If the service or feeder rating is 200 amps, what should the aluminum AWG size be?

For a service or feeder rating of 200 amps using aluminum conductors, the appropriate American Wire Gauge (AWG) size is 4/0. The size 4/0 aluminum wire is specifically designed to handle the current capacity required for a 200-amp service.

When selecting wire sizes, it is essential to consider the ampacity of the conductor material, which varies between copper and aluminum. Aluminum conductors require a larger size to carry the same amount of current as copper due to their lower conductivity. According to the National Electrical Code (NEC) and various electrical codes, a 4/0 aluminum wire is rated to safely conduct 200 amps under typical conditions.

The other sizes listed, including 12, 10, and 6 AWG, are insufficient to handle the current load effectively and could pose a risk of overheating and potentially causing a fire hazard if used for such a high ampacity application. Therefore, the appropriate size for a 200-amp service using aluminum is indeed 4/0.