Chapter 3 Wiring Methods and Materials

ARTICLE 31O-CONDUCTORS FOR GENERAL WIRING
310.15
Table 310.13(E) Thickness of Insulation for Shielded Solid Dielectric Insulated Conductors Rated 2001 to 35,000 Volts
2001-5000
....
Volts 5001-8000 Volts 8001-15,000 Volts 15,001-25,000 Volts
100 133 173 100 133 173 100 133 173
• Percent
MPJ'
Percent Percent Percent Percent Percent Percent Percent Percent
Conductor Insulation Insulation Insulation Insulation Insulation Insulation Insulation Insulation Insulation
Size ~J ,c··" .. ;
Levell Level 2 Levee Levell Level 2 Level 3 Levell Level 2 Level 3
(AWG
or kcmil) mm mils mm mils mm mils mm mils mm mils mm mils mm mils mm mils mm mils mm mils
8 2.29 90
6-4 2.29 90 2.92 115 3.56 140 4.45 175
2 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260
1 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260 6.60 260 8.13 320 10.67 420
1/0-2000 2.29 90 2.92 115 3.56 140 4.45 175 4.45 175 5.59 220 6.60 260 6.60 260 8.13 320 10.67 420
25,001-28,000 volts 28,001-35,000 volts
Conductor
Size
(AWG
or kcmil)
100
Percent
Insulation
Levell
mm
mils
133
Percent
Insulation
Level 2
mm
mils
173
Percent
Insulation
Level 3
mm
mils
100
Percent
Insulation
Levell
mm
mils
133
Percent
Insulation
Level 2
mm
mils
mm
173
Percent
Insulation
Level 3
mils
1
1/0-2000
7.11
7.11
280
280
8.76
8.76
345
345
11..30
11.30
445
445 8.76 345 10.67 420 14.73 580
1100 Percent Insulation Level. Cables in this category shall be pennitted to be applied where the system is provided with relay protection such
that ground faults will be cleared as rapidly as possible but, in any case, within 1 minute. While these cables are applicable to the great majority
of cable installations that are on grounded systems, they shall be permitted to be used also on other systems for which the application of cables is
acceptable, provided the above clearing requirements are met in completely de-energizing the faulted section.
2133 Percent Insulation Level. This insulation level corresponds to that formerly designated for ungrounded systems. Cables in this category shall
be permitted to be applied in situations where the clearing time requirements of the 100 percent level category cannot be met and yet there is
adequate assurance that the faulted section will be de-energized in a time not exceeding I hour. Also, they shall be permitted to be used in
100 percent insulation level applications where additional insulation is desirable.
3173 Percent Insulation Level. Cables in this category shall be permitted to be applied under all of the following conditions:
(I) In industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation
(2) Where the fault clearing time requirements of the 133 percent level category cannot be met
(3) Where an orderly shutdown is essential to protect equipment and personnel
(4) There is adequate assurance that the faulted section will be de-energized in an orderly shutdown
Also, cables with this insulation thickness shall be permitted to be used in 100 or 133 percent insulation level applications where additional
insulation strength is desirable.
310.14 Aluminum Conductor Material. Solid aluminum No.4, for branch circuits and 215.2(A), FPN No.2, for
conductors 8, 10, and 12 AWG shall be made of an AAfeeders.
8000 series electrical grade aluminum alloy conductor ma­ FPN No.2: For the allowable ampacities of Type MTW
terial. Stranded aluminum conductors 8 AWG through 1000 wire, see Table 13.5.1 in NFPA 79-2007, Electrical Stan­
dard for Industrial Machinery.
kcmil marked as Type RHH, RHW, XHHW, THW, THHW,
THWN, THHN, service-entrance Type SE Style U and SE (2) Selection of Ampacity. Where more than one calcu­
Style R shall be made of an AA-8000 series electrical grade lated or tabulated ampacity could apply for a given circuit
aluminum alloy conductor material.
length, the lowest value shall be used.
310.15 Ampacities for Conductors Rated 0-2000 Volts.
(A) General.
(1) Tables or Engineering Supervision. Ampacities for
conductors shall be permitted to be determined by tables as
provided in 310.15(B) or under engineering supervision, as
provided in 3l0.l5(C).
FPN No.1: Ampacities provided by this section do not
take voltage drop into consideration. See 210.19(A), FPN
Exception: Where two different ampacities apply to adjacent
portions of a circuit, the higher ampacity shall be
permitted to be used beyond the point of transition, a distance
equal to 3.0 m (10 ft) or 10 percent of the circuit
length figured at the higher ampacity, whichever is less.
FPN: See llO.14(C) for conductor temperature limitations
due to termination provisions.
(B) Tables. Ampacities for conductors rated 0 to 2000
volts shall be as specified in the Allowable Ampacity Table
2008 Edition NATIONAL ELECTRICAL CODE 70-145