How to Hook a Dehumidifier to Your Furnace

Attaching a whole-house dehumidifier to a furnace allows it to work on the entire building, unlike a single-room unit.
Air is filtered through the dehumidifier and its humidity level reduced before the furnace distributes the air throughout the building. The lower humidity inside deters mold growth, mildew growth, allergies and stains from moisture. Most building residents opt for a whole-house dehumidifier for comfort and energy conservation, since a less humid environment provides more comfort without using energy to lower the indoor temperature.

Step 1

Place the dehumidifier in the proper location near the furnace. It must sit as close as possible to the furnace's return air duct, with plenty of room for access to the filter access panel on the front of the dehumidifier and the electrical access panel. The ambient temperature around the dehumidifier should remain within 40 and 125 degrees Fahrenheit, with an accessible grounded electrical source nearby.

Step 2

Disconnect the dehumidifier from the power source if applicable.

Step 3

Attach 3/4-inch PVC pipe to the condensate drain outlet on the furnace. The instruction manual for the dehumidifier should outline the location of the condensate drain outlet if it is unclear.

Step 4

Run the PVC pipe so that it reaches an outdoor drain.

Step 5

Connect the discharge air supply on the dehumidifier to the return air supply on the furnace using the 10-inch duct.

Step 6

Attach the return air supply on the dehumidifier to the return air supply on the furnace using the other length of 10-inch duct. This should be located near the furnace's return air grill. There are two connections from the dehumidifier to the return air supply on the furnace. The first one (Step 5) acts as an intake for the dehumidifier. The second, expels the air back into the furnace's return air supply after it has been dehumidified. This air is what gets pushed through your vents.

Step 7

Close up the connections with sealant to ensure they remain efficient and don't lose air through the connections.

Things You Will Need

  • 3/4-inch PVC pipe
  • Two 10-inch insulated, flexible ducts
  • Sealant

About the Author

Bryan Clark has been a freelance writer since 2002. His work has appeared in "The New York Times," "USA Today" and the U.K.'s biggest paper—"The Guardian," amongst other, smaller publications.