of uses in thermostats, air conditioners etc. The general and frequently used sizes are:

• 18/2 AWG
• 18/3 AWG
• 18/4 AWG
• 18/5 AWG
• 18/7 AWG

Coding of thermostat wires:
The thermostat wire isn't a single wire rather it is a group of wires. These wires are coded with specific letters. It isn't necessary that in all the thermostat wires the coding and coloring should be same. The different types of wires in a thermostat wire is :

• R: It is the main transformer low voltage wire. It comes off of the transformer and feeds to the thermostat.
  
  
• Y: It is the compressor wire and is connected to the other side of the compressor.
  
  
• G: It is for fan. It is connected to one side of the fan relay and there is a common wire on the other side.
  
  
• W: It is for strip heat. The strip heat has a relay and common side. The wire is connected to the other side.

Connection of thermostat cables to the system:
There are generally five terminals in a thermostat to connect to different types of thermostat wires. The thermostat wires are colored and coded with letters to identify separate wires so that proper connections can be made. The terminals in the thermostat are specified as G, Y, W, RH, B, O, and RC.

• The G terminal is connected with the green wire which at the other end is connected to the fan.
  
  
• The Y terminal is connected to the yellow wire which at the other end is joined to the cooler compressor.
  
  
• The W terminal on the thermostat is connected to the heater control line.
  
  
• The RH terminal on the thermostat is joined to the heater transformer.
  
  
• The RC terminal is connected to the thermostat wire which on other hand is connected to cooler transformer.