The shallowest 4 in by 2-1/8 in device box permitted for a setup with one hot, one neutral, and one EGC, with all conductors 14 AWG THHN/THWN, is which of the following?

The shallowest 4 in by 2-1/8 in device box permitted for a setup with one hot, one neutral, and one EGC, with all conductors 14 AWG THHN/THWN, is which of the following?

• A. 3 1/2 in deep masonry box
• B. 3 × 2 × 2-1/2 in switch box
• C. 3 × 2 × 3-1/2 in switch box
• D. 4 × 2-1/8 × 2-1/8 in handy box

Answer: (A)

When calculating box fill, you treat every conductor that originates outside the box and is terminated or spliced inside as one fill unit. Equipment grounding conductors count as 1/2 unit each, and the yoke (strap) of the device adds one fill unit. For a setup with two insulated conductors (hot and neutral), one equipment grounding conductor, and one device, the equivalents are: - hot: 1 unit - neutral: 1 unit - grounding conductor: 1/2 unit - device yoke: 1 unit Total: 3.5 fill units. With 14 AWG conductors, each fill unit equals 2.0 cubic inches, so the required box volume is 3.5 × 2.0 = 7.0 cubic inches. Among the given box options, the shallowest box that has enough internal volume to meet or exceed this 7 in³ requirement while fitting a 4 in by 2-1/8 in device-box footprint is the masonry box rated for 3-1/2 inches of depth. The other listed box types either do not provide sufficient usable volume in the same footprint or have design constraints (like clamps or internal accommodations) that reduce usable space below what’s needed for this particular fill calculation. Therefore, the shallowest permitted choice is the masonry box with 3-1/2 inch depth.

When calculating box fill, you treat every conductor that originates outside the box and is terminated or spliced inside as one fill unit. Equipment grounding conductors count as 1/2 unit each, and the yoke (strap) of the device adds one fill unit. For a setup with two insulated conductors (hot and neutral), one equipment grounding conductor, and one device, the equivalents are:

• hot: 1 unit

• neutral: 1 unit

• grounding conductor: 1/2 unit

• device yoke: 1 unit

Total: 3.5 fill units.

With 14 AWG conductors, each fill unit equals 2.0 cubic inches, so the required box volume is 3.5 × 2.0 = 7.0 cubic inches.

Among the given box options, the shallowest box that has enough internal volume to meet or exceed this 7 in³ requirement while fitting a 4 in by 2-1/8 in device-box footprint is the masonry box rated for 3-1/2 inches of depth. The other listed box types either do not provide sufficient usable volume in the same footprint or have design constraints (like clamps or internal accommodations) that reduce usable space below what’s needed for this particular fill calculation. Therefore, the shallowest permitted choice is the masonry box with 3-1/2 inch depth.