How can you tell if a furnace is two stage?

Answered by Phillip Nicastro

To determine if a furnace is two-stage, you can look for specific wiring configurations. Two-stage conventional heating systems typically have wires leading into the W1 and W2 terminals on the furnace control board. These terminals are used to control the operation of the furnace at different stages of heating.

In a two-stage heating system, the furnace can operate at a lower stage for milder weather and switch to a higher stage for more extreme cold. This allows for more precise temperature control and improved energy efficiency.

When inspecting the furnace, you can locate the control board, which is usually found inside the furnace cabinet. On the control board, you’ll see various terminals labeled with letters indicating their function. Look for the terminals labeled W1 and W2.

If you find wires connected to both the W1 and W2 terminals, it indicates that the furnace is designed for two-stage heating. These wires are typically connected to the thermostat, which sends signals to the furnace control board to activate the appropriate heating stages.

It’s important to note that not all furnaces are two-stage, and the presence of wires connected to the W1 and W2 terminals is specific to two-stage conventional heating systems. If you don’t see any wires connected to these terminals, it suggests that the furnace is not designed for two-stage heating.

In addition to the wiring configuration, you can also check the furnace specifications or documentation provided by the manufacturer. This information usually indicates whether the furnace is single-stage or two-stage. It’s always a good idea to consult the manufacturer’s documentation for accurate and detailed information about the furnace’s capabilities.

If you’re unsure about the wiring or need further clarification, it’s recommended to consult a professional HVAC technician. They have the expertise and knowledge to accurately assess the furnace and provide you with the necessary information.

In conclusion, to determine if a furnace is two-stage, you can look for wires leading into the W1 and W2 terminals on the furnace control board. This wiring configuration indicates that the furnace is designed for two-stage conventional heating. However, it’s always best to consult the manufacturer’s documentation or seek professional assistance for accurate information about the furnace’s capabilities.