The Aprilaire 4655 is the correct replacement for the following humidifiers:
The Aprilaire 4655 Manual Humidifier Humidistat is a manual humidistat that has to be adjusted based on the outside temperature. This will help prevent water from running down the windows. Also known as part number 4655, this whole house humidistat is designed for low voltage (24v) control of humidifiers in central heating and air conditioning systems to control humidification equipment. Cool air near the windows cannot hold the humidity and water will condense on the glass. In order to prevent this accumulation of condensation, the indoor humidity level is sacrificed by lowering the humidistat.
Aprilaire Humidifier Humidistat specifications:
The Aprilaire humidistat control can be mounted on the wall or on the return plenum. A template for the plenum cutout is included. When installing this humidistat for duct mount, locate at least 6 upstream of your humidifier, humidifier bypass ductwork or fresh air intake ductwork. When an increase in relative humidity (RH) expands the nylon ribbon will open the control switch to stop the humidifier's operation. When a decrease in relative humidity reverses the process, the control switch closes.