Lennox 49F59 Defrost Relay

The Lennox 49F59 Defrost Relay (also identified under part number 49F5901) is an essential OEM switching component designed for precise defrost cycle management in residential and commercial heat pump systems. As a veteran-grade SPDT and DPST relay, this unit operates within a 208-240V range at 60Hz, providing the heavy-duty electrical switching required to energize defrost heaters and manage reversing valve transitions. This part is critical for preventing evaporator coil ice buildup, ensuring the system maintains optimal airflow and heat transfer during low-ambient operations. When the outdoor fan relay or internal switching logic fails, it can mimic a motor failure; the 49F59 restores the necessary electrical continuity to keep the unit operational and prevent liquid slugging or compressor strain. Its Lennox 49F5901 compatibility makes it a direct drop-in replacement for a wide range of legacy and modern Lennox HVAC equipment, including CHP15 and various HP series units.

• Universal Compatibility: Engineering-matched to replace both 49F59 and 49F5901 part numbers without wiring modifications.
• High-Voltage Durability: Rated for 208-240 VAC applications, ensuring stable performance across fluctuating line voltages.
• Dual-Pole Versatility: Features SPDT and DPST configurations to manage both the outdoor fan motor and the defrost heater circuit simultaneously.
• Frost Prevention: Actuates the system's heating mode to effectively clear frost from the outdoor coil, maintaining system coefficient of performance (COP).

How do I know if my defrost relay has failed?
Common indicators include the outdoor fan failing to engage while the compressor runs, or the unit failing to shift into defrost mode, leading to excessive ice accumulation. Technicians should perform a continuity test across the relay contacts; the circuit should typically remain closed unless the system is actively in a defrost cycle.

Is the 49F59 interchangeable with the 49F5901?
Yes, these two part numbers refer to the same Lennox OEM defrost relay. They are identical in form, fit, and electrical specifications.

What voltage does this relay support?
This component is designed for 208/240-volt single-phase systems and is commonly used in Lennox heat pumps and air conditioners requiring terminal-based switching for defrost logic.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.