Using Repeaters To Extend The Data Bus - Acuity Controls nLight ECLYPSE User Manual

BACnet MS/TP Communication Data Bus Fundamentals
Typical BACnet 24VAC-
Powered Controller
Data Bus Shield:
Isolate with
electrical tape
Figure 96: Typical Cable-Shield Grounding Requirements for a BACnet MS/TP Data Bus Segment with an ECLYPSE Controller located
in the Middle of the Data Bus

Using Repeaters to Extend the Data Bus

A BACnet MS/TP data bus segment can be up to 1220 meters (4000 feet) long with up to a maximum of 50 devices. When
a greater length is required, a solution is to use a repeater. A repeater increases the maximum length of the data bus.
Using a Repeater to Extend the Length of the BACnet MS/TP Data Bus
Repeaters can be used to extend a BACnet MS/TP data bus up to 3660 meters maximum total length. Do not use more
than two repeaters on a BACnet MS/TP LAN.
A BACnet MS/TP repeater is a bi-directional device that regenerates and strengthens the electrical signals that pass
through it. It creates two electrically-isolated BACnet MS/TP data bus segments that transparently enable devices on one
side of the repeater to communicate with any device on the other side. The two BACnet MS/TP data bus segments have
the same requirements of an ordinary BACnet MS/TP data bus segment; that is, each BACnet MS/TP data bus segment:
Can be up to 1220 meters (4000 feet) long.
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The first and last device on the data bus must have End-of-Line (EOL) termination resistors connected across the two
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data lines/wires of the twisted pair.
Must respect the maximum limit for
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Will have the same network number as they remain part of the same network or LAN.
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It is recommended that you connect no more than 50 ⅛ or ½-load devices on all BACnet MS/TP Data Bus repeater seg-
ments when a baud rate of 19 200 or higher is used (preferably 38 400 baud). This is to ensure that the BACnet MS/TP
Data Bus has enough bandwidth to efficiently communicate network variables between controllers.
Do not use more than two repeaters on a BACnet MS/TP data bus.
A repeater can only connect two BACnet MS/TP data bus segments even if it has ports to support more than two BACnet MS/TP data bus
segments.
A repeater can be added anywhere to a data bus segment including the end of the segment as shown below.
nLight ECLYPSE
Typical BACnet 24VAC-
Powered Controller
Data Bus Shields: Twist
together and Isolate
with electrical tape
Device Loading.
ECLYPSE
Data Bus Shields:
Connect to the 'S'
terminal
Data Bus Shields: Twist
together and Isolate
with electrical tape
Data Bus: Shielded Twisted Pair Cable
Electrical The shield of the data bus must be connected to
System
Ground
Typical BACnet 24VAC-
Powered Controller
Data Bus Shield:
Isolate with
electrical tape
the electrical system ground at one point only –
usually at the Building Controller, when present
Typical BACnet 24VAC-
Powered Controller
98