What is the minimum standard size square metal box required for two 12 AWG, two 14 AWG, and four 10 AWG THHN copper conductors?

To determine the minimum standard size square metal box required for accommodating the specified conductors, it's essential to consider the space necessary based on the wire gauge and the number of conductors. The National Electrical Code (NEC) outlines the cubic inch requirements for conductor fill.

Each of the conductors contributes a certain number of cubic inches to the box fill calculation. For THHN copper conductors, the dimensions for 12 AWG, 14 AWG, and 10 AWG need to be considered:

• Each 10 AWG THHN wire requires 1.34 cubic inches.

• Each 12 AWG THHN wire requires 0.98 cubic inches.

• Each 14 AWG THHN wire requires 0.64 cubic inches.

Applying this to the situation with two 12 AWG, two 14 AWG, and four 10 AWG wires:

• For the two 12 AWG wires: 2 x 0.98 = 1.96 cubic inches

• For the two 14 AWG wires: 2 x 0.64 = 1.28 cubic inches

• For the four 10 AWG wires: 4 x 1.34 = 5.36