Lennox 27K12 Limit Switch

The Lennox 27K12 Limit Switch is a critical safety component designed for precise thermal regulation within various residential furnace and HVAC systems. Engineering as a normally closed (NC) switch, this automatic reset limit switch is tasked with monitoring heat exchanger temperatures to prevent hazardous overheating conditions. It features a specific 3-inch insertion depth, allowing for accurate probe placement within the supply plenum air stream.

Operating with a fixed set point, this high limit control is calibrated to open the circuit on a temperature rise at 235°F, effectively cutting power to the gas valve or heating elements. Once the system cools to 205°F, the switch automatically resets, restoring the circuit for the next heating cycle. This OEM replacement part (also referenced as 27K1201) maintains compatibility with a wide range of Lennox G24M and 80MGF series units, as well as select Allied, Armstrong, and Ducane equipment. For service professionals, the Lennox 27K12 provides a reliable solution for resolving furnace short cycling and limit switch error codes caused by restricted airflow or thermal stress.

• Precise Thermal Protection: Strictly maintains safe operating limits with high-accuracy calibration at 235°F.
• OEM Compatibility: Exact drop-in replacement for Lennox 27K1201, ensuring proper fit and terminal alignment.
• Automatic Reset Logic: Eliminates the need for manual intervention, resetting the circuit once temperatures drop to 205°F.
• Durable 3-Inch Probe: Optimized insertion length for responsive temperature sensing in standard plenum configurations.

• What causes this limit switch to trip frequently? Frequent tripping is often a symptom of restricted airflow, typically due to a dirty air filter, blocked return ducts, or a failing blower motor.
• Can I use this switch in both gas and electric furnaces? Yes, the Lennox 27K12 is designed to regulate temperature in various heating applications as long as the 235°F limit and 3-inch probe specifications match the original equipment.
• How do I verify if the switch is defective? Technicians should check for continuity across the terminals when the switch is cool; a lack of continuity at room temperature indicates a failed "open" state requiring a replacement.

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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.