Application guidelines
16
FRCC.PC.021.A5.22
Electrical data, connections and wiring
Communication connections
In the case of parallel mounting, CAN-Bus cables
must link compressors together in order to
allow data exchange between compressors.
Connectors are 4 pole 0.14 inch pitch terminal
blocks.
In parallel mounting, only one HP transmitter and
one LP transmitter are needed per compressor
assembly, connected to only one of the OCS, for
the complete system.
If needed, the Modbus connection is to be done
with a 3 pole 0.14 inch pitch terminal block
(supplied on the OCS).
Shielded cables must be used for CAN-Bus and
Modbus connections.
A minimum distance of 4 inch between power
supply cables and communication cables
must be observed in order to avoid electronic
interferences and disturbances.
Accessory CAN-Bus cables and Modbus cables
are available for tandem and trio assemblies
(refer to accessories list for code numbers).
Data readings and recovering can be done thanks
to a MMIGRS and a MMIMYK connected on the
RJ11 female connection on the OCS (refer to
section “Data Management”).
MMIGRS and MMIMYK accessories are available
(refer to accessories list for code numbers).
OCS connections
The OCS comes preinstalled within the
compressor electrical box.
All needed connectors are plugged in place on
the OCS and connector positions are marked on
the transparent OCS protection cover.
The compressor comes with prewired OCS
connections for:
• discharge gas temperature sensor (DGT)
• surface sump heater (SSH)
• motor protection
• phase monitoring
• liquid injection valve (LIV)
Note that to avoid handling and transportation
issues, the discharge gas temperature cable is not
connected to the discharge temperature sensor
that is pre-installed on the upper shell. This
cable has to be connected to the sensor before
switching on the power.
Low pressure and high pressure transmitters
connection to the OCS are mandatory for
compressor operation (envelope monitoring).
Refer to “Pressure transmitter accuracy and range”
section.
LP and HP signals can also be transferred
via Modbus. Refer to “CAN-Bus and Modbus
communication with OCS” section for further
information.
HP and LP sensor connection
Shielded cable is mandatory for HP and LP sensor connections. Cable shield must be connected on
sensor side only.
High pressure sensor connection
Low pressure sensor connection
General wiring information
The wiring diagrams below are examples for a
safe and reliable compressor wiring. In case an
alternative wiring logic is chosen, it is imperative
to respect the following rules:
M1 M2 contact on OCS must be used for
compressor protection (do not use Bus signal).
When a safety switch trips, the compressor must
stop immediately and must not re-start until
the tripping condition is back to normal and
the safety switch is closed again. This applies to
the LP safety switch, the HP safety switch, the
discharge gas thermostat and the motor safety
thermostat.