ERICO Practical Guide to Electrical Grounding - Manual (Page 24)

16 Practical Guide to Electrical Grounding
each end of the enclosure or raceway to the grounding
conductor. IEEE paper No. 54 and other studies have shown
that, in cases where such bonding is omitted, the impedance
of the conductor is approximately doubled. Bonding in
these cases is essentially to ensure proper operation of the
grounding electrode system. Bonding can be accomplished
by connecting each end of the GEC enclosure or raceway to
the electrical equipment enclosure and the actual electrode.
Section 250-79 (d) requires that the size of the bonding
jumper for GEC raceways or enclosures be the same size or
larger than the enclosed grounding electrode conductor
(Fig. 1-39). Another possible solution to protecting the
grounding electrode conductor from physical damage is to
use a nonmetallic raceway. Such raceways are permitted
and, because they are constructed of nonmetallic materials,
they do not require bonding (Fig. 1-40).
Occasionally during construction, a grounding conductor
may be damaged where it is stubbed through the concrete.
Installers should note that ERICO features a full line of
CADWELD connections that can be used to repair the
conductor without any loss of capacity in the conductor.
Repair splices are available for both horizontal and vertical
conductors. A minimum amount of concrete may need to be
chipped away in order to make the splice (Fig. 1-41).
Installers may also encounter applications where the GEC
needs to be extended to a new service location or for a
modification to the electrical distribution system. Section
250-81 Exception No. 1 permits the GEC to be spliced
by means of irreversible compression-type connectors
listed for this use or by the exothermic welding process.
CADWELD offers a complete line of connections
suitable for splicing the full range of grounding
electrode conductors.
All of these components, when installed, comprise the
grounding electrode system for the building or structure
served. All of these must be bonded together and when they
are installed where multiple grounding systems are present,
such as lightning protection systems, they shall be installed
at a point which is not less than 6 ft (1.8 m) from any other
electrode of another grounding system. Section 250-54
requires that when an AC system is connected to a
grounding electrode system, as described above, the same
electrode shall be used to ground conductor enclosures and
equipment in or on that building. Separate grounding
electrode systems are not permitted within the same
building. In the event that a building is supplied by two or
more services as permitted by Section 230-2 Exceptions,
the same grounding electrode system shall be used. Two or
more electrodes which are bonded together are considered
a single grounding electrode system.
Contractors must understand that these grounding
connections are critical to the overall electrical power distri-
bution system and they must take great care when they
make these connections.
Bonding Jumper,
2/0 or Larger
Electrical
Service
Panelboard
Grounding
Electrode
Conductor
Main Bonding
Jumper
Neutral
Ground Bus
Building Steel
CADWELD Connections
Metal Raceway
2/0 GEC
Fig. 1-39
Fig. 1-40
Support
Strap
Wall or
Column
(Typ.)
Max. 6"
Bare Copper Ground Wire
#6 AWG and Larger Note 2
3/4" Schedule 80-PVC
Conduit
Support Strap (Typ)
Grade or Floor
8'-0" Minimum
Grounding Book 4/14/99 10/5/99 6:01 PM Page 16 (Black plate)