Lennox 18M84 Limit Switch

Professional-grade Lennox 18M84 limit switches are critical safety components designed to regulate internal furnace temperatures and protect heat exchangers from thermal stress. This OEM Lennox limit control features a 3-inch insertion depth and is factory-calibrated for an auto-reset range of 230-260°F. As a normally closed switch, it breaks the electrical circuit to the gas valve if the plenum temperature exceeds the 260°F threshold, typically caused by restricted airflow, a failing blower motor, or clogged filtration. Known by the technical designation L260-30F, this fixed-temperature limit switch ensures the system remains within safe operating parameters before automatically resetting once temperatures drop by 30 degrees. This part is a direct replacement for various G40, G43, and G61 series units, maintaining the precise HVAC safety limit specifications required for high-efficiency gas furnaces. Utilizing genuine 18M84 furnace parts ensures terminal compatibility and mechanical alignment within the combustion chamber, preventing nuisance trips and ensuring reliable heat cycle execution for residential and industrial applications.

Key Benefits

• Precise Thermal Regulation: Operates within a strict 230-260°F window to prevent heat exchanger cracking and rollout conditions.
• Automatic Reset Functionality: The L260-30F 18M84 automatically restores the circuit once the system cools, reducing manual intervention after temporary airflow blockages.
• Direct OEM Compatibility: Engineered specifically for Lennox G40DF, G43UF, and G61MP series furnaces, ensuring exact fitment of the 3-inch probe.
• Industrial-Grade Construction: Built to withstand high-cycle environments in demanding HVACR applications without calibrated drift.

Common Questions

What causes a Lennox 18M84 limit switch to trip repeatedly?
Frequent tripping usually indicates restricted airflow. Check for a dirty air filter, blocked return vents, or a failing blower motor. If the 230-260F limit switch opens, it is performing its safety function to prevent the furnace from overheating.

Is the 18M84 compatible with 24V control circuits?
Yes, this Lennox replacement part is designed to interface with standard 24V furnace control boards and gas valves, acting as a mechanical break in the safety string.

How do I verify if I need a 3-inch insert limit switch?
The insertion depth (3") is critical for accurate sensing. Measure the probe length of your existing L260-30F switch to ensure it reaches the correct position within the airflow path for an accurate temperature reading.

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.