To use a Honeywell wiring diagram, first identify the model of Honeywell thermostat you are using by locating the model number on the Honeywell product. In a four-wire Honeywell diagram, the wire marked G indicates the green fan wire. The red wire, marked with an R on the diagram, is the 24 VAC/Rc and R or Rh. The yellow wire, marked Y, links the compressor/air conditioner, while the white wire marked W is for heat.
If the wires in the thermostat differ from those on the diagram, tag them upon removal so you remember where they belong. Match the wires with the same letters on the terminal. On a five-wire Honeywell diagram, there is an additional C wire. Common C-wire colors include purple, brown or blue. They indicate the 24 VAC Common on the diagram.
The Common wire connects to the COM 24V terminal on the diagram. If the labels don't match the letters on the thermostat, Honeywell has a chart for the proper connections. R, RH, 4 and V wires connect to the R terminal. Rc connects to the Rc terminal, while G and F wires connect to terminal G. Y, Y1 and M connect to terminal Y.
A chart on How-To-Wire-It.com lists the terminals on a wiring diagram, indicates common wire colors for those terminals and describes their locations. Depending on the model of Honeywell product, the red wire is typically connected to the RC & 4 terminals. While straight lines labeled with letters represent wires on the diagram, a series of offset dots and lines indicate the presence of safety shut-down devices. These connect to the heat exchange unit and ensure the system does not reach dangerous heat levels.