How to Wire a Honeywell Thermostat

By Dave Rongey - Summary:

Wiring Instruction Guide for a Honeywell Heating Thermostat: Typical Thermostat Wiring for Furnace Heating and Air Conditioning.

Wiring Guide for a Honeywell Thermostat

Electrical Question: I bought a Honeywell Heating thermostat. There were no directions about how to wire it.

  • How come there were no wires coming out of the back of the thermostat?
  • I need to know where to connect the thermostat wires from the wall.
  • This is a round thermostat with a dial on it.

This electrical wiring question came from: Pamela, a Handy woman from Brockton, Ma.
Additional Comments: Great!

Dave’s Reply:
Thanks for your electrical wiring question Pamela.

Wiring Instructions for a Honeywell Heating Thermostat

Skill Level: Beginner to Intermediate.
Tools Required: Basic Electricians Pouch Hand Tools.
Estimated Time: Depends on personal level experience and ability to work with tools.
Precaution: Identify the furnace or air conditioning circuit, turn it OFF and  Tag it with a Note before working with the wiring.

  • The model number of the Honeywell thermostat was not provided, however here are the typical wiring assignments for a conventional heating system.
  • Keep in mind that there should be a low voltage cable in the wall where the thermostat is located which has individual wires as shown in the instructions below.

Typical Thermostat Wiring for Furnace Heating and Air Conditioning

Terminal  Label –    Wire Color  –   Function /Description

  • R   –  Red Wire  –   24 Volts.
  • B   –   Blue Wire  –   Cooling.
  • G    –  Green Wire or Grey Wire *  –   Fan Blower.
  • W   –  White White  –   Heating.

Although many home heating and air conditioning systems have a standard type thermostat cable with color coded wires, the wires should be identified to make sure of the exact purpose for each wire.

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FAQs Frequently Asked Questions and Comments

3 Responses to “How to Wire a Honeywell Thermostat”
  1. Don says:

    A simple electronic schematic for a heat cool thermostat would be nice.

  2. ALLAN HURST says:


    • Dave Rongey says:

      Hi Allen,
      If the fan is working from the manual fan switch on the thermostat then one of the components of the heating system may be faulty. There are several events that must take place before the control board will allow the heating process to begin. Each of the components are monitored by sensors, such as the exhaust discharge fan, and limit switches. If any one of these components or sensors are not working properly, or if the main control board is faulty then the heating cycle will not be triggered to start. This problem will require specific testing and troubleshooting of your furnace to locate the problem and then make the necessary repairs.
      I hope this helps,


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