Installation and Operations Guide
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Hardware installation
© Honeywell. All Rights Reserved. LT-VLXEXPAXMIOG Rev. 01
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Single-point grounding
Proper grounding is an essential element of trouble-free VLX/ACM-VLX/EXP/
AXM operation. Improper grounding is often the cause of communication
errors, analog and binary I/O inaccuracies, and even equipment damage.
Furthermore, the problems that result from improper grounding can be
intermittent and difficult to diagnose.
The single-point grounding shown in wiring diagrams and described in the
sections on power, communications, and I/O wiring is designed to minimize the
potential for problems associated with differences in ground potentials and
electrical transients (noise).
A single-point grounding practice, combined with separate 24 VAC power for
the BO loads (see Figure 13 on page 17), will help ensure an installation free
from problems related to improper grounding.
Panel ground
The panel you select to house the VLX/ACM-VLX and EXPs/AXMs must have
a ground bus that connects to a ground known to be suitable for this purpose. To
ground the panel bus, direct attachment to the closest point in the building’s
electrical service grounding electrode system is preferred. However, slight
variations in grounding practices may exist from one building to another.
Because of these variations, consulting with the building electrical contractor
about the best possible location and method to ground the panel bus is advised.
Once the panel bus is properly grounded, it can be used to terminate grounded
components of power, communications, and I/O wiring as shown in those
sections.
Ground lug on VLXs and EXPs
The ground lug on VLXs and EXPs must directly connect to panel ground using
stranded 12 AWG copper cable. When grounding, ensure that the cable is
properly positioned and secured. See Figure 16.
WARNING Do not over tightened the ground-lug screw. Excessive torque will
separate the terminal from the unit and cause the connection to fail.
Figure 16 VLX and EXP ground lug (GND) de tail
Ground screw
Termination platform
Circuit board
Warning!
Do not insert
ground cable here.
Insert ground cable here and
tighten screw to secure
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