29
Electrical Installation
2.Instructions on ground terminal of 485 control line
It is forbidden to connect to the strong current 220V ground terminal for the metal plate of the electric cabinet.
485 grounding port G is the ground terminal for DC power supply of the electric control board.
3.Installation requirements of 485 communication line
• Requirements of communication line: RS485 wire must be AWG # 18
～
22 wire with the wire diameter more than 0.75mm
2
,and be a twisted
pair with a shielding layer and twist pitch not more than 5cm.
• Hand-in-hand connection requirements: each system module is equipped with two terminals
A and B for RS485 connection. In addition to two terminals A and B, the outdoor unit module also has a terminal G for connecting the shield
-
ing layer of the communication line. The shielded twisted pair must be connected hand in hand, and no star connection shall be allowed,
namely, 1 is connected to 2, 2 is connected to 3, and 3 is connected to 4;
If 1 is connected to 2, 2 is connected to 3, and 2 is connected to 4, that connection will be wrong.
• Wiring requirements of shielding layer: after being twisted, the shielding layer shall be wrapped with adhesive tape to prevent it from being
connected with 220Vground. One end of the shielding layer shall be connected to the ground point G of the control cabinet for the outdoor
unit. When the outdoor unit module is connected, the shielding layer shall be connected to the terminal G.It is forbidden to connect it to the
220V ground terminal of the metal plate for the electric cabinet
.
• When the network is unstable, 120ohms and 1uFnetwork terminal resistors connected in series shall be added and installed on the communication
ports A and B of the last unit on the network in parallel.
