What is the Function of the Yellow Wire in a Gas Furnace?
The yellow wire in a gas furnace system is primarily associated with the cooling function, but in the context of a gas furnace, it is not directly involved. However, it is crucial to understand its role in the broader HVAC system, as it may still be present in the thermostat wiring.
The yellow wire typically connects to the compressor of the air conditioning system, controlling the cooling operation. In a gas furnace setup, this wire is not directly connected to the furnace itself but is part of the overall thermostat wiring that manages both heating and cooling functions. While the yellow wire does not directly interact with the gas furnace, it is essential for the overall HVAC system’s operation, especially in systems that include both heating and cooling capabilities.
What is the Function of the Red Wire in a Gas Furnace?
The red wire in a gas furnace system is critical for providing power to the thermostat and subsequently to the heating system.
The red wire, often labeled as Rc (cooling) or Rh (heating), serves as the power source for the thermostat. In a gas furnace setup, the Rh wire is particularly relevant as it connects to the heating relay or valve, activating the heating system when the thermostat calls for heat.
- Rc: Typically associated with cooling systems, but in dual transformer setups, it can also be relevant.
- Rh: Specifically connects to the heating system, providing the necessary power to activate the furnace.
The red wire usually carries a 24-volt power supply, which is standard for most HVAC systems. This voltage is sufficient to control the various components of the heating system without posing a significant electrical risk.
What is the Function of the Green Wire in a Gas Furnace?
The green wire in a gas furnace system is responsible for controlling the fan operation.
The green wire connects to the fan relay of the heating system, ensuring that the fan operates correctly to circulate air through the home. This wire is essential for maintaining proper air circulation and can be activated independently of the heating or cooling cycles.
The green wire connects to the terminal G on the thermostat and to the fan relay or air handler in the furnace. This connection allows the thermostat to control the fan’s operation, which is vital for efficient heating and cooling.
Summary
- Yellow Wire: Primarily associated with cooling, not directly involved with the gas furnace but part of the overall HVAC system.
- Red Wire: Provides power to the thermostat and heating system, with Rh being specific to heating.
- Green Wire: Controls the fan operation, ensuring proper air circulation.
Reference
- Horizon Services: Your Complete Guide to Thermostat Wire Colors
- The HVAC Service: Thermostat Wire Color Code: Complete Information You Need to Know
- Aire Serv: Thermostat Wire Color Codes You Need to Know
