Operation Manual

Protect PV.250 Operating Instructions
Page 29 of 51 80000027023 BAL, en
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 required, insert the 120R resistor supplied be-
tween 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 shield:
• 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.
• Route the shield on a shield busbar directly from where the line
enters the cubicle. Route 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 sev-
eral bus stations are present, you must make sure that the shield
is never interrupted.
Please always attach the shield of the RS485 bus line to earth on
the quiescent side, i.e. only one side of the shield is attached to
earth 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 unit until it reaches the Mul-
tiCom interface, shorten it accordingly and attach both wires to
terminals A and B.