How many #10 conductors can be legally installed in a 4-inch square box that is 2-1/8 inches deep?

To determine how many #10 conductors can be legally installed in a 4-inch square box that is 2-1/8 inches deep, one must reference the National Electrical Code (NEC) guidelines related to conductor fill in electrical boxes.

The fill capacity of a box depends on its size and the type of conductors being used. For a 4-inch square box, the volume is typically calculated in cubic inches. The NEC states that each #10 conductor occupies a certain amount of space. Specifically, each #10 conductor counts as 2.0 cubic inches, and there are volume allowances for devices (like switches or receptacles) installed in the box as well.

For a box that is 2-1/8 inches deep, its volume can be calculated by first finding its cubic inches:

• The formula for a square box is: Volume = Length × Width × Depth.

• Here, the length and width are both 4 inches, and the depth is 2-1/8 inches (which is converted to 2.125 inches).

Calculating this gives:

Volume = 4 in × 4 in × 2.125 in = 33.0 cubic inches approximately.

According to NEC guidelines, when