Lennox 33J84 Limit Switch

The Lennox 33J84 Limit Switch is a critical safety component designed for precise thermal regulation within residential and commercial HVAC units. Engineered as a 100-190F AUTO limit switch, this Lennox replacement part features a fixed temperature setting that triggers a circuit break at 190°F and automatically resets once the plenum temperature cools to 100°F. This furnace limit switch ensures the heat exchanger does not exceed safe operating parameters, preventing equipment damage and hazardous conditions. Its L190-90 setpoint is calibrated for high-limit protection in specific Lennox burner assemblies and air handlers. For technicians performing HVAC troubleshooting, the 33J84 offers a reliable direct OEM replacement to restore system sequence of operation. Its robust construction resists vibration and thermal cycling fatigue, ensuring long-term HVAC safety switch performance in high-demand environments. Verify the specific temperature rise and airflow requirements of your cabinet before installation to ensure these furnace thermal limit specs align with the original equipment manufacturer data.

• Broad Compatibility: Functions as a direct cross-reference for multiple Lennox furnace parts, reducing inventory complexity.
• Automatic Reset Functionality: Eliminates the need for manual intervention once the system returns to safe 100-190 degree operating ranges.
• High-Accuracy Calibration: Maintains a tight tolerance on the high-limit cutout to prevent nuisance tripping while ensuring maximum safety.
• Durable Construction: Specifically designed to withstand the high-temperature environment of the furnace heat exchanger.

What is the reset differential for this switch?
The Lennox 33J84 features a 90-degree differential, opening at 190°F and automatically resetting at 100°F to ensure the system is sufficiently cooled before the heating cycle resumes.

Can this be used in other brands besides Lennox?
While designed primarily for Lennox HVAC equipment, it can be used in other applications requiring a 190-degree high limit, provided the mounting footprint and terminal connections match the 1/4" quick-connect standards.

Why is my limit switch tripping frequently?
Frequent tripping usually indicates restricted airflow, such as a clogged filter, blocked return, or a failing blower motor, rather than a faulty Lennox 33J84 switch itself. Always verify static pressure and temperature rise during service.

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.