What is the Difference Between Bypass and Fan-Powered Humidifiers?

The most popular types of humidifiers are Bypass and Fan-Powered Humidifiers.  These are both duct-mounted, whole-house humidifiers that can efficiently humidify an entire home depending on the capacity of the unit.

1

Bypass units use a “bypass duct” to get the warm air from the furnace to the humidifier without having the humidifier located on the supply side. The warm air leaving the furnace takes the path of least resistance, flows into the bypass duct, and into the humidifier creating humidity. (Aprilaire 400, Aprilaire 500, Aprilaire 600)

 

2Fan-powered humidifiers are easier to install because they require no additional ductwork.  The unit use a fan to push air through and does not need to pull air from the furnace.  This aspect makes it faster and more efficient at humidifying the home while using a minimal amount of electricity.  Fan powered humidifiers typically can humidify more square feet than bypass humidifiers.  (Aprilaire 700)