Lennox 26H78 Rollout Switch

The Lennox 26H78 Rollout Switch (catalog number 26H7801) is a critical safety component designed for furnace flame rollout protection. This OEM Lennox part is a manual reset, SPST (Single Pole Single Throw) configuration that actuates at a fixed temperature of 260 degrees F. When the switch senses excessive heat near the burner box—typically caused by a cracked heat exchanger, blocked flue, or insufficient combustion air—it breaks the 24V circuit to the gas valve, immediately halting the heating cycle to prevent hazardous conditions.

As a closed-face type limit, the 26H78 ensures high-reliability performance in Lennox G25, 80MGF, and 78RGF series units. Because this is a manual reset rollout switch, a tripped button requires a thorough inspection of the heat exchanger and venting system before restarting the unit. Integrating genuine Lennox replacement parts ensures the system maintains its original safety listings and stays compliant with manufacturer specifications. This part is a direct 1:1 replacement for the 26H7801, offering the exact mounting footprint and thermal response curve required for professional HVAC troubleshooting and repair.

Key Benefits

• OEM Compatibility: Precision-engineered for a drop-in fit on Lennox furnaces and packaged RTUs.
• High-Temperature Calibration: Factory-set to 260°F for accurate flame rollout detection.
• Manual Reset Feature: Prevents automatic restarts, forcing a technician to diagnose the root cause of the furnace rollout trip.
• Durable SPST Design: Provides a robust electrical break to safely interrupt the ignition sequence.

Common Questions

What causes a Lennox rollout switch to trip?
A trip is usually the result of "flame rollout," where flames exit the heat exchanger. Common causes include a clogged secondary heat exchanger, a failing inducer motor, or a blocked exhaust vent.

Can I test the 26H78 for continuity?
Yes. With the power off and wires disconnected, use a multimeter to check for continuity across the terminals. If the switch is reset but shows an open circuit (no continuity), it has failed and must be replaced.

Is the 26H78 the same as the 26H7801?
Yes, these part numbers are identical and interchangeable within Lennox technical literature and parts catalogs.

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.