How do I Install an Aprilaire 445 Humidifier?

Unpack the Aprilaire Humidifier Control carton. Verify if the package contains the following components: humidifier control, outdoor temperature sensor, manual mode label and manual mode resistor case. Pull the bottom of the humidifier control door straight out to easily dislodge and remove it.

Adjust the setting on the "Bypass" and "Power" switches to the humidifier model type. For instance, the Aprilaire 445 humidifier belongs under the "Power" classification. Check the "Change Water Panel" setting, which has an indicator light that reminds the operator to change the water panel.

Find a location to mount the humidifier control in the return duct. Mount the humidifier control within 6 inches upstream of the humidifier, humidifier bypass duct-work and fresh air intake. Use the humidifier control template to trace the duct orifice, then use duct cutters to create it. Position and thread four sheet metal screws through the guideposts on the humidifier control in the duct opening. Tighten all four metal screws with a Phillips screwdriver until completely flush against the duct work.

Find a location for the outdoor temperature sensor that faces either the north, east or west side of the house out of direct sunlight, sits within 3 feet of all exhaust vents, and lies above the expected snow line. Choose a 2-inch PVC fresh air intake furnace pipe or 6-inch fresh air intake duct as an alternative location to mount the outdoor temperature sensor. Mount the sensor with a number 8 galvanized screw.

Select a location for an existing access hole that leads outdoors, such as one for an air-conditioning condenser unit, television set, or a telephone's wire outlets. Read the equipment's operation instructions to avoid unnecessary damages or conflicts.

Run the wire to the outdoor temperature sensor, making sure to avoid high-voltage wires with 120 VAC or higher. Mount the sensor bracket to the house with a number 8 galvanized screw.

Strip 1/4-inch wire insulation and insert the wires from the outdoor temperature sensor to the "ODT" terminals on the humidifier control.

Choose an appropriate power source for the humidifier control with furnaces that have accessory terminals. Run the 24 VAC wires directly to the "R" and "C" terminals on the humidifier control, or route any existing 120 VAC wires directly to a 24 VAC transformer. Connect the wires to the "R" and "C" terminals. Verify whether the voltage leading to the humidifier control reads between 22 and 30 VAC.

Strip 1/4-inch insulation from the humidifier control terminal connector wires. Wire the solenoid valve directly on to the "H" terminals located on the humidifier control.

Connect a Model 50 current sensing relay to the solenoid valve and the "H" terminals only when using an external transformer. Connect the Model 50 relay to the "H" circuit only. Repeat the same process when wiring the "Bypass" and "Power" units to the AHC.

Conduct a system's checkout to finish the installation by verifying the "R" and "C" terminal connections. Replace the humidifier door. Turn on the furnace blower and check the thermostat for the appropriate heat range. Rotate the humidifier control knob clockwise into the "Test/Reset" position and check for the green "Change Water Panel" light to blink. Readjust the "Test/Reset" knob back into its home position. Set the humidifier control to "Normal," or 35 percent for manual operation. Refer to the troubleshooting guide if any malfunctions arise in the humidifier control. Set it to "Off" when leaving your house. Refer to the troubleshooting guide if the red diagnostic light is activated.