Quantcast Table 1-20. Grounding Electrode Conductor Size

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MIL-HDBK-419A
Table 1-20. Grounding Electrode Conductor Size
Size of Largest Service-Entrance
Minimum Size of Grounding
Conductor or Equivalent for
Electrode Conductor
Parallel Conductors (AWG)
(AWG)
Aluminum or
Aluminum or
Copper-Clad
Copper-Clad
Aluminum1
Copper
Aluminum
Copper
2 or smaller
0 or smaller
8
6
2/0 or 3/0
6
1 or 0
4
4
4/0 or 250 MCM
2
2/0 or 3/0
Over 250 MCM
2
0
Over 3/0 thru
350 MCM
thru 500 MCM
Over 350 MCM
0
Over 500 MCM
3/0
thru 600 MCM
thru 900 MCM
Over 600 MCM
Over 900 MCM
2/0
4/0
thru 1100 MCM
thru 1750 MCM
3/0
Over 1100 MCM
Over 1750 MCM
250 MCM
NOTE: Where the service conductors or the equivalent size of parallel conductors exceed 1100 MCM, the size
of the grounding electrode conductor shall not be less than 12-l/2 percent of the area of the service
conductor(s).
`Aluminum or copper-clad aluminum grounding conductors shall not be used where in direct contact with
masonry or the earth or where subject to corrosive conditions. Where used outside, aluminum or copper-clad
aluminum grounding conductors shall not be installed within 45 cm (18 inches) of the earth.
(b)  The source can be grounded such that the maximum voltage to ground on the ungrounded
conductors does not exceed 150 volts.
(c)  Where the source is nominally rated 480/277-volt, 3-phase, 4-wire wye in which the
midpoint of one phase is used as a circuit conductor.
(d)  Where the source is nominally rated 240/120-volts, 3-phase, 4-wire wye in which the
midpoint of one phase is used as a circuit conductor.
(e)
Where a grounded service conductor is uninsulated.
(2)  Where a source is grounded, verify that the installation complies with 1.4.9.2b(1). Also see
Article 250-26 of the NEC.
1-107





 


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