Controls and other circuit components

A refrigeration system can be built with only the four essential components  

Eor ease, economy, and safety of operation, and to assist the maintenance function, other system controls and components will be fitted. 

Since the purpose of a refrigeration or air-conditioning system will be to reduce or maintain temperature, a thermostat will usually be fitted to stop the equipment or reduce its capacity when the required condition is reached. The following types are in use  

The above produce a mechanical effect which can be used direcdy to operate an electric switch or modulate the pressure of an air jet (pneumatic system). 

These last two produce an electric signal which must be measured and amplified to operate the controlled device. 

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