Air-source heat pump outdoor unit beside a house in the snow
Generic photo: PeterEastern · CC BY-SA 4.0

Dual fuel (heat pump + gas furnace): changeover and balance point settings

In a dual fuel system the heat pump should heat down to a chosen outdoor temperature, then stop while the furnace takes over. The two should not heat together except during defrost, when the furnace tempers the air. Problems are almost always setup: wrong backup heat type in the thermostat, no outdoor temperature source, or a thermostat that does not support dual fuel at all.

Cross-checked ~45 min moderateBrands: All

Before you start

  • Gas valve, burner and venting work are BLOCKED: refer to a licensed gas technician
  • Refrigerant work is BLOCKED (EPA 608)
  • Furnace and outdoor unit have line voltage: CAUTION

Diagnostic steps

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