How Does a Humidifier Work Inside Your Heater?

Humidity Level

• Wintertime humidity in your home should be maintained from 30 percent to 50 percent. Portable humidifiers can add moisture to a room, but whole-house units installed in your furnace humidify your whole home. Whole-house units are cost-competitive with portable humidifiers and, because they are connected to your household plumbing, refill automatically with water. They also use less electricity than portable units. There are three general types of whole-house humidifier: drum, wick and spray.

Drum Humidifiers

• Drum humidifiers are installed on the cool air return duct. In drum-type units, a foam or fabric belt is stretched over a drum-shaped frame that an electric motor rotates through a water tray to wet the belt. The drum faces an opening in the cold-air return duct. The hub of the drum empties into a large hose connected to the hot air supply duct. In operation, the motor turns the drum. Natural draft from the forced hot air supply duct sucks air from the return duct through the rotating belt where it picks up moisture. The natural draft pulls the moist air into the hot air duct, where it is distributed through the house.

Wick Humidifiers

• Wick humidifiers also install on the cool air return duct, with an outlet hose connected to the hot air supply duct. Instead of a rotating drum, these units use a loosely woven wick that’s kept saturated by a water spray from the top. Again, natural draft from the hot air supply duct sucks air through the wick where it picks up moisture. The moist air then is distributed through the house. These units don’t use electricity but do need a drain to carry away the water that doesn’t evaporate.

Spray Units

• A spray mist humidifier installs on the hot air supply duct. These units use an electronic mister to spray fine water droplets directly into the hot air stream when the heating system comes on. Fan-driven humidifiers are a variation on the wick type. They use an electric fan to suck air from the hot air supply duct, pull the air through a wick where it picks up moisture and push the moist air back into the hot air supply.