The GeneralAire 12500 is the correct replacement for the following humidifier:
The GeneralAire 12500 Humidifier Air Pressure Switch is also known as part number 7021 for the 1099 Bypass Humidifier. This air pressure proving switch prevents operation of the humidifier if there is no air flow in the duct, and helps to prevent moisture build-up in the duct system. On furnaces with a 2-speed blower motor or when wiring within your furnace is not practical, the GeneralAire 1099 Humidifier and the air pressure switch may be wired from a continuous 115-volt power source.
General Aire 12500 Air Pressure Switch Replacement specifications:
The on/off switch along with the GeneralAire Air Pressure Switch can be installed in series with the 115 volt solenoid valve on the hot or black wire. The GeneralAire 12500 Air Pressure Proving Switch will detect the operation of the furnace and supply power to the humidifier. GeneralAire is also known by the following spelling variations: General Aire, General Air and GeneralAir.