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Installation
Wiring CTs
46
Building Technologies
125-202
06/06/2017
WARNING
At this time, DO NOT connect the communication cable to the communication trunk.
Doing so may damage communication devices or cause personal injury.
WARNING
USE ONLY SHUNTED CURRENT TRANSFORMERS (CTs). DO NOT USE 5A
SECONDARY CTs OR UNSHUNTED CTs.
Do not use other CTs. Only use shunted CTs with a 333 mV maximum output.
Serious shock hazard and meter damage can occur if unshunted CTs are used. Only
use Siemens Industry Inc‘s CTs that are UL listed/Recognized and have been
evaluated to IEC61010-1.
2. Remove the black RS-485 connector from the MD-BMS or MD-BMED Power Meter
and wire the communication cable to the RS-485 connector. Connect positive (+),
and negative (-) wires to the RS-485 connector using the daisy-chain method (see
figure below). Keep length of exposed wire to a minimum.
3. Connect the COMMON wire to the RS-485 connector (S) terminal (see figure
below).
4. Tape back one of the communication cable shields and connect the other shield to
the Utility Panel Ground.
5. If the MD-BMS or MD-BMED is the last networked device, install the end of line
terminator on the positive (+) and negative (-) terminals.
6. Tape or shrink wrap all communication wire terminations and insulate any other
exposed communication wiring. Ensure that insulation complies with local and
National Electrical Codes.
7. Plug the terminal block back into the MD-BMS or MD-BMED Power Meter and
mechanically secure the communication wire terminations to the power meter to
prevent accidental removal.
Figure 8: Connecting and Insulating Communication Cable on MD-BMS or MD-BMED RS-485
Connector.