Lennox 49L87 Limit Switch

The Lennox 49L87 Limit Switch is a critical safety component designed for precise thermal regulation in residential gas furnaces and commercial heating systems. As a genuine OEM replacement part, this normally closed (NCO) limit control is engineered to open the electrical circuit upon reaching its fixed 230°F cut-out temperature, effectively preventing heat exchanger damage and hazardous conditions. Once the system cools to the 200°F cut-in temperature, the automatic reset mechanism restores the circuit for continued operation. Featuring a 3-inch insertion length (stilt type) and a distinct red sleeve for rapid identification during field service, the 49L87 provides the exact calibration required for high-limit protection. It is frequently utilized in popular Lennox G43 and G51MP series units, as well as compatible Allied Air, Armstrong, and Ducane equipment. For HVAC contractors, using this Lennox furnace limit switch ensures factory-spec reliability and maintains the structural integrity of the high-limit safety string.

Key Benefits for Technicians:

• Direct OEM Compatibility: Replaces Lennox 49L8701 and cross-references with 36T01B3 and L230-30F to ensure a perfect fit in the mounting bracket.
• Precision Thermal Calibration: Fixed 230 degree trip point with a 30-degree differential (resets at 200°F) for accurate high-temperature limitation.
• Simplified Testing: The 3" stilt insert allows for proper probe depth within the air stream to capture accurate plenum temperatures.
• Automatic Reset Functionality: Eliminates the need for manual intervention after a temporary overheat condition, reducing nuisance service callbacks.

Common Questions:

What causes a Lennox 49L87 limit switch to trip frequently?
Frequent tripping usually indicates restricted airflow, often caused by a dirty air filter, blocked return grilles, or a failing blower motor. If the switch stays open even when cool, the internal bimetal disc may have failed, requiring a replacement.

Can I use a different insertion length if the 3-inch version is unavailable?
It is not recommended. The 3-inch insert is specifically calibrated to the furnace’s heat exchanger geometry. Using a shorter or longer probe can lead to delayed tripping or premature "nuisance" opening, compromising system safety.

How do I verify if my 49L87 limit switch is defective?
With the power off and wires disconnected, check for continuity across the terminals. Since this is a normally closed (NC) switch, it should show 0 ohms at room temperature. An "Open" reading (OL) at room temperature indicates a failed component.

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.