D7.8.3/0416/E 1/5
Date of last update: Apr-16
Application Engineering Europe
DWM COPELAND™ SEMI-HERMETIC COMPRESSORS
OIL PRESSURE DIFFERENTIAL SWITCH OPS2
1 Introduction
The OPS2 monitors the oil pressure differential protecting the
compressor against damage if the oil differential becomes too low.
Internal channels drilled through the housing link the switch to the
inlet and outlet ports of the oil pump.
The brass mechanical sensor component is fitted as standard on
all DWM Semi-Hermetic compressors which have a high pressure
oil pump. It is directly screwed into the pump housing. The black
electronic switch is screwed onto the brass mechanical sensor. If
the electronic switch has to be removed from the brass sensor the
refrigeration circuit will not be open to the atmosphere.
The mechanical sensor fitting for the OPS2 is the same as for the OPS1. The electronic switches are
interchangeable but require changes to the wiring circuit.
2 Function
The OPS2 is activated by the running signal of the compressor contactor. If the oil pressure differential drops below
the preset value for longer than the time delay (120 seconds) the output contact of the OPS2 opens and stops the
compressor providing protection against internal damage. Repeated shorter periods of insufficient oil pressure are
also recognized and will shut off the compressor after an appropriate time delay.
Figure 1: Functional graph using pressure differential x time axes
3 Operation
There is a 3-second delay after power is supplied to the OPS2 before the relay pulls in and the compressor is
ready to start. Once running the compressor contactor provides the signal to the OPS2 (D1). The differential
pressure monitoring will only start when the running recognition D1 signal is present. After a delay of 5 seconds the
OPS2 starts monitoring.
Electronic switch Mechanical sensor
Start of monitoring ∆p low for only a short time Compressor stop
Compressor start Compressor will not stop
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