Check the listing for details. Lennox 17M50 Humidity Sensor, 24 Volt, Wall Mounted. Condition: New. Listed at 80.00 USD. ***New in the box, never used*** The Lennox 17M50 Humidity Sensor is a wall-mounted duct sensor designed for HVAC and refrigeration systems. With a 24-volt power supply, this sensor accurately monitors humidity levels and transmits the data to the control system for efficient operation. The Lennox brand is known for its quality and reliability, making this model a trusted choice for businesses in the HVAC industry.