EMC Student Wiring Guide - the Georgia Agriculture Curriculum ...

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Table 250-66. Grounding Electrode Conductor for Alternating-Current
Systems
Size of Largest Ungrounded
Service-Entrance Conductor or
Equivalent Area for Parallel
Conductors (AWG/kcmil)
Copper
Aluminum or
Copper-Clad
Aluminum
2 or smaller 1/0 or smaller 8 6
1 or 1/0 2/0 or 3/0 6 4
2/0 or 3/0 4/0 or 250 kcmil 4 2
Over 3/0 Over 250 kcmil 2 1/0
through 350
kcmil
through 500
kcmil
Over 350 kcmil Over 500 kcmil 1/0 3/0
through 600
kcmil
through 900
kcmil
Over 600 kcmil Over 900 kcmil 2/0 4/0
through 1100 through 1750
kcmil
kcmil
4.3 EQUIPMENT GROUNDING:
Size of Grounding Electrode
Conductor (AWG/kcmil)
Copper
Aluminum or
Copper-Clad
Aluminum
Over 1100 Over 1750 3/0 250 kcmil
kcmil
kcmil
4.3.1 Metal raceways, cable trays, cable armor, cable sheath, enclosures,
frames, fittings and other metal non-current-carrying parts that are
to serve as grounding conductors with or without the use of
supplementary equipment grounding conductors shall be effectively
bonded where necessary to assure electrical continuity and the
capacity to conduct safely any fault current likely to be imposed on
them. Any nonconductive paint, enamel, or similar coating shall be
removed at threads, contact points, and contact surfaces or be
connected by means of fittings so designed as to make such
removal unnecessary. NEC 250.96
cover combination are listed as providing satisfactory ground
continuity between the box and the receptacle. NEC 250.146(A),
404.9, 404.9(B)(1)
4.3.4 Contact Devices or Yokes: Contact devices or yokes designed and
listed for the purpose shall be permitted in conjunction with the
supporting screws to establish the grounding circuit between the
device yoke and flush-type boxes. NEC 250.146(B)
4.3.5 Continuity and Attachment of Equipment Grounding Conductors to
Boxes: Where circuit conductors are spliced within a box, or
terminated on equipment within or supported by a box, any
equipment grounding conductor(s) associated with those circuit
conductors shall be connected within the box or to the box with
devices suitable for the use in accordance with NEC 240.148(A)
through (E). Connections depending solely on solder shall not be
used. Connections and splices shall be made in accordance with
NEC 110.14(B) except that insulation shall not be required. The
arrangement of grounding connections shall be such that the
disconnection or the removal of a receptacle, luminaire, or other
device fed from the box does not interfere with or interrupt the
grounding continuity. NEC 250.148, 250.148 (E), 250.148(A),
250.148(B).
4.3.6 Metal Boxes: A connection shall be made between the one or more
equipment grounding conductors and a metal box by means of a
grounding screw that shall be used for no other purpose, equipment
listed for grounding, or a listed grounding device. NEC 250.148(C)
4.4 GROUNDING ELECTRODE:
4.4.1 Grounding electrodes of rods of stainless steel and copper or zinc
coated steel shall be at least 5/8 inch (15.87 mm) in diameter unless
listed and not less than 1/2 inch (12.70 mm) in diameter. NEC
250.52(A)(5b)
4.4.2 Grounding electrodes of pipe or conduit shall not be smaller than
3/4 inch trade size (metric designator 21) and, where of steel, shall
have the outer surface galvanized or otherwise metal-coated for
corrosion protection. NEC 250.52(A)(5a)
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4.3.2 All receptacles installed on 15 and 20 ampere branch circuits shall
be of the grounding type NEC 406.3(A). General use snap switches
shall be effectively grounded. NEC 404.9(B)
4.3.3 Surface Mounted Box: When the box is mounted on the surface,
direct metal-to-metal contact between the device yoke and the box
or device that complies with 250.146(B) shall be permitted to
ground the receptacle and/or switch to box. At least one of the
insulating washers shall be removed from receptacles that do not
have a contact yoke or device that complies with 240.146(B) to
ensure direct metal-to-metal contact. This provision shall not apply
to cover-mounted receptacles and/or switch unless the box and
4.4.3 The electrode shall be installed such that at least 8 feet (2.44 m) of
length is in contact with the soil. It shall be driven to a depth of not
less than 8 feet (2.44 m) except that where rock bottom is
encountered, the electrode shall be driven at an oblique angle not to
exceed 45 degrees from the vertical or, where rock bottom is
encountered at an angle up to 45 degrees, the electrode shall be
buried in a trench that is at least 30 inches (750 mm) deep. The
upper end of the electrode shall be flush with or below ground level
unless the aboveground end and the grounding electrode conductor
attachment are protected against physical damage as specified in
NEC 250.10. NEC 250.53(G)