Close humidifier damper in summer

Air Conditioning and Heat Pumps · Thermostats · printed page 224 (PDF page 225)

Book index entries

Air Conditioning – Close Humidifier Damper Humidifier – Dampers Closed – Air Conditioning Duct System Ducts – System for Air Conditioning

Text in the illustration

supply plenum
return air
humidifier duct damper
close off air flow in summer
open in winter
air flow
evaporator coil
Humidifier
if the humidifier damper isn't closed, cool air can be drawn back into the cold air return and over the evaporator coil in a short circuit loop
this can lead to icing up of the evaporator coil

Generated explanation

The illustration shows a drum-type bypass humidifier connected between the supply plenum and return-air duct, with an evaporator coil indicated below the supply plenum. Arrows trace airflow through the humidifier bypass and back through the return duct, creating a short-circuit loop when the humidifier damper remains open. The annotations warn that this recirculation of cool air can cause evaporator coil icing. The recommended seasonal practice is to close the humidifier duct damper in summer and open it in winter.

Related illustrations

0787

Air flow through humidifier

· p. 130

The illustration shows a drum-style bypass humidifier mounted on the cold-air return of a forced-air heating system. A flexible bypass duct connects the supply plenum to the humidifier, with arrows showing airflow from t