As a compressor starts, a heavy load is imposed on the drive motor. The crankcase pressure will be at its highest against normal or abnormal loading.
The function of the regulator is to keep the pressure in the crankcase to a reasonable level to protect the motor from overload. This applies when the evaporator pressure is above normal operating pressure, for example:
1. During the initial start-up after defrosting.
2. During periods of high starting loads.
3. Under high suction pressure caused by hot gas defrosting.
4. During surges in suction pressure.
5. Under prolonged high suction pressure.
The regulator is installed in the suction line as shown in Figure 83.
As a guide, the control should be set to the following crankcase pressures:
Hermetic and semi-hermetic compressors: 2.5 bar
Open-type compressors with standard motor: 3.0 bar
Open-type compressors with oversized motor: 4.5 bar.
Final adjustments are made to make the running current