Lennox 11U71 Pressure Switch

The Lennox 11U71 High Altitude Pressure Switch is a critical safety component designed for furnace pressure switch replacement in systems operating at elevations between 4,500 and 7,500 feet. Calibrated with a precise 0.85" WC (water column) actuation point, this OEM Lennox part ensures the inducer motor generates sufficient static pressure for safe combustion before allowing the gas valve to energize. This specific 104371-08 model is a SPST-N.O. (Single Pole Single Throw, Normally Open) switch, rated for 24VAC systems at 5 Amps resistive.

For technicians performing field service, the 11U71 is an exact functional equivalent to the NS2-1399-08 pressure switch. Accurate pressure detection is vital in thinner mountain air to prevent furnace short cycling or delayed ignition. Proper installation requires verifying the .85-inch vacuum rating matches the existing system specifications to maintain strict HVAC high-altitude compliance. This switch replaces several legacy part numbers, including 103614-18 and 93W9301, providing a reliable solution for restoring heating performance in low-pressure atmospheric conditions.

• Precise Calibration: Factory-set to 0.85" WC for high-altitude accuracy, preventing safety lockouts related to thin air density.
• Direct OEM Compatibility: Engineered as a drop-in replacement for Lennox furnaces, cross-referencing directly with NS2-1399-08 and 104371-08.
• Enhanced System Safety: Monitors inducer motor airflow to ensure flue gases are properly vented before the burner cycles.
• Robust Electrical Rating: Features 24V SPST contacts capable of handling 5 Amp resistive loads common in residential HVAC controls.

• Why is a high-altitude switch necessary? Higher elevations have lower atmospheric pressure; a standard sea-level switch may fail to close even when the inducer is running correctly. This high-altitude pressure switch compensates for that difference.
• Can I use this switch at sea level? No. Using a .85" WC switch calibrated for altitude in a sea-level application can lead to unsafe operation or damage to the heat exchanger.
• What does it mean if the switch stays open? This usually indicates a clogged vent pipe, a failing inducer motor, or moisture buildup in the vacuum tubing.

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.