Correction and Adjustment Factors—See NEC Tables 310.15(B)(2)(a) and 310.15(B)(3)(a)

Correction Factors

Based on NEC Table 310.15(B)(2)(a) [formerly Table 310(16)] Ambient Temperature Correction Factors Based on 30°C (86°F).

Ambient Temperature
(°C)
Temperature Rating of Conductor Ambient Temperature
(°F)

60°C

75°C

90°C

10 or less 1.29 1.20 1.15

50 or less

11–15

1.22 1.15 1.12

51–59

16–20

1.15 1.11 1.08

60–68

21–25

1.08 1.05 1.04

69–77

26–30

1.00 1.00 1.00

78–86

31–35

0.91 0.94 0.96

87–95

36–40

0.82 0.88 0.91

96–104

41–45

0.71 0.82 0.87

105–113

46–50

0.58 0.75 0.82

114–122

51–55

0.41 0.67 0.76

123–131

56–60

0.58 0.71

132–140

61–65

0.47 0.65

141–149

66–70

0.33 0.58

150–158

71–75

0.50

159–167

76–80

0.41

168–176

81–85

0.29

177–185

Adjustment Factors

Where the number of current-carrying conductors in a raceway or cable exceeds three, the allowable ampacities shall be reduced as shown in the following table:

Number of Conductors * Percent of Values in Table 310.15(B)(16) through Table 310.15(B)(19) as Adjusted for Ambient Temperature if Necessary
4—6 80
7—9 70
10—20 50
21—30 45
31—40 40
41 and above 35

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