Lennox 78L29 Rollout Switch

The Lennox 78L29 Rollout Switch is a critical safety component designed for high-limit thermal protection in gas-fired furnaces. This manual reset flame rollout switch is engineered to open the electrical circuit if it detects excessive heat or flame rollout conditions in the burner vestibule, preventing potential fire hazards. Rated for an actuation temperature of 250 degrees F, this SPST (Single Pole Single Throw) snap-action switch ensures precise interruption of the 24V control circuit. The Lennox 78L29 serves as a direct replacement for part number 78L2901, providing a seamless fit for technicians servicing Lennox, Armstrong, and Ducane equipment. Since a tripped rollout switch often indicates a cracked heat exchanger, soot buildup, or venting obstructions, this component is essential for diagnostic safety protocols. Professionals rely on this furnace safety limit switch for its rugged construction and reliable calibration within the combustion chamber environment.

Key Benefits for HVAC Professionals

• Direct OEM Compatibility: Serves as the identical replacement for Lennox 78L2901, ensuring electrical and mechanical alignment.
• Critical Safety Mechanism: Features a manual reset design that prevents the furnace from restarting until a technician inspects the underlying cause of the overheat.
• Precision Thermal Response: Factory-calibrated to trip at 250°F to protect sensitive internal components and the surrounding structure.
• Industry-Standard Configuration: Utilizes an SPST contact arrangement for simplified troubleshooting and wiring in standard 24V heating circuits.

Common Questions Regarding the 78L29 Rollout Switch

What causes a Lennox 78L29 rollout switch to trip?
A trip occurs when the temperature at the burner box exceeds 250 degrees F. Common causes include a blocked flue, restricted secondary heat exchanger, or a cracked primary heat exchanger causing flames to "roll out" toward the controls.

Is the 78L29 interchangeable with the 78L2901?
Yes, the 78L29 is the exact same component as the Lennox 78L2901. They are functionally and physically identical for all Lennox-family applications.

Can I bypass this switch to keep the heat running?
Never bypass a rollout switch. These are safety-critical devices. If the switch opens, the system must be inspected for combustion issues or heat exchanger failure before resetting.

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.