The Aprilaire 4258 is the correct replacement for the following humidifiers:
The Aprilaire 4258 Humidifier Control Relay is used to turn on the fan motor or pump motor of your Aprilaire whole house humidifier. This humidifier relay kit works with your select commercial and residential model of humidifier.
The Aprilaire 4258 Specifications:
The Aprilaire 4258 humidifier control relay is located inside your fan power and recirculating type humidifier. The relay is easy to install and is an essential component of your whole house humidifier.