During a defrost cycle, heat pumps melt ice on the outside coil using which heat source?

• A. Electric Resistance Heater
• B. Ambient Air
• C. Hot Refrigerant From The Compressor
• D. Hot Water Circulating Through The Coil

Answer: (C)

During a defrost cycle, the heat source is hot refrigerant from the compressor. This hot gas is routed through the outdoor coil (hot-gas defrost), warming the coil surface and melting the ice quickly. This method uses the refrigerant that’s already been heated by compression, so it can melt ice even in cold outdoor conditions and then return to normal heating. Ambient air is what normally heats the outdoor coil during regular operation, not the defrost process. Hot water circulating through the coil is used in hydronic systems, and electric resistance heaters are typically only supplemental, not the primary defrost heat source.