Includes Modulating Humidistat, Duct Sensor, Blower Activation
Relay and Outdoor Temperature Sensor
The Model 63 Automatic Digital Modulating Control (ADMC)
package is the recommended humidistat for the Aprilaire
modulating steam humidifier, Model 801.
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 Duct Sensor can be installed in the return duct and used as the controlling sensor or it can be used as a high limit
sensor. When used as the controlling sensor the RH level in the return duct is communicated to wall mounted control.
The wall mounted control will compare the RH from the duct sensor and set point from the control to modulate the output
signal. When used as a high humidity sensor the Duct Sensor is installed in the duct 4’– 5’ downstream of the steam
dispersion tube. If high humidity is detected in the duct the control will send a signal to the humidifier to decrease the
steam output. (The duct sensor is not used with the Model 866 Steam Humidifier with Fan Pack.)
The Blower Activation Relay is used to turn on the HVAC systems blower when there is a call for humidity and the HVAC
systems blower is off. The humidification system must have control of the HVAC systems blower to achieve proper
humidity levels and allow the humidifier to modulate properly. (The duct sensor is not used with the Model 866 Steam
Humidifier with Fan Pack.)
The Outdoor Sensor is used for temperature compensation to prevent window condensation.