Lennox R20402401 Liquid Line 3/8" Service Valve. Lennox goal is to provide contractors with high-quality HVAC solutions and replacement parts. This system includes changes and inventory updates to ensure peak performance. Lennox has a large line up parts and products for high-efficiency packaged rooftop units, split systems, HVAC controls, furnaces and indoor air quality products. The Lennox R20402401 Liquid Line 3/8" Service Valve is genuine replacement part designed for liquid freon.