Lennox 19L57 Pressure Switch

The Lennox 19L57 Pressure Switch is a critical OEM safety component engineered for precise airflow monitoring in residential and commercial furnaces. This .25" WC pressure switch is designed to verify that the draft inducer motor is creating sufficient negative pressure to vent combustion gases safely before allowing the ignition sequence to proceed. As an SPST (Single Pole Single Throw) configuration, it provides a reliable normally open circuit that closes only when the specific 0.25-inch water column threshold is met, preventing unsafe operation due to flue blockages or inducer failure.

This genuine Lennox 19L5701 replacement features dual 1/4" barb connections for seamless integration with standard vacuum tubing. Built to exacting Lennox HVAC parts standards, it ensures consistent performance in high-demand environments. Whether you are troubleshooting an E271 soft lockout or a failing diaphragm causing intermittent ignition, this furnace pressure switch offers the exact specifications required to restore system integrity and maintain sequence-of-operation accuracy.

Key Benefits for Contractors:

• Exact OEM Match: Direct replacement for Lennox 19L57 and 19L5701, ensuring perfect mounting and electrical compatibility.
• Safety-First Operation: Calibrated to .25" WC to prevent furnace ignition under hazardous venting conditions or restricted heat exchangers.
• Durable Construction: High-quality internal diaphragm designed to withstand the thermal cycling and moisture typical of HVAC pressure switch applications.
• Simplified Installation: Standard dual 1/4" barb ports and screw terminals facilitate fast field replacement during service calls.

Common Questions:

What are the signs of a failing Lennox 19L57 pressure switch?
Common indicators include the inducer motor running continuously without the igniter glowing, short cycling, or specific LED fault codes (typically 9 flashes on many Lennox boards) indicating the switch failed to close during a call for heat.

Is the 19L57 compatible with all Lennox furnaces?
While used across many models, it is essential to verify the 0.25" WC rating on your existing part. Using a switch with the wrong set point can lead to safety risks or frequent system lockouts.

Can I use the 19L57 to replace a 19L5701?
Yes, the 19L57 and 19L5701 are identical components and can be used interchangeably in all supported Lennox equipment.

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.