How to Install a Furnace Humidifier

By Gene and Katie Hamilton

Tools Required
  • Tin snips
  • Electric drill with bits
  • Pliers
  • Hammer
  • Nail punch
  • Small wrench
Materials Required
  • Furnace humidifier
  • Medium grade sandpaper
  • Masking tape

Before You Begin

End Closet Clutter

The humidifier uses a motor-driven evaporator pad that turns in the water pan. Warm air is by-passed from the warm air plenum and forced through the evaporator pad and returned to the cold air return duct. Identify the return duct usually leading to the base of the furnace, and choose the side that allows the best access for installation and maintenance. The humidifier must be installed so that if a leak occurs, the water could not cause any damage.

How to install a furnace humidifier is not an easy DIY job. Carefully read and follow the manufacturer's directions that come packaged with the unit. These general directions give you an overview of the installation process.

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  • Step 1 : Apply the humidifier template on the return duct

    Apply the humidifier template

    A typical installation is about 14-in. between the humidifier opening and the center of the air take-off collar. Place the template on the warm air duct to mark the location for screw holes to fasten the humidifier to the duct. Secure the template with masking tape. Then drill holes through the template and return duct's sheet metal. Screw sheet metal screws part way into the holes. Then use a tin snips to cut a rectangular opening for the humidifier that corresponds to the template. Below are directions about how to install a furnace humidifier.

  • Step 2 : Install the humidifier

    Hook the humidifier on the screws by passing the screw heads through the keyholes at the back of the humidifier; then let the humidifier sit in the slots. Check that the unit is level from side to side and back to back. Then tighten the screws to secure the humidifier to the duct. Install the motor unit inside the case according to the installation instructions.

  • Step 3 : Install the air take-off collar

     Install the air take-off collar

    Center the air take-off collar on the point marked on the warm air duct in Step 1. Hold the collar on the duct and mark fastening holes and the inside zone of the collar. Drill fastening holes and cut a round opening for the air take-off collar. Fasten the collar to the duct with screws.

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