En-3
ELECTRICAL WIRING
General-purpose building
control computer
(MODBUS device)
TRANSMISSION CABLE
OUTDOOR UNIT
MASTER OR SLAVE
OUTDOOR UNIT
INDOOR UNIT
Power supply
cable
MODBUS cable
Transmission cable
to VRF network
MODBUS CONVERTOR
SWITCH
(Disconnect
switch)
FUSE (2A)
1Ø 50/60 Hz
208-240 V
MODBUS
CABLE
POWER
SUPPLY
CABLE
Note :
• Do not bind the power supply cable and transmission cable to avoid an
erroneous operation.
• Use shield cable for transmission cable.
The shield metal should be earthed (grounded).
• Do not forget to earth (ground) the MODBUS Convertor.
• Install the disconnect switch to the easily accessible location.
• Install the fuse (2A) to the L (L1) line of power supply cable.
• Before connecting cables, turn off the power of the VRF units connected
to the convertor.
6.2. Unit wiring
6.2.1. Power supply cable
Keep the ground cable longer than the other cables.
Power supply cable
25m
m
(1in
)
Earth (Ground)
cable
15m
m
(9/1
6 in
)
(1) Use ring terminals with insulating sleeves as shown in the figure below
to connect to the terminal block.
(2) Securely clamp the ring terminals to the cables using an appropriate
tool so that the cables do not come loose.
(3) Use the specified cables, connect them securely, and fasten them so
that there is no stress placed on the terminals.
(4) Use an appropriate screwdriver to tighten the terminal screws.
Do not use a screwdriver that is too small, otherwise, the screw heads
may be damaged and prevent the screws from being properly tight-
ened.
(5) Do not tighten the terminal screws too much, otherwise, the screws
may break.
(6) See the table for the terminal screw tightening torques.
(7) Do not fix 2 or more power supply cables with 1 screw.
6.1. Wiring method
PROPER SYSTEM DIAGRAM
MODBUS Network
Indoor unit
VRF network system
Outdoor unit
Lighting facilities
Security system
Automatic fire
alarm interface
Ventilation system
General-purpose
MODBUS master unit
(MODBUS device)
MODBUS
Convertor
(UTY-VMGX)
VRF
Outdoor unit
Indoor unit
Transmission cable
(non-polar
2-conductor)
Maximum controllable indoor unit
number per 1 MODBUS Convertor
128
Maximum controllable outdoor unit
number per 1 MODBUS Convertor
100
Maximum connectable MODBUS
Convertor number per 1 VRF System
9
Maximum number of connected
MODBUS Convertor units to one
MODBUS master unit
Without repeater
31
With repeater
247*
* Due to the limit in the number of slave addresses
