Goodman Furnace: Fossil fuel application with a heat pump

Fossil fuel application with a heat pump on a Goodman furnace: This furnace can pair with a heat pump as a fossil fuel system, where an outdoor temperature sensor decides whether the heat pump or the gas furnace does the work. The heat pump gets priority unless a compressor or backup heat balance point lockout is active. The control adjusts stage times after the first call. If the heat pump cannot satisfy the thermostat in the target runtime, it is locked out until the furnace can do so on low stage. It is a hybrid or dual fuel setup, and it saves on fuel cost when gas is cheaper than electricity at low outdoor temperatures.

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Applies to: Furnaces paired with a heat pump in fossil fuel mode

Common causes of fossil fuel application with a heat pump

• Dual fuel or hybrid install with a heat pump and gas furnace
• Heat pump not keeping up at low outdoor temperatures
• Non-communicating single stage heat pump needing extra control hardware
• Wiring mixed between the furnace control and the fossil fuel board

How to fix fossil fuel application with a heat pump: step by step

1. On non-communicating single stage heat pump systems, use a fossil fuel kit and follow its wiring guide.
2. Connect all furnace wiring to the furnace integrated control module and to the FURNACE terminal strip on the fossil fuel control board.
3. Turn power off before wiring, and confirm 24 V low voltage connections are made to the correct terminals.
4. Confirm the outdoor temperature sensor reads correctly.
5. Test heat pump and furnace operation separately and check changeover.

If the unit shows an error code, look it up: Goodman Furnace codes