List of Air Conditioning Control Device's

The control devices of Air Conditioning described below :-

Thermostats : 

 A thermostat is a device that operates by changes in room temperature. In some thermostats a bi-metal strip is used to make and break a set of contacts. In another design, the bi-metal strip is coiled into a loose helix, with outer coil rigidly fixed to the case. The inner coil is free to move in accordance with temperature changes, and to this free end is secured a glass capsule containing an ample charge of mercury. Two electric wires are seated in one end of the capsule, their base ends projecting into the capsule. When the capsule is tilted in one direction, the mercury flows to the lowest end ; if this happens to the plain end ; the circuit is broken. The electrical circuit is completed only when the capsule is tilted in the other direction, so that mercury flows to the end containing the two wire ends. The mercury bridges the space between the two wires and acts as a metallic conductor. 

Automatic Humidity Control :

Humidistat is an instrument which controls the humidity automatically. In the instrument the element is some type of hygroscopic material,such as wood, human hair, paper and similar materials, when the material absorbs water from the air, expansion takes place. It is this action that is used to make and break the circuit controlling hymidifying or dehumidifying apparatus.

Air Movement Control :

Movement of air is usually determine by factors viz., size of the blowers, the size of the ducts and supply grilles, and the speed of the blower motor. These factors are established when the system is installed and can only be varied by changing the motor speeds or by the manipulation of suitable dampers.

Automatic Temperature Control :

The automatic device that controls the temperature of the unit is the thermostat. It contains an element that is sensitive to changes in temperature. This element is usually a bi-metal strip or a metal bellows filled with a volatile liquid. An automatic temperature control system is generally operated by making and breaking an electric circuit or by opening and closing a compressed air line. Electrically operated systems are used by manufacturers for practically all installations whereas compressed air operated systems are employed in extremely large central and multiple installations.

Limit Switches :

The use of limit switches is made in heating installations to prevent the fan motor from circulating cold air when the heat is off. These are employed to prevent the humidifier from operating when the heat is off, or to cut-off refrigeration when heat is on.

Time Clocks :

Timers are merely clock-operated switches that can be placed either with the thermostat or manual switch, thus automatically praventing operation during certain periods.s

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