Daktronics DF-12xx - Manual (Page 14)

2-2 Electrical Installation
The contractor performing the electrical installation can verify ground resistance.
Technicians from Daktronics Sales and Service offices can also provide this service.
The display system must be connected to an earth electrode installed at the display.
Proper grounding is necessary for reliable equipment operation. It also protects the
equipment from damaging electrical disturbances and lightning. The display must
be properly grounded, or the warranty will be void. Refer to Drawing A-184918, for
information on where to connect the grounding wire. Connection at the driver
enclosure terminal block is illustrated at the bottom of the drawing.
The material for an earth-ground electrode differs from region to region and may
vary according to conditions present at the site. Consult the National Electrical Code
and any local electrical codes that may apply. The support structure of the display
cannot be used as an earth-ground electrode. The support is generally embedded in
concrete, and if it is in earth, the steel is usually primed or it corrodes, making it a
poor ground in either case.
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 circuit 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. The
National Electrical Code requires the use of a lockable power disconnect within
sight of or at the display.
Installation with Only a Neutral Conductor Provided
Installations where no grounding conductor is provided must comply with Article
250-32 of the National Electrical Code. If the installation in question meets all of the
requirements of Article 250-32, the following guidelines must be observed:
• Connect the grounding electrode cable at the local disconnect, never at the
display driver/power enclosure.
• Use a disconnect that opens all of the ungrounded phase conductors.
2.3 Lightning Protection
The use of a disconnect near the display to completely cut all current-carrying lines
significantly protects the circuits against lightning damage. The National Electrical
Code also requires it. In order for this device to provide protection, the power must
be disconnected when the display is not in use. The control console should also be
disconnected from power and from the signal j-box when the system is not being
used. The same surges that may damage the display's driver can also damage the
driver console's circuit.