Description
The Johnson Controls W42AA-1C 3-Wire SPDT Humidistat Control is an electrical humidity control component designed to regulate moisture levels in HVAC systems. Operating on 120–240V power, it monitors ambient humidity and activates connected equipment when preset conditions are reached. It is commonly installed in ventilation units, humidifiers, and dehumidification systems used in residential, commercial, and light industrial environments. Within the system, the humidistat operates as a control component that signals fans, humidifiers, or dehumidifiers to operate, helping maintain balanced indoor humidity and supporting stable conditions.









