ERICO Practical Guide to Electrical Grounding - Manual (Page 68)

Practical Guide to Electrical Grounding
employ a system of double insulation which is distinctively
marked on the tool or appliance.
Receptacle Grounding. Since the early 1970s Section
210-7 of the NEC has required that all receptacles installed
on 15- and 20- ampere branch circuit be of the grounding
type. Grounding-type receptacles include provisions for
connecting an equipment grounding conductor and are
easily identifiable by the ground pin slot included in the
face of the receptacle. When installing grounding-type
receptacles the question often arises as to which way to
install the grounding pin, up or down? The NEC does not
address this but the most frequent practice is to install them
with the grounding pin down. A little thought, however,
gives a different perspective. For example, in cases where
the attachment plug is not fully inserted into the receptacle,
a greater degree of protection can be achieved by mounting
the receptacle with the grounding pin facing up. This is
because if a metal faceplate were to loosen and drop down
across the attachment plug blades or other metal objects
were to fall into the receptacle, they would most likely
make contact with the grounding pin, and not the energized
conductors. ERICO therefore believes that mounting
receptacles with the grounding pin up should result in the
safest possible installation. In installations where the
receptacle is mounted in the horizontal position, the
receptacle should be mounted with the neutral conductor
(long slot) up (Fig. 3-26). (Note: Several European
standards also require the grounding pin up.)
Other important requirements should be considered when
installing receptacles. Section 250-114 requires that the
equipment grounding conductors shall be terminated on the
receptacle in a manner that the disconnection of the
receptacle will not interrupt the continuity of the equipment
grounding conductor. This requirement results in the need
to splice all the equipment grounding conductors together
and take a “pigtail” off to the receptacle. A similar
requirement exists for the grounded conductor in multi-
wire branch-circuits. See the NEC Section 300-13 (b).
Another important installation practice for receptacles is
found in Section 410-56 (d). This section requires that
metal faceplates be grounded. All faceplates, when
installed, must completely cover the wall opening and seat
firmly against the mounting surface.
Section 410-56 (c) also contains provisions for installing
60
Fig. 3-26
Recommended
Not
Recommended
Fig. 3-27
Fig. 3-28
Ground bus may be floor mounted.
2700 Volt Insulators
Ground Bar,
Size As
Specified
Steel
Bracket
1/2" Silicon
Bronze
Hardware
1/4" x 2"
Copper
Bus Bar
Length As Specified
2700 Volt
Insulator
24" (TYP.)
Steel Bracket
6-1/4"
Grounding Book 4/14/99 10/5/99 6:01 PM Page 60 (Black plate)