The Aprilaire 4148 is the correct replacement for the following humidifiers:
Aprilaire humidifiers keep the relative humidity in your house at the proper level, providing maximum comfort. The humidifier works with the furnace blower motor. Water is sent to the distribution tray at the unit's top when the humidistat indicates that humidity is needed and the furnace blower is operating. The water is evenly spread across the tray and then flow via gravity over the Water Panel evaporator. The dry, hot air from the furnace blows through moisture soaked Water Panel evaporator, causing evaporation to occur. Humidified air which contains moisture in vapor form then flows throughout the house.
Aprilaire Humidifier Impellor Specifications:
The Aprilaire 4148 Humidifier Impellor is the small propeller that sits in the reservoir, driving water up the feed tube to the unit's water distribution tray, where humidity is created when the water flows over the Water Panel evaporator.