In a 4 in. × 4 in. × 1 1/2 in. box, what is the maximum number of 12 AWG THWN-2 conductors allowed?

To determine the maximum number of 12 AWG THWN-2 conductors allowed in a 4 in. × 4 in. × 1 1/2 in. box, it's essential to refer to the box fill requirements outlined in NEC Article 314.

The NEC specifies that for each conductor, you must allocate a specific volume in cubic inches. For 12 AWG conductors, each conductor requires 2.25 cubic inches of box fill space.

First, calculate the total volume of the box. A 4 in. × 4 in. × 1 1/2 in. box has a volume of 4 × 4 × 1.5 = 24 cubic inches.

Next, divide the total volume of the box by the cubic inch requirement per conductor:

24 cubic inches (total volume) ÷ 2.25 cubic inches (per conductor) = 10.67.

Since you cannot have a fraction of a conductor, you round down to the nearest whole number, which is 10 conductors.

However, when considering the fact that you also must account for additional fill space taken up by device fittings (like switches or receptacles) and equipment grounding conductors, it’s necessary