BACnet MS/TP Communication Data Bus Fundamentals
Network Guide 27
Figure 14: Typical Cable-Shield Grounding Requirements for a BACnet MS/TP Data Bus Segment with a Building
Controller located in the Middle of the Data Bus
Figure 15: Typical Cable-Shield Grounding Requirements for a BACnet MS/TP Data Bus Segment without
Building Controller
Typical BACnet 24VAC-
Powered Controller
Data Bus Shields: Twist
together and Isolate
with electrical tape
Typical BACnet 24VAC-
Powered Controller
Data Bus: Shielded Twisted Pair Cable
NET+
NET-
NET+
NET-
Typical BACnet 24VAC-
Powered Controller
NET+
NET-
Data Bus Shield:
Isolate with
electrical tape
Typical BACnet Line-
Powered Controller
Data Bus Shields: Twist
Together and Connect
to ‘COM’ Terminal
NET-
NET+
COM
Typical BACnet Line-
Powered Controller
Data Bus Shields:
Connect to ‘COM’
Terminal
NET-
NET+
COM
Electrical
System
Ground
The shield of the data bus must be connected to
the electrical system ground at one point only ,
ideally in the middle of the data bus as shown
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