ERICO Practical Guide to Electrical Grounding - Manual (Page 59)

comprise the grounding electrode system. While these
guidelines may appear to be somewhat vague, a good rule
of thumb to follow is: If the interior metal piping system
contains any electrical devices, such as, solenoids or
mechanized valves, the piping “may become energized”
and it should be bonded.
The last part of Section 250-80 contains a new requirement
in the 1996 NEC. This section requires that any exposed
structural steel which is interconnected to form a building
frame and is not intentionally grounded shall be bonded.
Once again this steel must be bonded only if it “may
become energized.” Installers and designers of electrical
systems should recognize that there are many ways the steel
“may” become energized by equipment which may be
mounted to or in contact with the steel. For this reason the
recommended course is to make the bond. As both cases
above, the permissible bonding locations are to the service
equipment enclosure, the grounding electrode conductor,
the service grounded conductor or to the one or more
grounding electrodes that comprise the grounding electrode
system. This requirement does not apply to isolated steel
girders or beams which may be installed in a building or
structure. Such beams or girders are not “interconnected to
form a steel building frame” and need not be bonded.
Article 680 Bonding. One last area that should be of great
concern for designers and installers of bonding and
grounding systems is Article 680 of the NEC. Because of
the constant presence of moisture, installations in and
around swimming pools, fountains, spas and similar
locations present an increased risk of electrical shock.
Section 680-22 covers the bonding requirements for
permanently installed swimming pools. For all permanently
installed pools the following components must be bonded
together:
1. All metal parts of the pool, including the pool
structure, shell, coping stones and deck.
2. No-niche fixture forming shells and mounting
brackets.
3. All metal fittings associated with the pool structure.
4. All metal parts of any electric equipment associated
with the pool filtering or circulating system.
5. All metal parts of any equipment associated with
pool covers.
6. Metal-sheathed cables, raceways, metal piping and
all other metal components that are located in a
zone which extends from the edge of the pool to a
distance which is 5 ft (1.5 m) horizontally and 12 ft
(3.7 m) above the maximum water level of the pool.
Included also would be any diving structures,
observation decks, towers, etc., which are not
separated from the pool by a permanent barrier.
It is interesting to note that a FPN which precedes these
requirements states that it is not the intent that the copper
conductor which is used to interconnect these components
be extended or otherwise attached to any remote
panelboard service equipment or grounding electrode. This
note clearly distinguishes the difference between bonding
and grounding. The purpose of these requirements is to
bond all of the metal components listed above together, to
establish a common bonding grid. The common bonding
grid establishes an equipotential plane which minimizes
any difference of potential between any of the common
components. Without a difference of potential there can be
no risk of electrical shock. Part (b) of Section 680-22
requires that the common bonding grid be connected with
at least a No. 8 copper conductor. Installers should note that
the means of connection must be by pressure connectors or
clamps or CADWELD exothermic connections. Care
should be taken to ensure that the connectors selected are
suitable for direct burial applications and with the type of
material used (copper, aluminum etc.). Section 680-41 (d)
contains similar requirements for bonding for spas and hot
tubs. In either case, bonding is critical to protecting
personnel who might be exposed to an electrical shock
hazard if the low impedance bonding grid is not
maintained. ERICO offers a complete line of connectors
which can be used to ensure the common bonding grid is
installed in a manner which ensures the safety of anyone
using the pools, hot tubs or spas.
BUILDING INTERIOR BONDS
The interior columns and beams with riveted or bolted
construction joints may require positive bonding of beams
to columns to provide long term low resistance joints for
electrical continuity throughout the building (Fig. 3-1). The
low resistivity also may be achieved if all columns through
their footers are bonded together. Welding a ground bar to
the column provides future attachment points for other
grounding conductors (Fig. 3-2). At expansion joints, a
flexible conductor bonds the columns or beams on each
side of the joint (Fig. 3-3). The bottom chord of a bar joist
easily can be bonded (Fig. 3-4). Steel columns within the
building should be bonded to the footer with the conductor
extending to the main ground grid (Fig. 3-5 and Fig. 3-6).
The column anchor bolts must be electrically connected to
the footer reinforcing bars.
On multi-floor buildings, the grounding conductor should
51 Chapter 3: Building Interior Bonding & Grounding
Grounding Book 4/14/99 10/5/99 6:01 PM Page 51 (Black plate)