How many No. 12 conductors can fit in a 4-11/16" box with a volume of 42 cubic inches?

• A. 10
• B. 12
• C. 18
• D. 20

Answer: (C)

To determine how many No. 12 conductors can fit in a 4-11/16" box with a volume of 42 cubic inches, it's important to refer to the NEC (National Electrical Code) guidelines for box fill calculations. For each No. 12 conductor, you typically allocate a specific volume allowance for the conductor itself and for any other devices or items that may be in the box, such as switches or receptacles.

Each No. 12 wire requires a volume of 2.25 cubic inches for adequate fill according to the code. To find out how many of these conductors will fit in the 42 cubic inch box, you would divide the total volume of the box by the volume required per conductor:

42 cubic inches (total box volume) ÷ 2.25 cubic inches (volume per No. 12 conductor) = 18 conductors.

This calculation accounts for the allowable fill, ensuring that the conductors can be safely and effectively accommodated within the box without risking overheating or other electrical safety issues. Therefore, knowing the volume allowance per conductor and applying it accurately to the total volume of the box leads to the conclusion that 18 No. 12 conductors can safely fit in a 4-