Lennox 78F91 Motor

The Lennox 78F91 is a direct-drive, multi-speed blower motor engineered for consistent performance in residential and light commercial air handlers and furnaces. Operating at 208-230V 1-phase power, this 1/2 HP motor delivers a rated speed of 1075 RPM. As a 3-speed HVAC motor, it allows for precise airflow adjustment to meet specific static pressure requirements, ensuring optimal heat exchange across the evaporator or heat exchanger. This motor features an Open Air Over (OAO) enclosure, designed to utilize the system's airflow for thermal management, which prevents overheating during continuous duty cycles. It typically requires a 10MFD/370V run capacitor for proper phase torque and efficiency. When replacing an OEM 78F91 furnace motor, verify the frame size and shaft dimensions to ensure mechanical alignment with the blower wheel. This robust induction motor is a standard service part for maintaining the Lennox system airflow integrity and restoring factory-spec static pressure performance.

• Multi-Speed Versatility: Three distinct speed taps allow for customized CFM delivery based on ductwork resistance.
• OEM Compatibility: Precision-engineered as a direct replacement for Lennox and Allied Air equipment to maintain system UL listing.
• Optimized Efficiency: Standard PSC design provides a reliable balance between amperage draw and high-starting torque.
• Resilient Construction: Designed with high-grade internal windings and bearings for extended lifecycle in high-cycling environments.

Common Installation Questions

What capacitor does the Lennox 78F91 require?
This motor is designed to operate with a 10 MFD at 370V run capacitor. Using an incorrectly rated capacitor can lead to winding failure or increased amperage draw.

Can this motor be used in 115V applications?
No, the 78F91 is rated strictly for 208-230V single-phase power. Applying 115V will prevent the motor from reaching rated RPM and will likely damage the internal components.

How do I identify the speed taps on this motor?
Standard HVAC lead coloring usually applies, but you should always reference the schematic on the motor housing label for high, medium, and low speed wiring before energizing the circuit.

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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.