Bypass humidifiers use the blower motor of the furnace while fan-powered humidifiers use their own fan to push air through the unit. The furnace must be running for a bypass humidifier to work; a fan- powered unit can operate on its own. Bypass humidifiers require extra ductwork, known as a bypass duct, and air must be recirculated back through the furnace before distribution into the home, whereas fan-powered units can be installed directly.
Because a bypass humidifier has no fan motor of its own, it only operates when the furnace runs. Fan-powered humidifiers have their own fan, and can operate continually, even when the heat is not on in your home. Fan humidifiers have the ability to humidify a home faster than a bypass humidifier.
With a bypass humidifier, humidity is added to the air and is recirculated to the furnace where the blower motor forces air into the home. Because air must be humidified then redistributed to the furnace before entering the home, a percentage of humidity is lost in the process. More water is used, but little coverts to humidity – most is used to flush the water panel to prevent mineral buildup from causing clogs.
Fan-powered humidifiers moisturize air and distribute it directly to the home, preventing humidity loss. These units are capable of producing around one gallon more humidity each day than a bypass humidifier. They have the power to add moisture across a larger square footage, making a fan humidifier an ideal choice for larger spaces. Water is more efficiently used compared to a bypass humidifier, with more water converting to humidity.
Since a bypass humidifier utilizes the furnace’s fan to move air, the furnace must be on for the humidifier to work. This can waste energy when only humidity is required, not additional heating. A fan-powered humidifier uses its own fan to move air, so it can operate without the furnace. This will save users money by preventing unnecessary heating. Because of the system’s fan, they do consume more electricity than a bypass humidifier, making a fan-powered humidifier more costly to operate.
A bypass humidifier operates at a quieter noise level than fan-powered humidifiers. This is because it does not have a fan running within the unit that adds to operating noise like a fan-powered humidifier.
Unit cost will depend on the selected model, though typically, fan-powered whole home humidifiers cost a bit more than bypass humidifiers.
Bypass humidifiers do require extra ducting for installation. These units are typically installed on the return air duct, and linked to the supply duct through a bypass duct. Due to the need for a bypass duct, installation of a bypass humidifier requires adequate space. They also have a bypass damper which must be manually opened for operation, and shut in the summer when added humidity is not needed in the home.
Because a fan-powered humidifier does not require bypass ducting, they can be installed in applications where space is limited. They are an ideal humidification solution for homes that have the HVAC system installed in a small utility closet or that are built on a slab.
Either type of humidifier can experience breakdowns when not properly maintained. Typically, bypass humidifier units experience fewer breakdowns and repair needs because the unit contains no fans, so there are fewer moving parts that could malfunction.
Both bypass and fan-powered humidifiers contain a water panel, which adds moisture to air passing through the unit. The humidifier’s water panel must be changed annually.