Cabling - Danfoss DriveMotor FCP 106 BACnet Operating Instructions Manual

Installation

3.1.3 Cabling

Cable lengths and number of nodes
For the correct function of a BACnet MS/TP system, it is mandatory to fulfill installation of the communication cables given
in this manual. Under correct installation it is possible to have up to 250 nodes (125 masters and 125 slaves) on 1,200 m
(4,000 ft) cable.
The use of drop cable connection (i.e. T-connection) is not allowed in a BACnet MS/TP system. Drop cables lead to reflection
and malfunction of the system. In locations where the cabling demands a T-connection the use of repeaters is
recommended.
NOTICE
A repeater is a node in each of the 2 segments it connects. The number of frequency converters is based on a single
master system. If there are 2 or more devices (e.g. PC tools, Routers), reduce the number of frequency converters
correspondingly.
•
Maximum length of an MS/TP segment: 1,200 m (4,000 ft)
•
Characteristic impedance: 100 to 130 Ω
•
Resistance: <110 Ω/km
•
Distributed capacitance: <100 pF/m, between conductors
•
Cross section: 0.82 mm
•
Cable type: twisted in pairs, 1 x 2, or 2 x 2 wires
•
Screening: Copper-braided screen or braided screen and foil screen
NOTICE
Use of the same cable type throughout the entire segment is recommended to avoid impedance mismatch.
Illustration 3.1 BACnet Interface
®
VLT DriveMotor FCP 106 & FCM 106 BACnet Operating Instructions
2
conductor area, corresponding to AWG 18
MG03O102 - Danfoss A/S © 12/2013. All rights reserved.
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