How to Wire a Honeywell Whole House Humidifier


Whole house humidifiers replace the moisture that is lost from heating the air in your home. The Honeywell Whole House Humidifier uses a very simple system with a 24-volt transformer and a humidistat to allow the humidifier to turn on whenever the heat comes on. It also includes template stickers for all the holes that you must cut in the ductwork.

Things You'll Need

  • Screwdrivers
  • Cordless drill
  • Wire cutters
  • 18 gauge/ 2 conductor wire
  • Utility knife
  • Small wire nuts
  • Tin snips
  • Attach the humidistat hole template sticker included with the Honeywell humidifier to the return air duct. It should be located at least 12 inches above the humidifier or bypass duct. Cut out the dotted line with tin snips to make a hole large enough to accommodate the humidistat. Drill a small hole about one inch from the rectangular hole you have just cut and run an 18-gauge, two conductor wire through the drilled hole and out through the hole you have cut for the humidistat. Strip the insulation off of the two conductors of the 18-gauge wire and place under the two screws on the back of the humidistat. Tighten the screws to secure the wires. Secure the humidistat in place over the hole with screws.

  • Run the wire from the humidistat to the humidifier solenoid valve, the small cylinder with two wires sticking out from the bottom of the humidifier. Leave the wire intact and long enough to reach the blower compartment of the furnace or air handler. Strip the insulation from the outside of the 18-gauge wire with a utility knife, exposing the red and white sheathed conductors. Cut the white conductor with wire cutters and strip one-half of an inch of insulation from each end of the cut white wire. Leave the red conductor intact. Twist each end of the white conductor with each of the two wires from the solenoid valve, with the exposed copper ends touching. Twist a small wire nut onto each connection.

  • Cut the 18-gauge wire and route the wire to the blower compartment of your furnace or air-handler through the small hole in the side. Make sure it is long enough to reach the blower control panel inside the furnace. Strip off the insulation to the wire and the red and white conductors inside. Attach the 18-gauge wire to the control panel in order to power the humidifier in the heating cycle. To do this, insert the exposed copper ends of the wires under the terminal screws marked "W" and "C" and tighten the screws with a screwdriver. Some control boards have terminals for a humidifier. In that case, attach the two exposed copper wire ends to the terminals marked "Hum" and "C." Tighten the screws with a screwdriver.

  • Test the operation of your humidifier by turning up your thermostat. Run the dial on the humidistat all the way up. Make sure the water is on. Once the fan starts blowing, water should begin running through the humidifier and out the drain. Set the humidistat and thermostat to the desired settings.

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