Manual Digital Control Humidistat for Aprilaire 4655 The manual digital control humidistat is designed to be used with low voltage service to offer control of your humidification equipment, and is made to be used with the Aprilaire humidifier 4655 500. The manual humidistat is designed to be installed on the cold air return duct or on an interior wall in the living area of the home. To determine the relative humidity in the home, slowly turn the knob on the control clockwise and counterclockwise and listen for 2 clicks. The actual relative humidity in the home is between the 2 clicks.
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