Question 1

What does ampacity mean?

Accepted Answer

Ampacity is the maximum continuous current a conductor can carry safely under specified installation conditions.

Question 2

Why are there different 60°C, 75°C, and 90°C ampacity values?

Accepted Answer

Different insulation temperature ratings allow different current levels. Always apply the most restrictive code and equipment termination limits.

Question 3

Does this table replace a full NEC design check?

Accepted Answer

No. It is a quick reference subset. Real designs must apply ambient correction, bundling adjustment, and local code requirements.

Question 4

Why does larger wire show lower AWG numbers?

Accepted Answer

AWG numbering is inverse: a smaller AWG number means a larger conductor and higher current capacity.

AWG	60°C (TW)	75°C (THW)	90°C (THHN)
10 AWG	30 A	35 A	40 A
8 AWG	40 A	50 A	55 A
6 AWG	55 A	65 A	75 A
4 AWG	70 A	85 A	95 A
3 AWG	85 A	100 A	115 A
2 AWG	95 A	115 A	130 A
1 AWG	110 A	130 A	150 A
1/0 AWG	125 A	150 A	170 A
2/0 AWG	145 A	175 A	195 A
3/0 AWG	165 A	200 A	225 A
4/0 AWG	195 A	230 A	260 A

AWG to Ampacity: 4/0 AWG

Value Details