Lennox 27K79 Limit

The Lennox 27K79 175F Limit is a critical safety component designed for precise thermal regulation within the furnace plenum. As a primary high-limit control, this genuine OEM replacement part is engineered to interrupt the electrical circuit to the gas valve if internal temperatures exceed the 175°F threshold, effectively preventing heat exchanger damage and ensuring system safety. This furnace high limit switch features an automatic reset mechanism that restores circuit continuity once the temperature drops to the 145°F cut-in point. Field technicians should note that the Lennox 27K79 is physically and functionally identical to part number 27K7901, offering a 3-inch insertion length for standard mounting applications. It is commonly utilized across a broad range of Lennox and Allied-branded equipment, including LF24 unit heaters and various furnace series. When troubleshooting Lennox error code 201, verifying the integrity of this 175-degree limit switch is a standard procedure. This automatic reset limit ensures consistent HVAC furnace safety by monitoring airflow-related temperature spikes that can lead to catastrophic component failure.

• Precise Thermal Protection: Strictly calibrated to open at 175°F and close at 145°F for safe furnace operation.
• OEM Compatibility: A direct Lennox 27K7901 replacement, ensuring exact fitment and electrical specifications are met without field modifications.
• Automatic Reset: Eliminates the need for manual intervention after a temporary overheat condition, once the system returns to a safe operating temperature.
• Robust Construction: Designed with high-grade materials to withstand the high-cycle demands of residential and commercial HVAC systems.

• Is the 27K79 a universal part? While it fits many Lennox, Armstrong, and Ducane models, it is application-specific based on the 175°F setpoint and 3-inch probe length.
• What causes this limit to trip repeatedly? Frequent tripping is usually indicative of restricted airflow, often caused by a clogged filter, closed registers, or a failing blower motor.
• How do I confirm if my 27K79 is faulty? A technician should check for continuity across the terminals when the furnace is cool; a normally closed circuit is required for ignition.

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.