14
OCH721A
8-4. M-NET WIRING METHOD
Points to notice:
(1) Outside the unit, transmission wires should stay away from electric wires in order to prevent electromagnetic noise from making
an influence on the signal communication. Place them at intervals of more than 5cm. Do not put them in the same conduit tube.
(2) Terminal block (TB7) for transmission wires should never be connected to 208/230 V power supply. If it is connected,
electronic parts on M-NET P.C. board may be burnt out.
(3) Use 2-core x AWG16 [1.25 mm
2
] shield wire (CVVS, CPEVS) for the transmission wire. Transmission signals may not be
sent or received normally if different types of transmission wires are put together in the same multi-conductor cable. Never
do this because this may cause a malfunction.
It is acceptable if M-NET wire (non-polar, 2-cores) is arranged in addition to the wiring for A-control.
(4) Ground only one of any appliances through M-NET transmission wire (shield wire). Communication error may occur due to
the influence of electromagnetic noise.
“Ed” error will appear on the LED display of outdoor unit.
“0403” error will appear on the centralized remote controller.
If there are more than 2 grounding spots on the shield wire, noise may enter into the shield wire because the ground wire and shield
wire form one circuit and the electric potential difference occurs due to the impedance difference among grounding spots. In the case
of single spot grounding, noise does not enter into the shield wire because the ground wire and shield wire do not form 1 circuit.
To avoid communication errors caused by noise, make sure to observe the single spot grounding method described in the
installation manual.
Centralized
controller
Refrigerant
address 00
M-NET
address 01
A-control
remote
controller
A-control
remote
controller
A-control
remote
controller
Refrigerant
address 00
M-NET
address 02
Refrigerant
address 00
M-NET
address 03
Power
supply unit
Centralized
controller
M-NET transmission wire
O
Bad example (Multi spot grounding of shield wire)
Good example 1 (Single spot grounding of shield wire)
Power
supply unit
M-NET type
outdoor unit
M-NET type
outdoor unit
M-NET type
outdoor unit
M-NET type
outdoor unit
M-NET transmission wire
M-NET type
outdoor unit
M-NET type
outdoor unit
M-NET type
outdoor unit
M-NET transmission wire
M-NET type
outdoor unit
M-NET type
outdoor unit
Good example 2 (Single spot grounding of shield wire)
Centralized
controller
Centralized
controller
Power
supply unit
Power
supply unit
●
M-NET wiring
(1) Use 2-core x AWG16 [1.25 mm
2
] shield wire for electric wires.
(Excluding the case connecting to system controller.)
(2) Connect the wire to the M-NET terminal block. Connect one core of the
transmission wire (non-polar) to A terminal and the other to B. Peel the
shield wire, twist the shield part to a string and connect it to S terminal.
(3) In the system which several outdoor units are being connected, the terminal
(A(M1), B(M2), S) on M-NET terminal block should be individually wired to the other
outdoor unit’s terminal, i.e. A to A, B to B and S to S. In this case, choose one of those outdoor units and drive a screw
to fix an ground wire on the plate as shown on the right figure.
Transmission
wire
Shield
part
M-NET
terminal
block
Ground
wire
A
B
S
