Humidifiers are installed in CRAC systems to increase the amount of moisture in the air. A humidifier is an optional component in computer room air conditioning. CRAC systems may or may not have this component. Recall that high humidity in a computer room can corrode the equipment and can cause short circuits.
The humidity control logic is similar for most manufacturers of CRAC units. On a call for dehumidification, the cooling mode is activated. As the room temperature decreases the unit will active the reheat. This reheat will temper the air leaving the cooling coil, allow the air to absorb more moisture.
The humidifier is turned on whenever the humidity level for the system drops below the target Min Inside Humidity set in the systems page. The humidifier will be turned off after being turned on when humidity goes humidity Hysteresis above the target Min Inside Humidity.
With higher relative humidity, water evaporates more slowly from your skin, and the air feels slightly warmer. Due to this effect, using a humidifier may help reduce your heating usage during the colder seasons.