Lennox 27W17 Pressure Switch

The Lennox 27W17 Pressure Switch is the OEM replacement required for precise inducer fan monitoring in several gas furnace models. This SPST-NO (Normally Open) snap-action switch is factory-calibrated to actuate at -0.85" W.C., ensuring the combustion air blower is generating sufficient draft before the ignition sequence begins. Designed to replace obsolete part numbers 56M06 and 56M0601, this component features a 101256-01 manufacturer number and handles a 5 Amp resistive load at 24 VAC. Modern HVAC systems rely on this differential furnace pressure switch to prevent hazardous operation during venting blockages or motor failure. Its high-reliability design by MPL is compatible with Lennox, Armstrong, and Ducane equipment. Contractors should verify the water column rating on the existing failed switch to ensure a 27W17 Lennox cross-reference matches the specific pressure requirements of the heat exchanger.

Key Benefits

• Direct OEM Compatibility: Serves as the exact factory replacement for 56M06, 56M0601, and 101256-01, ensuring a drop-in fit without bracket modifications.
• Precise Safety Calibration: Fixed at -0.85" W.C. to maintain strict adherence to combustion safety standards and prevent furnace short-cycling.
• Industrial Build Quality: Rated for 125VAC and 5A resistive applications, providing durable performance in high-cycle residential and commercial environments.
• Broad Model Support: Optimized for popular Lennox G51MP, G61MP, and G43UF series gas furnaces.

Common Questions

How do I know if the Lennox 27W17 is the correct replacement for my furnace?
Confirm that your existing switch is stamped with 101256-01 or has a set point of 0.85" W.C. This switch is specifically designed for systems requiring a normally open configuration that closes upon sensing negative pressure from the inducer.

What are the symptoms of a failing Lennox pressure switch?
Common indicators include the furnace inducer running without the ignitor sparking, or diagnostic LED codes indicating a "pressure switch stuck open" or "pressure switch stuck closed" error. Always check for blocked vent pipes or a failing inducer motor before replacing the switch.

Can I use a universal pressure switch instead of the 27W17?
While universal switches exist, OEM Lennox parts are recommended to ensure the exact 0.85" W.C. trip point is maintained. Using a switch with an incorrect pressure rating can lead to incomplete combustion or safety circuit failures.

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.