8.3.2 Outdoor unit and indoor units’ P Q communication
Communication wiring design and installation should adhere to the following requirements:
0.75mm2 two-core shielded cable should be used for communication wiring. Using other types of cable can lead to
interference and malfunction.
Do not bind the communication line, refrigerant piping and power cable together.
The P Q communication wires should be connected one unit after another in a daisy chain from the outdoor unit to the
final indoor unit as shown in Figure 3-8.6. At the final indoor unit, a 120Ω resistor should be connected between the P
and Q terminals. After the final indoor unit, the communication wiring should NOT be continued back to the outdoor
unit – that is, do not attempt to form a closed loop.
The P and Q communication wires should NOT be connecting to E.
The shielding nets of the communication wires should be connected together and grounded. Grounding can be
achieved by connecting to the metal casing adjacent to the P Q E terminals of the outdoor unit electrical control box.
All IDUs in a system must be powered through a uniform power supply so that they can be powered on or off at the
same time
Applicable standards: EN 55014-1 and EN 55014-2. The communication line must be shielded wire.
RS-485(P Q) communication
L1+La+Ln≤1200m,Communication wiring 2*0.75mm
2
Communication wire
Power wire
P
Q
ODU
···
L1
La
P Q
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