Pressure controls serve various functions, which may be divided into control and protection functions. Examples of control functions are compressor cycling, pumpdown, or defrost control. Protection functions included pressure limiting and cutout against excessive pressures, against loss of charge or for freeze protection.
Pressure controls (such as those manufactured by Alco, a division of Emerson Climate Technologies) are equipped with display scale and pointers to indicate the approximate settings. The display scale is printed in relative pressure units “bar” and “psi.” For precise setting of the controls, external gauges must be used.