Specifications
Table 10: Remote Field Bus Rules
Rules/LimitsCategory
When all of the devices connected on the Remote Field Bus are Metasys FACs, FECs,
VMA16s, or IOMs, the cable length limits (using 22 AWG 3-wire twisted, shielded cable) are
as follows:
• Each bus segment can be up to 1,520 m (5,000 ft) in length.
• Each RFB can be up to 4,750 m (15,000 ft) in length.
When one or more third-party family device is connected on the Remote Field Bus, the device
and bus segment limits are as follows:
•
Each bus segment can be up to 1,220 m (4,000 ft)
1
in length.
•
Each RFB can be up to 3,660 m (12,000 ft)
1
in length.
Note: Do not place slave devices on the Remote Field Bus. Slave devices on the Remote
Field Bus are not supported.
Cable Length for FC Bus and
Bus Segments
When using fiber-optic connections: 2,010 m (6,600 ft)
1
between two fiber modems.
BACnet Network Number assigned to the IP side of the Router must match the BACnet IP
network number used in the supervisory engines. The default IP network number is 1001.
Do not use 2000 or 65000 as the network number; these numbers are used for existing
embedded networks.
BACnet Network Number assigned to the MS/TP side of the BACnet Router must be unique
on the site across the entire BACnet Site. This may include multiple buildings, cities, states,
and even countries. It is very important to know the network to which you are adding one of
these routers.
Device Instance Number assigned to the BACnet Router must be unique on the site.
Network Number and Instance
Number for Router
Follow the manufacturers instructions to configure the BACnet Router’s IP address, BACnet
Device ID, MS/TP Network Number, and BBMD. Note that some routers do not have a device
object in which a device name and id is required.
Set Max Info Frames = 80 to 100 (all devices are Johnson Controls field devices) or 20 (some
or all devices are third-party field devices)
BACnet Router Settings
22 AWG Stranded, 3-Wire Twisted, Shielded Cable
Recommended Cable
2
The EOL switch must be set to On (or an EOL terminator installed) on the two devices located
at either end of each bus segment on a Remote Field Bus. Use an EOL terminator for the
BACnet Router as it has no EOL switch. The EOL switches must be set to Off (or EOL
termination disabled) for all other devices on the bus segment on a Remote Field Bus. See
EOL Termination on the Remote Field Bus for more information.
EOL Termination
1 If third-party devices are connected to the bus, the cable lengths should be reduced (if necessary) to match the third-party
vendor recommendations.
2
The recommended cable type provides the best bus performance. See MS/TP Bus Cable Recommendations for information
on alternative cable types and lengths that may be used in MS/TP applications.
32MS/TP Communications Bus Technical Bulletin