What is the minimum size copper conductor that may be used for an overhead feeder which is 35 feet in length from a residence to a remote garage?

What is the minimum size copper conductor that may be used for an overhead feeder which is 35 feet in length from a residence to a remote garage?

• A. 8 AWG
• B. 6 AWG
• C. 10 AWG
• D. 4 AWG

Answer: (C)

The key idea is that for a feeder, size is driven by the current the feeder must carry (ampacity) and the voltage drop over the run, not distance alone. Over a short run like 35 feet, the voltage drop stays small enough for a modest load even with a smaller conductor, so you size primarily for the expected load with some allowance for voltage drop. Copper 10 AWG is typically good for about a 30 A load at residential temperatures, which is adequate for a small garage feeder with a modest continuous and noncontinuous load. The longer the run, the more voltage drop you’d have to watch for, but at 35 feet the drop remains within acceptable limits for common garage loads. The larger sizes shown (8, 6, or 4 AWG) would be more than is needed for that same modest load and would not be the minimum. If the actual feeder is intended to carry a much larger load (for example a 60 A or 100 A feeder), then you would choose the corresponding larger conductor (6 AWG for around 60 A, 4 AWG for higher amperage). But for this scenario, 10 AWG copper is the smallest size that meets typical small-garage feeder needs given the short run.

The key idea is that for a feeder, size is driven by the current the feeder must carry (ampacity) and the voltage drop over the run, not distance alone. Over a short run like 35 feet, the voltage drop stays small enough for a modest load even with a smaller conductor, so you size primarily for the expected load with some allowance for voltage drop.

Copper 10 AWG is typically good for about a 30 A load at residential temperatures, which is adequate for a small garage feeder with a modest continuous and noncontinuous load. The longer the run, the more voltage drop you’d have to watch for, but at 35 feet the drop remains within acceptable limits for common garage loads. The larger sizes shown (8, 6, or 4 AWG) would be more than is needed for that same modest load and would not be the minimum.

If the actual feeder is intended to carry a much larger load (for example a 60 A or 100 A feeder), then you would choose the corresponding larger conductor (6 AWG for around 60 A, 4 AWG for higher amperage). But for this scenario, 10 AWG copper is the smallest size that meets typical small-garage feeder needs given the short run.