2202G1JE-DA-M-N_2010.01.
1 Safety
Reciprocating Compressor M Series
1.4 Safety Devices
1-11
1.4.5 Automatic Control and Protection Equipment M compressor
Overview/Function/Purpose
Low oil pressure failure protection equipment (OP)
When the oil pressure in compressor (Gauge pressure minus crank case pressure) drops from
deficiency of refrigerant oil, clogging of filter, and interfusion of refrigerant, automatically shuts off
the motor circuit and stops the operation of compressor.
This intended to prevent damage to the compressor from abnormal friction. Can also cause the
unloader mechanism from malfunctioning
High pressure protection equipment (HP)
When the discharge pressure on compressor becomes abnormally high because the compressor is
operated incorrectly or the water supply for condenser is cut. HP switch shuts off the motor circuit
automatically to stop the operation of compressor.
Prevents system ruptures and refrigerant leaks.
Control of the compressor capacity: Low pressure control equipment (LP)
The number of capacity control step in the compressor is determined by the number of cylinder.
Generally two cylinders are considered as one bank. Therefore, capacity control of four steps is
available for eight cylinders, three steps for six cylinders, and two steps for four cylinders. Capacity
control is performed by detecting suction pressure the low pressure control switch is used.
It automatically controls opening/closing of the solenoid valve connected to the unloader piston in the
capacity control mechanism of compressor.