BACnet MS/TP Communication Data Bus Fundamentals
Network Guide 47
ECx-4XX I/O Extension Module Power Supply
Requirements
When an ECB-600 is used with one or more ECx-4XXs (I/O Extension Modules), always use a
separate transformer for each ECB-600 series controller and for each of its associated I/O
Extension Modules. See Transformer Selection and Determining the Maximum Power Run
Length on page 43 for how to choose an appropriate transformer. One terminal on the second-
ary side of each of these transformers must be connected to the building's ground and to the
respective controller's or I/O Extension Modules' 24V COM terminal. See Figure 29.
Note that the shield of the 2-Wire subnetwork data bus cable must also be grounded, prefera-
bly at the ECB-600. See also 2-Wire Subnetwork Data Bus Shield Grounding Requirements
on page 94.
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