Trane TR200 Operating Instructions Manual page 9

Embedded bacnet

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How to Install

The BACnet Interface

Cabling

Cable lengths and number of nodes

The maximum cable length allowable in one segment is dependent on the transmission speed. The total cable length

includes drop cables if any. A drop cable is the connection from the main bus cable to each node.

Drop cable connection (i.e. T-connection) is not recommended, due to the increased risk of reflection occurring. Instead,

Trane recommends direct connection of the frequency converter.

Note that a repeater is a node in both of the two segments it connects. The number of frequency converters is based on a

single

system. If there are two or more devices (e.g. PC tools, Routers), the number of frequency converters must be

reduced correspondingly.

Maximum length of an

Impedance: 100 to 130 Ohm

Resistance: <110 Ohm/km

Capacitance: <100 pF/m

Distributed capacitance between conductors and shield shall be less that 200 pF per meter

Cross section: 0.82 mm 2 conductor area, corresponding to AWG 18

Cable type: twisted in pairs, 1 x 2, or 2 x 2 wires

Screening: Copper-braided screen or braided screen and foil screen

Use of the same cable type throughout the entire segment is recommended to avoid impedance mismatch.

Network Connection

Connect the frequency converter to the RS-485 network as follows (see also diagram):

Connect signal wires to terminal 68 (P+) and terminal 69 (N-) on the main control board of the frequency converter.

Connect the cable screen as described under chapter Bus Cabling.

Note

Screened, twisted-pair cables are recommended in order to reduce noise between conductors.

TP segment: 1200 meters (4000 feet)

TR200 Embedded BACnet Operating Instructions