Rs485 Installation And Set-Up; Rs485; Overview; Network Connection - Danfoss VLT HVAC Basic Drive FC 101 Design Manual

RS485 Installation and Set-...

7 RS485 Installation and Set-up

7.1 RS485

7.1.1 Overview

RS485 is a 2-wire bus interface compatible with multi-drop
network topology, that is, nodes can be connected as a
bus, or via drop cables from a common trunk line. A total
of 32 nodes can be connected to 1 network segment.
Repeaters divide network segments.
NOTICE
Each repeater functions as a node within the segment in
which it is installed. Each node connected within a given
network must have a unique node address across all
7 7
segments.
Terminate each segment at both ends, using either the
termination switch (S801) of the frequency converters or a
biased termination resistor network. Always use shielded
twisted pair (STP) cable for bus cabling, and follow good
common installation practice.
Low-impedance ground connection of the shield at every
node is important. Connect a large surface of the shield to
ground, for example with a cable clamp or a conductive
cable gland. Apply potential-equalizing cables to maintain
the same ground potential throughout the network -
particularly in installations with long cables.
To prevent impedance mismatch, always use the same
type of cable throughout the entire network. When
connecting a motor to the frequency converter, always use
shielded motor cable.
Cable
Impedance [Ω]
Cable length
[m (ft)]
Table 7.1 Cable Specifications
80
VLT
Screened twisted pair (STP)
120
Maximum 1200 (3937) (including drop lines).
Maximum 500 (1640) station-to-station.
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®
HVAC Basic Drive FC 101

7.1.2 Network Connection

Connect the frequency converter to the RS485 network as
follows (see also Illustration 7.1):
1. Connect signal wires to terminal 68 (P+) and
terminal 69 (N-) on the main control board of the
frequency converter.
2. Connect the cable shield to the cable clamps.
NOTICE
To reduce noise between conductors, use shielded,
twisted-pair cables.
Illustration 7.1 Network Connection
61 68 69
MG18C702