Distech Controls RS485 Installation Manual page 5

Prerequisite: Nearby earth grounding point.
1. Install the included earth ground wire to the option module's earth ground spade lug and terminate the other end to a nearby earth ground.
2. The EC-BOS's earth ground spade lug should also be terminated to earth ground. This also applies to any other option module with a ground spade
lug.
RS485 Wiring
Each of the two RS485 ports is capable of up to 115,200 baud, and uses a 3-position, removable, screw terminal connector.
Use shielded, twisted-pair, 18-22 AWG cabling to wire in a continuous multidrop fashion to other RS485 devices: "minus to minus", "plus to plus", and
"shield to shield".
Connect the shield wire to earth ground at one end only, for example at the option module. The figure below shows an example of RS485 wiring.
RS485-A port COM n with a network of RS485 devices.
1
RS485-A port COM n+1 with a network of RS485 devices.
2
3 RS485 devices on the same network should use the same protocol and baud rate. Up to 32 or more devices may be supported,
depending on device specifications.
RS485 Bias Switches
Each RS485 port has an adjacent 3-position biasing switch.
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