The Aprilaire Water Panel Evaporator model number 45 is the original manufacturer's replacement humidifier pad (also called humidifier filter) for the Aprilaire models 400 and 400A whole house Humidifiers.
The size of the 45 replacement humidifier filter is approximately 10" x 12 3/4" x 1 3/4". The Water Panel Evaporator is the heart of your humidifier and the component which generates the important humidity needed to keep your home comfortable during the heating season. The water panel slides into the scale control insert and the water distribution tray sits on top of it to evenly distribute water to the water panel.
The Water Panel Evaporator must be in good condition to assure the high capacity trouble-free performance of your humidifier. The manufacturer recommends changing your humidifier pad annually under normal operating conditions. If you have especially hard water you may need to replace your humidifier filter 2 times per year.
For instructions on how to change your humidifiers water panel please refer to the "Maintenance Instructions" section of your units owner's manual.
This package ships with 2 filter pads.