Johnson Controls A19AAF-12 SPDT Remote Bulb Temperature Control 3.5 Fixed Differential 25°F-225°F 10' Capillary

The Johnson Controls A19AAF-12 is a remote bulb temperature controller that is used to control temperature of HVAC systems. It employs a thin tube called capillary which holds a liquid or a gas which changes in dimensions in relation to temperature changes. This capillary extends to a bulb at the detecting end which is placed in the required temperature control zone. Whenever the temperature is high or low, the expanding or contracting flexibility of the capillary affects an electrical switch consequently turning on the heat or cool equipment until the appropriate temperature is achieved.