Daktronics AF-3180-64-R,A - Manual (Page 26)

Figure 20: Display Grounding
A minimum of one grounding electrode must be installed for each display face. The
grounding electrode is typically one grounding rod for each display face. Other
grounding electrodes as described in Article 250 of the National Electric Code may
be used. Daktronics requires that the resistance to ground be 10 ohms or less. If the
resistance to ground is higher than 10 ohms, it will be necessary to install additional
grounding electrodes to reduce the resistance. The grounding electrode should be
installed within 25 feet of the base of the display. The grounding electrode must be
connected to the ground terminal in the display power term panel.
This grounding electrode must be installed in addition to the equipment-grounding
conductor that should be part of the power installation. The material of an earth-
ground electrode differs from region to region and because of conditions present at
the site.
The support structure of the display cannot be used as an earth ground electrode. The
support is generally embedded in concrete, and if in earth, the steel is either primed
or it corrodes, making it a poor ground. The grounding system and grounding
electrodes must be installed according to Article 250 of the National Electrical Code
and any applicable local codes.
Power Installation
There are two considerations for power installation: installation with ground and
neutral conductors provided and installation with only a neutral conductor provided.
These two power installations differ slightly, as described in the following
paragraphs:
Installation with Ground and Neutral Conductors Provided
For this type of installation, the power cable must contain an isolated earth-ground
conductor. Under this circumstance, do not connect neutral to ground at the
disconnect or at the display. This would violate electrical codes and void the
warranty. Use a disconnect so that all hot lines and neutral can be disconnected.
Refer to Figure 20 below for installation details. The National Electrical Code
requires the use of a lockable power disconnect within sight of or at the display.
Electrical Installation 3-6