Rockwell Automation 1440-RMA00-04RC XM-440 Master Relay Module - Manual (Page 20)

Rockwell Automation Publication GMSI10-UM009D-EN-P - June 2011
20 Installing the XM-440 Master Relay Module
24V Common Grounding
24 V power to the XM modules must be grounded. When two or more power
supplies power the XM system, ground the 24 V Commons at a single point,
such as the ground bus bar.
DeviceNet Grounding
The DeviceNet network is functionally isolated and must be referenced to
earth ground at a single point. XM modules do not require an external
DeviceNet power supply. Connect DeviceNet V- to earth ground at one of the
XM modules, as shown in Figure 2.6.
Figure 2.6 Grounded DeviceNet V- at XM Module
IMPORTANT
If it is not possible or practical to ground the -24Vdc
supply, then it is possible for the system to be installed and
operate ungrounded. However, if installed ungrounded
then the system must not be connected to a ground
through any other circuit unless that circuit is isolated
externally. Connecting a floating system to a non-isolated
ground could result in damage to the XM module(s)
and/or any connected device. Also, operating the system
without a ground may result in the system not performing
to the published specifications regards measurement
accuracy and communications speed, distance or reliability.
IMPORTANT
The 24 V Common and Signal Common terminals are
internally connected. They are isolated from the Chassis
terminals unless they are connected to ground as described
in this section. Refer to Terminal Block Assignments on
page 25 for more information.
To
Ground
Bus