Service manual
Bonding
Ground Rods
4-3
4. Metallic mounting structures can be used as down conductors only if
electrically bonded to the scoreboard and ground rod.
1. Bonding to conductors can be made by welding, brazing or clamping
with at least two bolts, see Fig. 24A below.
2. Stranded cables can be installed with terminal lugs for ease of installa-
tion and to prevent fraying, see Fig 24B below.
Figure 24
3. When bonding copper to the aluminum scoreboard frame, a bi-metal
shim is needed to buffer the characteristics of dissimilar metals. This will
prevent harmful electrolytic action or the storage of charge between two
different elements, see Fig. 24C above.
4. Miscellaneous bonding hardware (see Fig. 24D) can be used for common
ground bonding.
At least one ground rod is required for each scoreboard module, except for
a bank of scoreboards. When a bank of scoreboards (a series of 3 or more
modules) are mounted together, two ground rods are required, one on each
side.
Before driving the ground rod into the soil, make sure there are no obsta-
cles beneath ground level where you have selected to install the rod.
Obstacles would include telephone lines, power lines, water pipes, gas
pipes, etc.
Select an installation position as close to the scoreboard as possible and
drive the 8 foot rod, two feet below the ground level, see Fig. 25 on the
following page.
Most installations will be done in moist clay-type soil; however, when grav-
elly or sandy conditions are encountered, additional ground rods would be
required at a minimum spacing of 10 feet, see Fig. 26 on the following
page. Where bedrock prevents rods from being driven to a 10 foot depth,
the conductor and rod should be laid in trenches horizontally not less than
12 feet at a depth of 1 or 2 feet in moist clay-like soil. For sandy or gravelly
conditions, the trenches should not be less than 24 feet in length and not
less than 2 feet in depth. Copper plates 0.032 inch thick and a two square
foot surface can be used where the soil is less than one foot deep.
Installation