Technical data

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183
XT IEC Power Control
June 2005
Reference Data
Ampacities of Insulated Conductors (Based on 1996 NEC

) — Continued
Table 310-18. Allowable Ampacities of Three Single Insulated Conductors Rated 0 – 2000V,
150° – 250°C (302° – 482°F), in Raceway or Cable Based on Ambient Air Temperature of
40°C (104°F)

Reprinted by permission from NFPA 70-1996. National Electrical Code
®
, Copyright
©
1996.
National Fire Protection Association, Batterymarch Park, Quincy, MA 02269.
Notes to Tables 310-16, 310-18 — Continued
8. Adjustment Factors. (continued)
Exception No. 1
Where conductors of different sys-
tems, as provided in Section 300-3,
are installed on a common raceway
or cable, the derating factors shown
shall apply to the number of power
and lighting (Articles 210, 215, 220
and 230) conductors only.
Exception No. 2
For conductors installed in cable trays,
the provisions of Section 318-11 shall
apply.
Exception No. 3
Derating factors shall not apply to con-
ductors in nipples having a length not
exceeding 24 in. (610 mm).
Size Temperature Rating of Conductor. See NEC Table 310-13. Size
AWG
kcmil
150°C
(302°F)
200°C
(392°F)
250°C
(482°F)
150°C
(302°F)
AWG
kcmil
Type
Z
Types
FEP, FEPB, PFA
Types
PFAH, TFE
Type
Z
Copper Nickel or
Nickel-Coated
Copper
Aluminum or
Copper-Clad
Aluminum
14
12
10
8
34
43
55
76
36
45
60
83
39
54
73
93
—
30
44
57
14
12
10
8
6
4
3
2
1
96
120
143
160
186
110
125
152
171
197
117
148
166
191
215
75
94
109
124
145
6
4
3
2
1
1/0
2/0
3/0
4/0
215
251
288
332
229
260
297
346
244
273
308
361
169
198
227
260
1/0
2/0
3/0
4/0
250
300
350
400
500
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
250
300
350
400
500
600
700
750
800
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
600
700
750
800
1000
1500
2000
—
—
—
—
—
—
—
—
—
—
—
—
1000
1500
2000
Correction Factors
Ambient
Temp. °C
For Ambient Temperatures Other Than 40°C (104°F), Multiply the
Allowable Ampacities Shown Above By the Appropriate Factor
Shown Below
Ambient
Temp. °F
41 – 50
51 – 60
61 – 70
71 – 80
81 – 90
91 – 100
101 – 120
121 – 140
141 – 160
161 – 180
181 – 200
201 – 225
.95
.90
.85
.80
.74
.67
.52
.30
—
—
—
—
.97
.94
.90
.87
.83
.79
.71
.61
.50
.35
—
—
.98
.95
.93
.90
.87
.85
.79
.72
.65
.58
.49
.35
.95
.90
.85
.80
.74
.67
.52
.30
—
—
—
—
105 – 122
123 – 140
141 – 158
159 – 176
177 – 194
195 – 212
213 – 248
249 – 284
285 – 320
321 – 356
357 – 392
393 – 437
Exception No. 4
Derating factors shall not apply to
underground conductors entering or
leaving an outdoor trench if those con-
ductors have physical protection in the
form of rigid metal conduit, intermedi-
ate metal conduit, or rigid nonmetallic
conduit having a length not exceeding
10 ft. (3.05m) and the number of con-
ductors does not exceed four.
Exception No. 5.
For other loading conditions, adjust-
ment factors and ampacities shall be
permitted to be calculated under
Section 310-15(b).
(FPN): See Appendix B, Table B-310-11,
for adjustment factors for more than
three current-carrying conductors in a
raceway or cable with load diversity.
(b) More Than One Conduit, Tube
or Raceway. Spacing between con-
duits, tubing or raceways shall be
maintained.
9. Overcurrent Protection. Where
the standard ratings and settings of
overcurrent devices do not correspond
with the ratings and settings allowed
for conductors, the next higher
standard rating and setting shall be
permitted.
Exception: As limited in Section 240-3.
10. Neutral Conductor.
(a) A neutral conductor that carries
only the unbalanced current from
other conductors of the same circuit
need not be counted when applying
the provisions of Note 8.
(b) In a 3-wire circuit consisting of two
phase wires and the neutral of a 4-wire,
3-phase wye-connected system, a com-
mon conductor carries approximately
the same current as the line-to-neutral
load currents of the other conductors
and shall be counted when applying
the provisions of Note 8.
(c) On a 4-wire, 3-phase wye circuit
where the major portion of the load
consists of nonlinear loads, there are
harmonic currents present in the neu-
tral conductor, and the neutral shall be
considered to be a current-carrying
conductor.
11. Grounding or Bonding Conductor.
A grounding or bonding conductor
shall not be counted when applying
the provisions of Note 8.