Wire Ampacity
Sources |
NFPA 79 Industrial Machinery |
NFPA 70 National Electrical Code |
Temp Rating |
60 C |
75 C |
Inside Enclosure |
THHN 90 C |
THWN 75 C |
RUW 60 C |
28 | - | 0.8 | 0.8 | - | - | - |
26 | - | 1 | 1 | - | - | - |
24 | 2 | 2 | 2 | - | - | - |
22 | 3 | 3 | 3 | - | - | - |
20 | 5 | 5 | 5 | - | - | - |
18 | 7 | 7 | 7 | 14 | - | - |
16 | 10 | 10 | 10 | 18 | - | - |
14 | 15 | 15 | 20 | 25* | 20* | 20* |
12 | 20 | 20 | 25 | 30* | 25* | 25* |
10 | 30 | 30 | 40 | 40* | 30* | 30* |
8 | 40 | 50 | 60 | 55 | 50 | 40 |
6 | 55 | 65 | 80 | 75 | 65 | 55 |
4 | 70 | 85 | 105 | 95 | 85 | 70 |
2 | 95 | 115 | 140 | 130 | 115 | 95 |
*The load current an overcurrent protection shall not exceed 15amps for 14 AWG, 20 amps for 12 AWG, and 30 amps for 10 AWG copper. |
NEC 310 – Notes to Tables 310-16 through 310-318
Where the number of conductors in a raceway or cable exceed three, the ampacities given shall be reduced as shown in the following table. In addition, other derating factors (e.g., temperature) must be applied. |
Number of Conductors |
Percent of Values in Table (above) |
4 thru 6 | 80 |
7 thru 9 | 70 |
10 thru 24 * | 70 |
25 thru 42 * | 60 |
43 and above * | 50 |
* These factors include the effects of a load diversity of 50 percent. |
Flexible Cords and Cables
No. of Current Carrying Conductors |
Wire Size - AWG |
18 | 16 | 14 |
12 | 10 | 8 |
6 | 4 | 2 |
3 | 7 | 10 | 15 | 20 | 25 | 35 |
45 | 60 | 80 |
2 | 10 | 13 | 18 | 25 | 30 | 40 |
55 | 70 | 95 |
NEC 240-4
Flexible cord, including tinsel cord and extension cords, shall be protected against overcurrent in accordance with their ampacities as specified in Table 400-5.
Exception No.1: When a flexible cord or tinsel cord approved for and used with a listed appliance or portable lamp is connected to a branch circuit of Article 210 in accordance with the following:
- 20 ampere circuits, tinsel cord or No. 28 cord and larger.
- 30 ampere circuits, No. 16 cord and larger.
Exception No.3: Flexible cord used in tested extension cord sets having No. 16 AWG or larger conductors shall be considered to be protected by 20-ampere branch-circuit overcurrent protection.
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