The GeneralAire 4745 is the correct replacement air switch for the following air cleaner models:
The GeneralAire D1-0217 Air Cleaner Air Switch is a replacement air switch for the GeneralAire GA50A14, GA50A20, and GA50A22 Electronic Air Cleaners. The D1-0217 air proving switch is installed in the power box of your humidifier next to the indicator light. The GeneralAire 4745 electronic air proving switch cycles your air cleaner on and off with the system fan.
GeneralAire D1-0217 Air Cleaner Air Switch specifications: