Lennox 49L91 Pressure Switch

The Lennox 49L91 is a critical safety component designed for precise furnace draft monitoring within high-efficiency heating systems. This OEM Lennox Pressure Switch (also identified as 49L9101) is factory-calibrated to actuate at .51" WC and reset at 0.61" WC, ensuring the inducer motor maintains the necessary vacuum for safe combustion and flue gas venting. Featuring a SPST (Single Pole Single Throw) configuration and a standard 1/4" barb connection, it provides a reliable interface for sensing atmospheric differentials.

As a veteran-grade HVAC induction air switch, this part is compatible with a wide range of Lennox, Armstrong, and Ducane equipment, including the G40UH and G50UH series. The 5 Amp resistive contact rating at 24 VAC ensures heavy-duty electrical performance. When troubleshooting a pressure switch stuck open error code, verify your tubing integrity and inducer RPM before replacing. This unit is an essential heating system replacement part for technicians requiring exact OEM specifications to restore furnace sequence of operation.

• Direct OEM Replacement: Fully interchangeable with part number 49L9101 and Honeywell IS20100-3073 for seamless field installation.
• Precise Set Points: Factory-set .51" WC actuation provides accurate combustion air verification.
• Contractor Grade Durability: Engineered to withstand the high-cycle demands of residential and light commercial gas furnaces.
• Universal Barb Size: Standard 1/4" port allows for secure pneumatic hose seating without specialized adapters.

Is the Lennox 49L91 compatible with other brands?
Yes, this switch is the official replacement for several Lennox, Armstrong, and Ducane models. Always verify the WC (Water Column) rating on the original switch body before installation.

What does it mean if my furnace throws a "pressure switch open" code?
This typically indicates the switch is not detecting the required .51" WC vacuum. Check for blocked venting, a failing inducer motor, or cracked pneumatic tubing before concluding the switch is faulty.

Can I use a switch with a different WC rating?
No. Using a switch with a different set point can lead to unsafe combustion or nuisance tripping. Stick to the Lennox 49L91 .51" WC specification for this circuit.

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.