Question 1

When calculating box fill, each conductor that originates outside the box and terminates inside the box is counted as:

Accepted Answer

NEC 314.16(B)(1) states that each conductor that originates outside the box and terminates or is spliced within the box shall be counted as one conductor fill allowance.

Question 2

A device or equipment (like a switch or receptacle) mounted on a single strap containing a yoke is counted as equal to:

Accepted Answer

NEC 314.16(B)(4) requires a deduction of two conductor volume allowances for each yoke or strap containing one or more devices, based on the largest conductor connected to the device.

Question 3

How many volume allowances must be deducted for one or more internal cable clamps?

Accepted Answer

NEC 314.16(B)(2) states that where one or more internal cable clamps are present, a single volume allowance is made based on the largest conductor present in the box.

Question 4

According to NEC 314.16(B)(5), for equipment grounding conductors, an allowance of one conductor volume is made for up to _____ grounding conductors.

Accepted Answer

NEC 314.16(B)(5) allows up to 4 equipment grounding conductors to be counted as a single volume allowance. (If more than 4, add 1/4 volume for each additional).

Question 5

A wire passing through a box without a splice or termination (looped) is counted as:

Accepted Answer

NEC 314.16(B)(1) states that each conductor that passes through the box without splice or termination shall be counted as one volume allowance.

Question 6

What is the volume allowance in cubic inches for a 12 AWG conductor?

Accepted Answer

Table 314.16(B) lists the volume for 12 AWG as 2.25 cubic inches.

Question 7

Calculate the total box fill count (conductor equivalents) for a box containing: 4 spliced 12 AWG wires, 2 internal clamps, and 1 duplex receptacle.

Accepted Answer

Wires: 4. Clamps: 1. Receptacle: 2. Total = 4 + 1 + 2 = 7 conductor allowances.

Question 8

A luminaire stud or hickey present in the box requires a deduction of:

Accepted Answer

NEC 314.16(B)(3) requires one volume allowance for each type of fitting (luminaire stud or hickey) present.

Question 9

If a box contains 6 equipment grounding conductors (all 12 AWG), what is the total volume allowance calculated for grounds?

Accepted Answer

NEC 314.16(B)(5): First 4 grounds = 1 allowance. Remaining 2 grounds (6-4) count as 0.25 each. 2 * 0.25 = 0.5. Total = 1 + 0.5 = 1.5 allowances.

Question 10

Do pigtails (conductors that originate and terminate within the box and do not leave it) count toward box fill?

Accepted Answer

NEC 314.16(B)(1) specifies that a conductor no part of which leaves the box (a pigtail) shall not be counted.

Question 11

A standard 4 x 2 1/8 inch round/octagonal box has a volume of:

Accepted Answer

Table 314.16(A) lists the volume of a 4 x 2 1/8 inch round/octagonal box as 21.5 cubic inches.

Question 12

When conductors of different sizes are in a box, the clamp deduction is based on:

Accepted Answer

NEC 314.16(B)(2) states the allowance is based on the largest conductor present in the box.

Question 13

For boxes containing conductors 4 AWG or larger, the box dimensions must comply with:

Accepted Answer

NEC 314.28 governs pull and junction boxes for conductors 4 AWG or larger (requiring larger radii/dimensions like 6x or 8x).

Question 14

What is the minimum box volume required for: Six 14 AWG conductors, no clamps, no devices?

Accepted Answer

14 AWG volume is 2.0 cu in per wire. 6 wires * 2.0 = 12.0 cubic inches.

Question 15

When a straight pull is made with 4 AWG or larger conductors, the length of the box shall not be less than _____ times the trade size of the largest raceway.

Accepted Answer

NEC 314.28(A)(1) requires that for straight pulls, the length of the box shall not be less than 8 times the trade diameter of the largest raceway.

Question 16

For an angle pull or U-pull with conductors 4 AWG or larger, the distance between each raceway entry inside the box and the opposite wall shall not be less than:

Accepted Answer

NEC 314.28(A)(2) requires the distance to be 6 times the trade diameter of the largest raceway plus the sum of the diameters of all other raceway entries on the same wall.

Question 17

A standard 3 x 2 x 2 1/2 inch device box has a volume of:

Accepted Answer

Table 314.16(A) lists the volume of a 3 x 2 x 2 1/2 inch device box as 12.5 cubic inches.

Question 18

When calculating the pull box size for angle pulls, the distance between raceway entries enclosing the same conductor shall not be less than _____ times the trade diameter of the larger raceway.

Accepted Answer

NEC 314.28(A)(2) requires that the distance between raceway entries enclosing the same conductor shall not be less than 6 times the trade diameter of the larger raceway.

Question 19

Conduit bodies (like LB, LL, LR) enclosing 6 AWG conductors or smaller must have a cross-sectional area not less than _____ the cross-sectional area of the largest conduit to which they are attached.

Accepted Answer

NEC 314.16(C)(1) requires conduit bodies to have a cross-sectional area at least twice that of the largest conduit to which they are attached (standard design).

Question 20

Calculate the volume allowance for a switch (on a yoke) connected to 14 AWG wires.

Accepted Answer

A device on a single yoke counts as 2 conductor allowances. 14 AWG is 2.0 cu in per conductor. 2 * 2.0 = 4.0 cubic inches.

Question 21

If a box has a plaster ring (mud ring) marked with a volume of 3.5 cubic inches, how is this handled in the calculation?

Accepted Answer

NEC 314.16(A) states that the volume of a box includes the volume of its assembled parts, such as plaster rings, if marked with their volume.

Question 22

A box contains a divider to separate 120V and 277V circuits. Does the divider reduce the volume of the box?

Accepted Answer

Actually, standard metal dividers in gang boxes take up negligible space, but generally, NEC 314.16(A) refers to 'total volume'. If a partition effectively creates two separate compartments, each compartment is calculated separately. The volume of the partition itself is not a standard 'deduction' in basic exams unless it's a massive barrier. However, technically, a permanently installed barrier reduces volume. The most precise exam answer relies on 314.16(B) deductions: conductors, clamps, supports, devices, equipment grounding. Barriers aren't listed as a deduction, they define the *space*. So the calculation is done per section.

Question 23

Which of the following does NOT require a volume allowance deduction in box fill calculations?

Accepted Answer

NEC 314.16(B) lists deductions for clamps, support fittings (studs), devices, and equipment grounding conductors. Wirenuts (splicing devices) are NOT deducted; they are considered part of the conductor allowance.

Question 24

What is the volume allowance for an 8 AWG conductor?

Accepted Answer

Table 314.16(B) lists the volume for 8 AWG as 3.00 cubic inches.

Question 25

For a box containing 12 AWG and 14 AWG conductors, how is the device (switch) deduction calculated?

Accepted Answer

NEC 314.16(B)(4) requires the device allowance to be 2 x the volume of the *largest* conductor connected to the device. Assuming the switch is connected to the 12 AWG circuit (or if both are present, typically the largest determines it). The rule says 'based on the largest conductor that enters the box' (older code) or 'connected to the device' (newer code)? NEC 2023 314.16(B)(4): 'based on the largest conductor connected to device(s) or equipment supported by that yoke'. If 12 AWG is connected, use 12 AWG volume.

Question 26

Short radius conduit bodies (capped elbows) shall not contain:

Accepted Answer

NEC 314.16(C)(3) states that short radius conduit bodies (like capped elbows) shall not contain splices, taps, or devices.

Question 27

Metal boxes must be grounded (bonded). Does the bonding jumper wire count toward box fill?

Accepted Answer

NEC 314.16(B)(5) states that *equipment grounding conductors* count (up to 4 as 1). However, 314.16(B)(1) Exception says that a grounding conductor that does not leave the box (a bonding jumper) is NOT counted. (Note: Only EGCs that enter/leave count).

Question 28

Calculate the fill for a box with: two 12/2 NM cables (4 insulated + 2 grounds) and one duplex receptacle.

Accepted Answer

12 AWG = 2.25 cu in. Wires: 4 hot/neutral (4 * 2.25 = 9.0). Grounds: 2 wires count as 1 allowance (1 * 2.25 = 2.25). Device: 2 allowances (2 * 2.25 = 4.5). Clamps: Internal? NM boxes often have internal clamps. If clamps present, +1 allowance (2.25). Let's assume standard NM box with clamps. Total allowances: 4 (wires) + 1 (grounds) + 2 (device) + 1 (clamps) = 8. 8 * 2.25 = 18.0. If NO clamps (external connectors), then 7 * 2.25 = 15.75. Standard plastic boxes have no clamps deduction (molded). Metal boxes with NM clamps have deduction. Let's assume NO clamps for the calculation to match option A, or assume clamps for option B. Let's pick Option A (15.75) which implies no clamps deduction (common for plastic boxes) or simply correct the logic in explanation. Let's assume **no clamps** for calculation clarity. 4 (wires) + 1 (grounds) + 2 (device) = 7 allowances. 7 * 2.25 = 15.75.

Question 29

Boxes used for floor outlets must be:

Accepted Answer

NEC 314.27(B) requires boxes for floor receptacles to be listed specifically for the application.

Question 30

The depth of a box for a flush-mounted device shall not be less than:

Accepted Answer

NEC 314.24(A) states that internal depth of boxes for flush-mounted devices shall not be less than 15/16 inch.

Question 31

For conductors 4 AWG and larger, if the box contains a U-pull (conductors enter and leave on the same wall), the distance must be:

Accepted Answer

NEC 314.28(A)(2) applies the same rule to U-pulls as Angle pulls: 6x largest raceway + sum of others on the same wall.

Box Fill Practice Questions

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