Rheem Furnace Code DF
Status
Defrost mode on a dual-fuel (heat pump plus gas furnace) system. The heat pump is running a defrost cycle and the furnace is firing at fixed low-stage heat to temper the air.
Manual wording: “DEFROST MODE ... This code indicates that the heat-pump is in defrost mode (dual-fuel systems only) and furance is operating for defrost operation which is fixed at low-stage gas heating operation.”
Documented for: (-)97V, (-)96V dual-fuel installations
Likely causes, most common first
- Normal heat-pump defrost cycle on a dual-fuel system
What you can safely check yourself
- Nothing to do. Steam coming off the outdoor unit during defrost is normal.
When to call a technician
If the outdoor unit stays iced over after defrost cycles, a technician should check the heat pump.
A Rheem furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.
Sources
- Installation Instructions for Upflow Condensing Modulating, Communicating Gas Furnaces - (-)97V Series (92-24161-126-04) (Rheem Manufacturing Company, R97V series modulating condensing gas furnace (and R98V); TABLE 18 normal operation codes, TABLE 19 fault codes, pages 94-104) · checked 2026-08-25
- Installation Instructions for 4 Position Condensing Two-Stage, Communicating Gas Furnaces - (-)96V Series (92-24161-124-08) (Rheem Manufacturing Company, R96V series and (-)(-)96MDV two-stage condensing gas furnaces; TABLE 19 normal operation codes, TABLE 20 fault codes, pages 111-120) · checked 2026-08-25