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

The correct choice for the aluminum AWG size to use with a service or feeder rating of 200 amps is 4/0. This is based on the National Electrical Code (NEC) guidelines, which specify the appropriate wire sizes for different ampacities based on material type (copper or aluminum), insulation type, and installation conditions.

For aluminum conductors, a 4/0 AWG size is generally sufficient to safely handle 200 amps, ensuring that the conductor can carry the electrical load without exceeding its temperature rating, which would risk overheating and potential fire hazards.

Additionally, the sizing considers factors like the length of the run and the acceptable voltage drop; however, the 4/0 size is the standard for a 200 amp service in most residential and light commercial applications using aluminum wire. This choice ensures compliance with safety standards and optimal energy efficiency, making it a well-suited selection for the given amperage.