2 to 8 Wire All Thermostats Wiring Diagrams (Honeywell, Nest)
Hey, in this article, we are going to see the wiring diagram of different types of thermostats such as 2-wire, 3-wire, 4-wire, and up to 8-wire. These wiring diagrams will help you to make connections for thermostats from any brand like Honeywell, Nest, Sensi, Trane, Carrier, Goodman, White Rodgers, or Ecobee, etc. No matter from which brand you have the thermostat. You will learn how to wire any thermostat. Here, you will get knowledge about their color coding also.
Thermostats are devices used to regulate temperature in various systems, such as HVAC (heating, ventilation, and air conditioning) systems. Thermostats are devices used to regulate temperature in various systems, such as HVAC (heating, ventilation, and air conditioning) systems. There are different types of thermostats based on operating voltage such as -
24V Thermostats: These are commonly used in low-voltage HVAC systems. They're found in residential settings and control heating and cooling systems like furnaces, heat pumps, and air conditioners. The 24V is considered a safe and standard voltage for household applications.
110V or 240V Thermostats: These higher voltage thermostats are typically used for controlling electric heating systems. Electric baseboard heaters, wall heaters, and radiant heating systems often operate at 110V or 240V. These thermostats are designed to handle higher power loads associated with electric heating elements.
Millivolt (mV) Thermostats: Millivolt thermostats are used in systems that generate a small voltage, typically in the range of a few millivolts. These are often used with gas-fired heating systems, such as fireplaces and certain types of wall heaters. They generate power from the thermocouple or thermopile, which is a temperature-sensing component that generates a small voltage when exposed to heat.
Thermostat Terminals and Their Color Codes
Thermostat terminals and their colors can vary depending on the type of HVAC system you have and the specific thermostat model you're using. However, here, I have given a general overview of common thermostat terminals, their typical colors, and their functions in a standard heating and cooling system that are followed by almost all the popular brands. Keep in mind that this is a general guide, and it is always recommended that you should refer to your specific thermostat's manual for accurate information.
The below terminals are described as Terminal Name or Labels - Wire Colors - Wiring Functions
Y - Yellow - Cooling: Controls the cooling system; sends a signal to activate air conditioning.
Y2 - Light Blue/Other Colors - 2-Stage Cooling: Manages second-stage cooling in systems with dual cooling stages.
W - White - Heating: Controls the heating system, activating the furnace or heating source.
W2 - Brown/Other Colors - 2-Stage Heating: Handles second-stage heating in systems with dual heating stages.
G - Green - Indoor Fan/Air Handler: Controls the indoor fan or air handler to circulate air through the HVAC system.
C - Blue/Black - Common Wire: Provides a common return path for the 24V power supply, enhancing thermostat functionality.
R - Red - 24V Power: Receives 24V power supply from the HVAC system's transformer, powering the thermostat.
RC - Red - 24V Power: Another terminal for 24V power, often used for separate heating and cooling systems.
E - No Universal Color - Emergency Heating: Activates the emergency heating source when primary heating fails.
X/AUX - No Universal Color - Auxiliary Heating: Controls auxiliary or additional heating sources, often used in heat pump systems.
B - Dark Blue - Reverse Valve For Heating: Manages the reverse valve's action for heating in heat pump systems.
O - Orange - Reverse Valve For Cooling: Controls the reverse valve's action for cooling in heat pump systems.
S1/S2 - No Universal Color - For Outdoor Unit: Used to connect outdoor unit components, often related to multi-stage systems or advanced features.
2-Wire Thermostat Wiring Diagram
A two-wire thermostat is commonly used in systems where only heating is needed, and there is no need for a cooling function. These types of thermostats are typically found in simpler heating systems.
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Connection Procedure
- Connect the Red wire to the R terminal for 24V Power supply or to the RC terminal if that is where it was on the old thermostat. If Both R and RC terminals are available then connect them with a jumper wire.
- Connect the White wire to the W terminal for Heating.
3-Wire Thermostat Wiring Diagram
A 3-wire thermostat is commonly used in heating systems where there's a need for both heating and cooling control but without multi-stage systems.
Connection Procedure
- Connect the Red wire to the R terminal for 24V Power supply or to the RC terminal if that is where it was on the old thermostat. If Both R and RC terminals are available then connect them with a jumper wire.
- Connect the White wire to the W terminal for Heating.
- Old model, 3-wire thermostats have G terminal. In this case, connect the green wire to the G terminal to power the fan or air handler.
- New Model, 3-wire thermostats have C terminal. In this case, you can connect the black or green wire to the C terminal to power the fan, air handler, or as a common wire.
4-Wire Thermostat Wiring Diagram
A 4-wire thermostat is a step up from a 3-wire thermostat and is suitable for slightly more complex heating and cooling systems. It gives you a heating, cooling, and fan control system.
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Connection Procedure
- Connect the Red wire to the R terminal for 24V Power supply or to the RC terminal if that is where it was on the old thermostat. If Both R and RC terminals are available then connect them with a jumper wire.
- Connect the White wire to the W terminal for Heating.
- Connect the Yellow wire to the Y terminal for AC/cooling mode.
- Connect the Green wire to the G terminal for the Fan.
5-Wire Thermostat Wiring Diagram
A 5-wire thermostat is more versatile than its 3- or 4-wire counterparts and is often used in more complex heating and cooling systems. It provides greater flexibility for controlling various HVAC system components such as ACs, heat pumps, furnaces, and more.
Connection Procedure
- Connect the Red wire to the R terminal for 24V Power supply or to the RC terminal if that is where it was on the old thermostat. If Both R and RC terminals are available then connect them with a jumper wire.
- Connect the White wire to the W or W1 terminal for Heating.
- Connect the Yellow wire to the Y terminal for AC/cooling mode.
- Connect the Green wire to the G terminal for the Fan.
- Connect the Black or Blue wire to the C terminal for Common Wire.
6-Wire Thermostat Wiring Diagram
A 6-wire thermostat can handle complex heat pump systems with multiple stages of heating and cooling, auxiliary heat, and variable fan speeds. Here, you can see we have used the Honeywell RTH6580WF WiFi Thermostat.
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Connection Procedure
- Connect the Red wire to the R terminal for 24V Power supply or to the RC terminal if that is where it was on the old thermostat. If Both R and RC terminals are available then connect them with a jumper wire.
- Connect the White wire to the W or W1 terminal for Heating.
- Connect the Yellow wire to the Y terminal for AC/cooling mode.
- Connect the Green wire to the G terminal for the Fan.
- Connect the Black or Blue wire to the C terminal for Common Wire.
- If you have a single-stage heat pump with an Auxiliary heat strip in the air handler then connect a Light Blue wire to the X/Aux terminal for Auxiliary heat. Or, If the heat pump has two-stage cooling, connect the Light Blue wire to the Y2 terminal for 2 Stage Cooling. Or, If the heat pump has two-stage heating, connect the Brown wire to the W2 terminal for 2 Stage Heating.
7-Wire Thermostat Wiring Diagram
The 7-Wire Thermostat can be used with any type of system such as - A heat pump with 2 stages of heating and cooling, a system with Aux heating, or one that has a reversing valve that needs to be energized. We have already shown the connection for Aux heating, 2-stage heating, and cooling in the above figure.05. So, in the below wiring diagram, we have shown the connection for reversing valve.
Connection Procedure
- Connect the Red wire to the R terminal for 24V Power supply or to the RC terminal if that is where it was on the old thermostat. If Both R and RC terminals are available then connect them with a jumper wire.
- Connect the White wire to the W or W1 terminal for Heating.
- Connect the Yellow wire to the Y terminal for AC/cooling mode.
- Connect the Green wire to the G terminal for the Fan.
- Connect the Black or Blue wire to the C terminal for Common Wire.
- Connect the Light Blue wire to the X/Aux terminal for Auxiliary heat.
- Connect the Dark Blue wire to the B terminal for Reversing Valve for Heating. Or, connect the Orange wire to the O terminal for Reversing Valve for Cooling.
8-Wire Thermostat Wiring Diagram
The 7-Wire Thermostat gives you either connection for Reversing Valve for Heating or the connection for Reversing Valve for Cooling. But the 8-Wire Thermostat gives you both connections together.
Connection Procedure
- Connect the Red wire to the R terminal for 24V Power supply or to the RC terminal if that is where it was on the old thermostat. If Both R and RC terminals are available then connect them with a jumper wire.
- Connect the White wire to the W or W1 terminal for Heating.
- Connect the Yellow wire to the Y terminal for AC/cooling mode.
- Connect the Green wire to the G terminal for the Fan.
- Connect the Black or Blue wire to the C terminal for Common Wire.
- Connect the Light Blue wire to the X/Aux terminal for Auxiliary heat.
- Connect the Dark Blue wire to the B terminal for Reversing Valve for Heating.
- Connect the Orange wire to the O terminal for Reversing Valve for Cooling.
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2 to 8 Wire All Thermostats Wiring Diagrams (Honeywell, Nest)
Reviewed by Author
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August 31, 2023
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Reviewed by Author
on
August 31, 2023
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