Which option represents the correct box size for the described two-gang plaster ring when used with a 4 × 11/2 square box?

Which option represents the correct box size for the described two-gang plaster ring when used with a 4 × 11/2 square box?

• A. 4 × 21/8 square box with a 3.6 in3 two-gang plaster ring
• B. two - 3 × 2 × 2 device boxes (ganged to form a 2-gang box)
• C. 4 × 11/2 square box with a 5.0 in3 plaster ring
• D. two - 3 × 2 × 21/2 device boxes (ganged to form a 2-gang box)

Answer: (C)

Box fill calculations determine how much internal volume a box must have to safely contain all conductors, devices, and any internal clamps or rings. When you use a plaster ring, its own cubic-inch volume adds to the total fill, so the combination you choose must provide enough space for that ring plus the two devices and their wiring. The correct choice is the one that specifies a 4 × 11/2 square box with a plaster ring rated at 5.0 in^3. That ring volume, added to the box’s intrinsic capacity, meets the fill needed for a two-gang setup with two devices. The other options either use a different box size or a plaster ring with too little volume (or an arrangement that doesn’t pair properly with a plaster ring for a two-gang), which would not satisfy the box-fill requirements.

Box fill calculations determine how much internal volume a box must have to safely contain all conductors, devices, and any internal clamps or rings. When you use a plaster ring, its own cubic-inch volume adds to the total fill, so the combination you choose must provide enough space for that ring plus the two devices and their wiring.

The correct choice is the one that specifies a 4 × 11/2 square box with a plaster ring rated at 5.0 in^3. That ring volume, added to the box’s intrinsic capacity, meets the fill needed for a two-gang setup with two devices. The other options either use a different box size or a plaster ring with too little volume (or an arrangement that doesn’t pair properly with a plaster ring for a two-gang), which would not satisfy the box-fill requirements.