Electrical Code Calculations lvl 1 Lesson 5 - Performing Box Size and Fill Calculations

For an angle pull through the box shown, the minimum calculated length (A) of the box is ? , and the minimum calculated width (B) of the box is ? . All conductors are larger than 4 AWG and will not be spliced.

15 in. / 15 in.

The maximum number of 12 AWG THHN copper conductors that are permitted to be pulled directly through (without splice) in a standard 3/4-inch LB conduit body installed in a run of 3/4-inch RMC is ? .

16 Reference 314.16(C)

In general, two 12 AWG conductors pass unbroken through a lighting outlet box. Two 14 AWG conductors enter the box and splice to two 14 AWG conductors leaving the box and two 16 AWG fixture wires that supply a luminaire. Determine the minimum box volume required for this installation. Calculate the box volume to one decimal place.

16.0 in^3 Reference 314.16(B)

The minimum length and width of a pull box having an angle pull, with one three-inch conduit coming in and one three-inch conduit leaving, is ? . The conductors are larger than 4 AWG and will not be spliced.

18" Reference 314.28(A)(2)

Calculate the minimum depth required for a 411/16-inch square box that has four 3/C 10 AWG (plus ground) Type MC cables terminated within the box. Each 3/C 10 AWG Type MC cable has three 10 AWG circuit conductors plus one 10 AWG equipment grounding conductor (EGC) within the cable assembly.

2 1/8 in. deep

The minimum length (A) for the pull box shown is ? , provided that the conductors are larger than 4 AWG and will not be spliced.

24"

What is the minimum cubic inch (in.3) volume (or capacity) of each of the following metal boxes in accordance with Article 314? 3 in. × 2 in. × 21/2 in. device box 4 in. × 11/2 in. round box 4 in. × 21/8 in. octagonal box 4 in. × 21/8 in. square box

3 in. × 2 in. × 21/2 in. device box → 12.5 in.³ 4 in. × 11/2 in. round box → 15.5 in.³ 4 in. × 21/8 in. octagonal box → 21.5 in.³ 4 in. × 21/8 in. square box → 30.3 in.³

Two 12 AWG conductors pass through a switch box unbroken. Two 12 AWG conductors terminate on the switch (hot and switch leg) in the switch box. A bare 12 AWG equipment grounding conductor connects to the grounding screw in the box and continues through the box. Determine the minimum size metal device box suitable for this installation.

3 in. × 2 in. × 3 1/2 in. device box

An isolated equipment grounding receptacle is installed using a rigid nonmetallic conduit and a metal device box. Two 12 AWG conductors enter the box and are spliced to two 12 AWG conductors leaving the box and to two pigtails, which feed the receptacle. The 12 AWG isolated equipment ground has a pigtail splice for the receptacle and continues through the box. A bare 12 AWG equipment grounding conductor enters the box, connects to the box grounding screw, and continues on through the box. Determine the minimum size metal device box for this installation.

3 in. × 2 in. × 31/2 in. device box

What is the minimum length for a pull box when a four-inch run of RMC is installed for a straight pull provided that the conductors are sized 4 AWG and larger and are not spliced?

32 in Reference 314.28(A)(1)

What is the maximum number of 6 AWG THW copper conductors permitted in the installation shown below with the 11/4-inch LB conduit body and connected to the run of one-inch EMT?

4

Using both tables within Section 314.16, determine the minimum size standard metal square box needed for an installation in which two 12 AWG THHN copper conductors, two 14 AWG THHN copper conductors, and four 10 AWG THHN copper conductors are installed in the same box.

4 in. × 1 1/2 in.

Three conductors pass unbroken through a metal outlet box. In addition, one ungrounded conductor is spliced from a conductor leaving the box to a switch. A switch leg from the switch enters the box and is spliced to a fixture wire. A neutral is spliced to a fixture wire and carries on through the box. The two fixture wires (14 AWG) supply a luminaire. A fixture stud and a fixture hickey are installed in the box. All conductors are 12 AWG in metal raceways entering the metal box. There are no cable clamps contained within the box. Determine a minimum size metal outlet box suitable for this installation.

4 in. × 21/8 in. square box

Determine the total number of conductors in the junction box shown below when the luminaire is attached according to Article 314. Luminaire pigtail wires are 16 AWG TFF fixture wires.

6

According to the NEC, no conductor larger than ? is permitted to be installed in any standard metal box included in Table 314.16(A).

6 AWG

Determine the maximum number of conductors permitted for each of the following applications in accordance with Article 314. 6 AWG TW conductors in a 4 in. × 11/2 in. square box 12 AWG THHN conductors in a 411/16 in. × 11/2 in. square box 14 AWG TW conductors in a 3 in. × 2 in. × 11/2 in. device box 14 AWG THW conductors in a 4 in. × 11/2 in. octagonal metal box

6 AWG TW conductors in a 4 in. × 11/2 in. square box → 4 conductors 12 AWG THHN conductors in a 411/16 in. × 11/2 in. square box → 13 conductors 14 AWG TW conductors in a 3 in. × 2 in. × 11/2 in. device box → 3 conductors 14 AWG THW conductors in a 4 in. × 11/2 in. octagonal metal box → 7 conductors

Two 12 AWG conductors enter a box and are spliced to two 12 AWG conductors leaving the box with a pigtail feeding a duplex receptacle. A bare equipment grounding conductor is connected to the box, continues through the box, and is pigtailed to the grounding terminal of the receptacle. There are no internal cable clamps, fixture studs, or hickeys present in the box. What is the total count of conductors required to be used to determine the total box volume required for the installation?

7 - 12 AWG conductors

In accordance with Article 314, determine the volume allowance using the total number of conductors for the purposes of box fill in the device box as shown.

8

Using the following figure, calculate the number of conductors in the junction box in accordance with Article 314.

8

What is the smallest standard size metal box permitted for the following conductors in accordance with Article 314? Four 12 AWG RHH: ? octagonal box Six 10 AWG THW: ? device box Seven 6 AWG TW: ? square box Eight 12 AWG THHN: ? octagonal box

Four 12 AWG RHH: octagonal box → 4 in. × 1¼ in. Six 10 AWG THW: device box → 3 in. × 2 in. × 3½ in. Seven 6 AWG TW: square box → 4¹¹⁄₁₆ in. × 2⅛ in. Eight 12 AWG THHN: octagonal box → 4 in. × 2⅛ in.

The installation shown in the illustration consists of three 4/0 AWG copper conductors installed in a two-inch RMC passing through the pull box at right angles as shown. Determine if all three pull box dimensions of this installation are acceptable or a violation of the Code.

Violation