The Aprilaire 1120 humidifier is a self-contained model, designed for installation in the conditioned space, and independent of the heating system. Hot water from a service water heater is supplied to the unit, and furnishes the heat necessary for evaporation. Air movement is accomplished by a two speed fan, which pulls dry air into the humidifier, through the Water Panel evaporator, and distributes humidified air into the conditioned space. Parts for the Aprilaire 1120 humidifier are listed below. This model is rated at 22# per hour.