Lennox 88K90 Pressure Switch

The Lennox 88K90 Pressure Switch is a high-precision, OEM furnace safety component factory-calibrated for induction monitoring in residential and light commercial heating systems. This 0.47" WC pressure switch utilizes a single-pole single-throw (SPST), normally open contact configuration, ensuring the combustion process only initiates when proper draft is established. Designed for universal compatibility with older systems, the 88K90 replaces part number 88K9001 and is often found in 80MGF, 80UHG, and G24M series units. The 1/4" barb connection allows for a leak-proof interface with the vinyl tubing from the inducer housing. Built by Honeywell (Model IS20321-5518) for Lennox, this switch actuates precisely at 0.47 inches water column and resets around 0.62" WC. Professionals rely on this furnace pressure sensor to diagnose air proving issues and prevent hazardous short-cycling or combustion failures. Whether you are performing a seasonal tune-up or a critical repair, this air pressure switch provides the exact electrical rating and set point required to maintain system safety standards.

• Precise Actuation: Calibrated to .47" WC to ensure the draft inducer provides sufficient airflow before ignition.
• Seamless Compatibility: Direct OEM replacement for 88K9001, 88K90-01, and Honeywell IS20321-5518 models.
• Contractor-Grade Construction: Features a robust SPST normally open contact and an integrated mounting bracket for rapid installation.
• Reliable Connection: Standard 1/4" barb provides a secure fit for industry-standard vacuum hoses.

What is the trip point for the Lennox 88K90?
This switch is calibrated to close at .47" WC and typically resets at 0.62" WC to ensure the system operates within safe pressure limits.

Can I use this to replace part number 88K9001?
Yes, the 88K90 and 88K9001 are electrically and physically identical, serving as interchangeable parts in compatible Lennox furnaces.

Does this switch use a 1/4" or 1/8" hose connection?
The Lennox 88K90 is designed with a 1/4" barb connection, which is the standard size for most draft inducer tubing in modern furnaces.

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.