A pneumatic thermostat is a specially designed device that controls the heating or air conditioning system of a house through a control tube filled with air that can send signals, and it works by using a metallic strip that can respond to temperature changes, says Do It Yourself. In response, it either decreases or increases the pressure in the control tube until it achieves a desirable temperature.
Power Electronics states that electronics found inside the pneumatic thermostat stay in a sleeping mode, waking up only every 15 minutes to check the temperature status and make necessary changes. This mode prolongs the battery of the thermostat to last as long as five years. Data is normally passed through a mesh network that utilizes several repeaters. For data to reach a central hub, it must pass through multiple redundant paths in a mesh network, says Power Electronics. Several components found within the unit respond to the pressure changes that occur inside the control tube. With the help of the duct work, pneumatic thermostats can activate cooling or heating as appropriate, says Do it Yourself. As temperature increases inside a room, the Direct Acting pneumatic thermostat, also called DA, increases the pressure in the branch lines. The Reverse Acting pneumatic thermostat, on the other hand, decreases the pressure when temperature increases.