How to Add Whole House Air Filtering Onto a Furnace

Most furnaces have some type of built-in filtering system. While this type of system keeps dust to a minimum and protects the furnace blower and motor, an add-on filter system may be just the ticket if you need extra filtering. A filtering cabinet can be added to your existing furnace to provide an extra layer of protection by trapping smaller particles than a standard furnace filter. This type of filter may be beneficial to those in your household with allergies.

Filtering cabinet with filter cartridge
Nut driver set
Wood shims (Optional)
Sheet metal screws
Handheld drill
1/8-inch drill bit
Duct tape

Instructions

- 1
  Remove the filter cartridge from the filtering cabinet. Position the filtering cabinet on the floor near the return air opening on your furnace. Ensure the cabinet position will allow for easy installation and removal of the filter cartridge once it is installed.
- 2
  Detach the sheet metal screws that attach the furnace duct work to the furnace's return air opening with a nut driver. Pull the duct work far enough away from the furnace to allow the installation of the filtering cabinet.
- 3
  Slide the filtering cabinet into the gap between the furnace and the duct work. Shim the underside of the cabinet with blocks of wood to help line up the cabinet with the return air opening on the furnace, if necessary.
- 4
  Secure the cabinet to the furnace at the return air opening with sheet metal screws. Drill new screw holes with a 1/8-inch-diameter drill bit if the original duct work mounting holes in the furnace do not line up with the mounting holes in the cabinet.
- 5
  Line up the furnace duct work with the opening on the filtering cabinet. Secure the duct work to the cabinet with sheet metal screws driven in with the nut driver.
- 6
  Seal the joints between the filtering cabinet and the furnace and duct work with duct tape. Cover all screws and screw holes to ensure there is no air leakage when the furnace is running.
- 7
  Line up the filter cartridge so that the arrow faces the direction of airflow into the furnace. Push the cartridge into the filtering cabinet until it is fully seated. Close or attach the door to the cabinet if one is provided.

How to Replace Plastic With Metal Ductwork

How to Move an A/C Vent to the Ceiling

Heating & Cooling Repair