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Protect PV.500-MH Operating Instructions 
46 of 68 
80000043212 BAL 
 
Figure 15 
Serial D-sub connector X5 
Port 2 (X5): RS485 pin assignment (default) 
Pin number  Signal Description 
3 B 
High 
data 
8 A 
Low 
data 
Housing 
 
INV housing potential 
 
Please use a shielded fieldbus cable as the line, 
e.g. 2 x 0.22 twisted pair Lapp "UNITRONIC-BUS LD". 
 
Please connect the RS485 bus line via the bus interface connector 
supplied. In an RS485 network, the ends of the bus must always 
be terminated. If necessary, insert the 120 ohm resistor supplied 
between connections A and B. 
Shield connection of the RS485 bus line: 
Shielding
 is a means of weakening (attenuating) magnetic, elec-
trical or electromagnetic interference fields. 
Interference currents on line shields are dissipated to earth by 
means of the shield busbar that has a conductive connection to the 
housing. A low-impedance connection to the PE conductor is es-
pecially important to prevent these interference currents from 
themselves becoming a source of interference. 
If possible, only use lines with a braided shield. The shield cover-
age should be at least 80%. Avoid using lines with a foil shield be-
cause tensile and compressive stresses applied when fastening 
the line can easily damage the foil, resulting in a reduction in the 
shielding effect. 
Please bear the following points in mind when handling the screen: 
  Use cable clips or shield terminal blocks made of metal to se-
cure the braided shield. The clips must surround the shield and 
make good contact with it over a large area. 
  Attach the shield to a shield busbar right after the line enters 
the cabinet. Run the shield right up to the assembly; however, 
ensure that it does not make contact there! 
When used in PV applications, the shield of the RS485 bus line 
should only be earthed on one side so that no equalising or inter-
ference currents can flow through the shielding. However, if sever-
al bus stations are present, you must make sure that the shield is 
never interrupted. 
 
Always attach the shield of the RS485 bus line to earth on the qui-
escent side, i.e. only one side of the shield is attached to the earth 
potential on the master or data logger side. 
In the PV inverter, the shield must not be connected to the housing 
in any way. 
Insert the RS485 bus cable into the equipment until it reaches the 
MultiCom interface, shorten it accordingly and attach both wires to 
terminals A and B.