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)
Ambient Temperature (°C)	60°C	75°C	90°C	Ambient Temperature (°F)
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