How the Aprilaire® Steam Humidifier Works

The Aprilaire® Steam Humidifier efficiently delivers humidity in the form of steam through either the HVAC duct system or a Fan Pack. It generates steam by passing an electric current between two electrodes submerged in a canister of water, causing the water to boil.

Water Flow and Regulation

• Water enters the humidifier through a fill valve into a fill cup, which serves as an overflow reservoir and creates an air gap between the humidifier and the water source.

• The steam canister fills from the bottom and sits in a drain cup assembly that includes a drain valve.

• The fill and drain valves work together to maintain the proper water level, ensuring optimal steam output based on the water's electrical conductivity and tempering drain water before disposal.

Steam Distribution & Control

HVAC System Integration (Model 62 ADHC)

• The Model 62 Automatic Digital Humidifier Control (ADHC) detects relative humidity (RH) in the duct system.

• When RH drops below the set point and the HVAC blower is running, the humidifier activates, sending steam through a hose and dispersion tube into the ductwork.

• The Tubelets™ in the dispersion tube distribute steam evenly while directing condensed moisture back into the hose.

• The ADHC's blower activation feature allows the blower to run independently to maintain humidity, even when the furnace or air handler is in standby mode.

Standalone Operation with Fan Pack (Model 65 Manual Humidistat)

• The Model 65 Manual Digital Humidistat detects low RH and activates the humidifier.

• Steam is released through the steam manifold at the bottom of the Fan Pack.

• A built-in fan disperses steam into the living space and continues running for two minutes after the humidity call ends to clear residual steam.

Modulating Control for Precision (Automatic Digital Modulating Control - ADMC)

• The Automatic Digital Modulating Control (ADMC) is installed in the living space for precise humidity management.

• It adjusts steam output based on the difference between the set RH and actual RH, sending a proportional signal to the humidifier.

• The ADMC can also be used for On/Off control with non-modulating steam humidifiers, replacing both the ADHC and Model 65 Humidistat for a streamlined control setup.

For installation and operation details, refer to the ADHC, ADMC, or Fan Pack manuals.