Emerson DWM COPELAND OPS2 Manual

D7.8.3/0416/E 1/5

Not to scale

0.95∆p

Date of last update: Apr-16

Ref: D7.8.3/0416/E

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

OPS2

Start of monitoring ∆p low for only a short time Compressor stop

Compressor start Compressor will not stop

D7.8.3/0416/E 2/5

In case of failure or incorrect assembly registered for more than 5 seconds, the relay will trip and lock out.

Methods to reset the switch after shutdown:

Push the internal reset button (1 sec)

Disconnect the switch from the power supply –mains interruption (5 sec)

Remote alarm reset function (1 sec)

After a time delay of 120 seconds the compressor is able to operate again.

4 Technical information

4.1 Technical data

Power supply

115 –230V AC, –15%...+10%, 3 VA 50/60 Hz

Ambient temperature range

–30°C +70°C

Restart relay after tripping

120 sec ± 5 sec

Start-up delay

3 sec ± 1 sec

Differential pressure

0.95 ± 0.15 bar

Connection cables

6 x AWG18 (0.75 mm2), L = 1m colour coded

Maximum pressure

30 bar

Refrigerant compatibility

Yes (brass)

Protection class according to EN 60529

IP54

Reset

Manual

Weight

210 g

LED status: 2 x flashes at start up

Software version

LED status: 1 x flash after 2 x flashes above

Standby version

LED status: Continuous red light

No differential pressure

LED status: 10 Hz flashing –10 times per sec

Malfunction:

- Internal malfunction

- Internal power supply is too low

- Sensor not correctly mounted into mechanical part

- Running signal ON, but relay OUT

LED status: 1 Hz flashing –1 time per sec

Restart delay

LED status: LED off

Correct operation

4.2 Dimensions

Figure 2: Dimensions of the OPS2

4.3 Wiring diagram OPS2

Where there is a 5-wire cable connection between the electrical control panel and the compressor terminal box to

the OPS module, the same wires can be applied to the OPS2 which will give the functions of an OPS1 module.

To obtain use of all of the features of the OPS2 a 7-wire cable between the electrical control cabinet and the

compressor terminal box should be used. Wiring diagrams for both the OPS1 and OPS2 are shown on page 5. The

wiring diagram in Figure 3 relates to an option using a 7-wire cable.

LED Internal reset

(red) button

D7.8.3/0416/E 3/5

NOTE: Where a 5- or 7-wire cable is stated a 4- or 6-wire cable is required. In some countries only a 5- or 7-

wire cable is available.

Wiring:

Brown (BN) = Power supply input

Violet (VIO) = Running signal from compressor

Grey (GR) = Input changeover contact from daisy chain

Orange (OG) = Output changeover contact linked to

compressor contactor

Pink (PK) = Output changeover contact linked to alarm

Blue (BU) = Power supply output

Figure 3: Wiring diagram for OPS2 with a 7-wire cable

5 Installation advice

The brass mechanical sensor component is standard on all DWM and Copeland semi-hermetic compressors with

an oil pump, except on Stream -D. If it has to be fitted follow the procedure below:

Wear proper safety clothing and follow the correct Codes of Practice.

Isolate the compressor mechanically and electrically.

Evacuate the compressor.

Remove the plastic cover from the OPS sensor connection.

Screw the OPS2 electronic switch on to the mechanical sensor and tighten it by hand to 10 Nm. At the same

time ensure the electrical leads are running downwards.

Make the electrical connections for the OPS2 as per the wiring diagram in Figure 3.

Evacuate the compressor to extract any air contamination.

Set the compressor up for normal operation confirming the tightness of the electronic switch.

6 Commissioning

Switch the compressor on and wait until stable operating conditions are obtained.

If insufficient oil differential pressure is built up during start-up or during operation after the time delay expires, the

output contact will switch off and mechanically lock out. The power supply to the contactor coil will be interrupted

and the compressor will be switched off. Restart is possible after reset and after a time delay of 120 seconds.

D7.8.3/0416/E 4/5

7 Function testing

The OPS2 has to be set up as normal with fuses removed from power supply to compressor. The control circuit

should still be live.

7.1 Correct assembly control test

7.2 Brass mechanical sensor - Test differential pressure too low

Control power supply ON

Cooling required - Thermostat closed circuit

Differential pressure too low –120-sec time delay

LED code = continuous red light

After time delay, compressor contactor changes to alarm

(GR-OG to GR-PK) - Fault signal

Reset mains (5 sec)

Restart time delay 120 sec - LED code 1Hz

7.3 Running signal - Electronic switch not connected to the brass mechanical sensor

Control power supply ON

LED code = fast light 10Hz

Shut-off and locked out after 5 sec

Fit the electronic switch to the mechanical sensor

Push remote reset

Restart time delay 120 sec - LED code 1Hz

8 OPS1 and OPS2 comparison

FUNCTION

OPS1

OPS2

Connecting cable AWG 18

√

UL / CE conformity

√

Status LED with fault blink code

√

Screw in part compatible (P/N 3110784)

√

Reset function

√

Anti-tie down

√

Potential free change over relay –Dry contact

√

Dual voltage (115…230V)

√

Correct assembly (mechanical & electronic)

√

Remote alarm reset function

√

Advantages:

Easily mounted –screwed directly into the pump housing –time reduction.

Hermetically sealed –no external capillaries required –no leakage possibility.

Anti-tie down –the reset button cannot be forcibly held pressed in position bypassing the function of the

switch.

Retrofit possible –the electrical switch can be replaced without refrigerant loss.

Potential free change over relay –control with contactor and alarm possible.

Microprocessor technology –the latest technology.

If the electronic switch and the mechanical sensor are assembled incorrectly the compressor will shut off and be

locked out after 5 seconds.

Control power supply ON

Alarm contact switches to compressor contactor

(GR-PK to GR-OG)

Remove electronic switch

Signal for incorrect assembly - LED code (fast light 10Hz) -

Shut–off and locked out after 5 sec

Refit electronic switch to the mechanical sensor

Reset mains (5 sec)

Restart time delay 120 sec - LED code 1Hz

D7.8.3/0416/E 5/5

9 Wiring diagrams of OPS1 and OPS2

The electrical part of the OPS1 can be replaced by the OPS2 module. Please see connection diagram proposals

below.

9.1 5-wire connecting cable between electrical control panel and compressor terminal box

With a 5-wire connecting cable to the OPS module, one can duplicate the functions of the OPS1 with the OPS2.

9.2 7-wire connecting cable between electrical control panel and compressor terminal box

With a 7-wire connecting cable the full function range of the OPS2 can be used.

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