Distech ECYPSE - Using Repeaters to Extend the Data Bus

BACnet MS/TP Communication Data Bus Fundamentals
122 ECLYPSE User Guide
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.
 The first and last device on the data bus must have End-of-Line (EOL) termination
resistors connected across the two data lines/wires of the twisted pair.
 Must respect the maximum limit for Device Loading on page 113.
 Will have the same network number as they remain part of the same network or LAN.
Distech Controls recommends that you connect no more than 50 of our ⅛ or ½-load devices
on all BACnet MS/TP Data Bus repeater segments 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.
MS/TP Data Bus:
- 3660 m (12 000 ft) Maximum Total
- 50 Connected Devices Maximum Total
MS/TP Data Bus Segment:
- 1220 m (4 000 ft) Maximum
MS/TP Data Bus Segment:
- 1220 m (4 000 ft) Maximum
MS/TP Data Bus Segment:
- 1220 m (4 000 ft) Maximum
< 7.6 m
< 25 ft
MS/TP
Repeater
EOL Terminators
MS/TP
Repeater
EOL Internally Set EOL Internally Set
< 7.6 m
< 25 ft
EOL
ON
EOL
ON
EOL
ON
EOL Internally Set
ECY-S1000
EOL Internally Set
EOL
ON
Figure 11-12: Using a Repeater to Extend the Range of the LAN