ARTICLE 310: Conductors for General Wiring

NEC Table 310.16

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Table 310.15(B)(2)(a) Adjustment Factors for Not More Than Three Current-Carrying Conductors in a Raceway or Cable

  Temperature Rating of Conductor  
Size AWG or kcmil 60°C
(140°F)
75°C
(167°F)
90°C
(194°F)
60°C
(140°F)
75°C
(167°F)
90°C
(194°F)
Size AWG or kcmil
Types TW, UF Types RHW, THHW, THW, THWN, XHHW, USE, ZW Types TBS, SA, SIS, FEP, FEPB, MI, RHH, RHW-2, THHN, THHW, THW-2, THWN-2, USE-2, XHH, XHHW, XHHW-2, ZW-2 Types TW, UF Types RHW, THHW, THW, THWN, XHHW, USE Types TBS, SA, SIS, THHN, THHW, THW-2, THWN-2, RHH, RHW-2, USE-2, XHH, XHHW, XHHW-2, ZW-2
COPPER ALUMINUM OR COPPER-CLAD ALUMINUM
18 14
16 18
14* 20 20 25
12* 25 25 30 20 20 25 12*
10* 30 35 40 25 30 35 10*
8 40 50 55 30 40 45 8
6 55 65 75 40 50 60 6
4 70 85 95 55 65 75 4
3 5 100 110 65 75 85 3
2 95 115 130 75 90 100 2
1 110 130 150 85 100 115 1
1/0 125 150 170 100 120 135 1/0
2/0 145 175 195 115 135 150 2/0
3/0 165 200 225 130 155 175 3/0
4/0 195 230 260 150 180 205 4/0
250 215 255 290 170 205 230 250
300 240 285 320 190 230 255 300
350 260 310 350 210 250 280 350
400 280 335 380 225 270 305 400
500 320 380 430 260 310 350 500
600 355 420 475 285 340 385 600
700 385 460 520 310 375 420 700
750 400 475 535 320 385 435 750
800 410 490 555 330 395 450 800
900 435 520 585 355 425 480 900
1000 455 545 615 375 445 500 1000
1250 495 590 665 405 485 545 1250
1500 520 625 705 435 520 585 1500
1750 545 650 735 455 545 615 1750
2000 560 665 750 470 560 630 2000
CORRECTION FACTORS
Ambient Temp. (°C) For ambient temperatures other than 30°C (86°F), multiply the allowable ampacities shown above by the appropriate factor shown below. Ambient Temp. (°F)
21-25 1.08 1.05 1.04 1.08 1.05 1.04 70-77
26-30 1.00 1.00 1.00 1.00 1.00 1.00 78-86
31-35 0.91 0.94 0.96 0.91 0.94 0.96 87-95
36-40 0.82 0.88 0.91 0.82 0.88 0.91 96-104
41-45 0.71 0.82 0.87 0.71 0.82 0.87 105-113
46-50 0.58 0.75 0.82 0.58 0.75 0.82 114-122
51-55 0.41 0.67 0.76 0.41 0.67 0.76 123-131
56-60 0.58 0.71 0.58 0.71 132-140
61-70 0.33 0.58 0.33 0.58 141-158
71-80 0.41 0.41 159-176

* Small Condutors. Unless specifically permitted in 240.4(E) through (G), the overcurrent protection shall not exceed 15 amperes for 14 AWG, 20 amperes for 12 AWG, and 30 amperes for 10 AWG copper; or 15 amperes for 12 AWG and 25 amperes for 10 AWG aluminum and copper-clad aluminum after any correction factors for ambient temperature and number of conductors have been applied.

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