Johnson Controls T-4000-2145 Beige Plastic Cover Vertical With 1 Window

The Johnson Controls T-4000-2145 is a beige plastic cover that is made to fit only vertical mounted pneumatic thermostats. It is not a thermostat as such, but an extra which adds protection and aesthetics to the thermostat. These are thermostats whose working is based on regulation of temperature by compressed air. A sensor within the unit senses changes in temperature within the room. When the temperature increases, then the pressure in the system also increases. It goes further to alter the HVAC, for example the change of position of a damper to allow fresh and cool air into the room.