The Model 5558 Automatic Digital Modulating Control package is the recommended humidistat for the Aprilaire modulating steam fan pack ductless humidifier, Model 866.
The Aprilaire Automatic Digital Modulating Control (ADMC) is designed to be mounted on a wall in the living space. The ADMC provides precise humidity control by providing a variable output to the humidifier based on the difference between the set point on the control and the sensed humidity. The proportional band default is 5% RH and can be varied from 2% - 10% in increments of 0.5%.
The Outdoor Sensor is used for temperature compensation to prevent window condensation.