Okay, I can help you with that. You are calculating box fill for a 384 cubic inch box, and are referencing Table 314.16(B) for the cubic inch volume allowances per conductor size.Here's a breakdown of how to proceed and what you need to consider

Understanding Box Fill Calculation - the Basics

The purpose of a box fill calculation is to ensure that the electrical box isn't overfilled, which could lead to: Overheating of conductors Damage to insulation Difficulty in making safe and proper connections Violations of electrical codes (NEC - National Electrical Code in the US)Steps for Box Fill Calculation1. Count the Conductors

Determine the

total number of conductors in the box. This includes: All current-carrying conductors

These are the wires actively carrying electricity (e.g., hot/ungrounded, neutral/grounded, and switch legs).

Grounding conductors

Count all equipment grounding conductors (EGCs) entering the box. You treat all grounding conductors as a single conductor based on the largest grounding conductor entering the box.

Conductors originating outside the box and terminating inside

Consider these.

Conductors that pass through the box without splice or termination

These conductors are counted only once.2.

Determine the Conductor Sizes

Note the size (AWG - American Wire Gauge) of

each conductor.3. Calculate Conductor Fill Volume

Using Table 314.16(B), find the cubic inch volume allowance for each conductor size. Multiply the number of conductors of each size by their respective cubic inch volume.
4.

Add Device Fill (if applicable)

If the box contains any devices (switches, receptacles, etc.), you need to add to the fill volume:

Device Fill

Each single gang device (switch, receptacle, etc.) counts as

two conductors based on the largest conductor connected to the device. This rule applies even if the device only has one terminal used.5. Add Equipment Grounding Conductor Fill (EGCs)

Regardless of the number of EGCs, you count them as one conductor based on the largest EGC entering the box.6.

Add Internal Cable Clamp Fill (if applicable)

If there are any internal cable clamps inside the box, count as one conductor based on the largest conductor entering the box. If the box is marked with its fill capacity with clamps present, that number is used.7.

Calculate Total Box Fill

Sum up the conductor fill volume (step 3), device fill (step 4), EGC fill (step 5), and internal cable clamp fill (step 6).8.

Compare to Box Volume

The total box fill (step 7) must not exceed the cubic inch volume of the box (384 cubic inches in your case).

Example Scenario (To Illustrate)

Let's say you have the following in your 384 cubic inch box: 10 x 12 AWG current carrying conductors 3 x 12 AWG grounding conductors 2 x Single gang devices with 12 AWG conductors. No internal cable clampsHere's the calculation:1. 12 AWG Conductors

10 conductors2.

Grounding Conductors

Count all the ground wires as one conductor based on the largest. Because they are all the same size, we count as a single 12AWG wire.3.

Device Fill

2 devices 2 conductors (per device) = 4 conductors

Total 12AWG

10 + 1 + 4 = 15 conductors.

Using Table 314.16(B)

12 AWG: 2.25 cubic inches per conductor Total volume = 15 conductors 2.25 cubic inches/conductor = 33.75 cubic inches

Check

Total box fill = 33.75 cubic inches Box volume = 384 cubic inches 33.75 cubic inches < 384 cubic inches

The box is NOT overfilled.Important Considerations



"Fittings" are not wires

Connectors (like wire nuts) do not affect box fill calculations.

Markings on boxes

Many boxes will be marked with their cubic inch volume. Use that number.

Non-metallic boxes

The fill requirements are the same for both metallic and non-metallic boxes.

How I can help you

To provide a more accurate calculation, please tell me:

The number of conductors of each size (AWG): (e.g., "5 x 12 AWG, 3 x 14 AWG, 2 x 10 AWG") The number of devices in the box (switches, receptacles, etc.) The size of the conductor connected to each device (AWG).* Are there internal cable clamps? If so, is the fill marked with the clamps present.Once you provide that information, I can do the calculation for you. Good luck! Flag for review