Question 1

How do I determine the correct wire size?

Accepted Answer

Wire size is determined by load amperage, voltage drop over the run length, and termination temperature rating. Use NEC Table 310.16 for ampacity and apply correction/adjustment factors per 310.15. The wire must satisfy both ampacity and voltage drop requirements.

Question 2

What AWG wire is needed for 100 amps?

Accepted Answer

A 100-amp branch circuit typically requires 3 AWG copper or 1 AWG aluminum at 75°C terminations per NEC Table 310.16, before any derating. Service entrance conductors use 310.15(B)(7) reduced sizing.

Question 3

Do I need to upsize for voltage drop?

Accepted Answer

Yes. If the calculated voltage drop exceeds 3% on a branch circuit (recommended), the wire must be increased one or more sizes until the drop is within limits.

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