Article 314 Outlet, Device, Pull, and Junction Boxes; Conduit Bodies; Fittings; and Handhole Enclosures

I. Scope and General

314.1

Scope

Refer to this section in the NEC® for inclusions and exclusions.

314.2

Round Boxes

These are not permitted if locknuts or bushings are required on the side of the box.

314.3

Nonmetallic Boxes

These are only to be used with nonmetallic sheathed cable or raceways, flexible cords, open wire on insulator installations, or knob-and-tube concealed wiring. They can be used with metal raceway or metal-jacketed cable only if there is a means for integral bonding or internal bonding. There are two exceptions.

314.4

Metal Boxes

These must be grounded.

314.5

Short Radius Conduit Bodies

Conduit bodies, like capped elbows, which enclose 6 AWG or smaller conductors and are used only to allow the installation of the raceway and its conductors can not have splices, taps, or devices and they must be large enough for free space for the conductors.

II. Installation

314.15

Damp, Wet Locations or Hazardous (Classified) Locations

Moisture must be prevented from getting into the box. They must be listed for use in wet locations. When installed in a hazardous location, conform to Articles 500 through 517.

314.16

Number of Conductors in Outlet, Device and Junction Boxes, and Conduit Bodies

The reader is referred to this section for complete information. These items must be large enough to allow free space for all the enclosed conductors. The volume of the box as calculated in this section cannot be smaller than the fill calculation. This does not apply to terminal housings supplied with the motors (refer to Section 430.12). For enclosed conductors 4 AWG or larger, the provisions of Section 314.28 must be complied with.

(A) Box Volume Calculations. The volume is the total of the assembled sections and if used, spaces from plaster rings, domed covers, extension rings, and the like that are made from boxes listed in Table 314.16(A) or have the volume marked.

Table 314.16(A). Metal Boxes

Box Trade Size

Minimum Volume

Maximum Number of Conductors[*]

mm

in.

 

cm3

in.3

18

16

14

12

10

8

6

100 x 32

(4 x 1¼)

round/octagonal

205

12.5

8

7

6

5

5

5

2

100 x 38

(4 x 1½)

round/octagonal

254

15.5

10

8

7

6

6

5

3

100 x 54

(4 x 21/8)

round/octagonal

353

21.5

14

12

10

9

8

7

4

100 x 32

(4 x 1¼)

square

395

18.0

12

10

9

8

7

6

3

100 x 38

(4 x 1½)

square

344

21.0

14

12

10

9

8

7

4

100 x 54

(4 x 21/8)

square

497

30.3

20

17

15

13

12

10

6

120 x 32

(4 x ¼)

square

418

25.5

17

14

12

11

10

8

5

120 x 38

(4 x 1½)

square

484

29.5

19

16

14

13

11

9

5

120 x 54

(4 x 21/8)

square

689

42.0

28

24

21

18

16

14

8

75 x 50 x 38

(3 x 2 x 1½)

device

123

7.5

5

4

3

3

3

2

1

75 x 50 x 50

(3 x 2 x 2)

device

164

10.0

6

5

5

4

4

3

2

75 x 50 x 57

(3 x 2 x 2¼)

device

172

10.5

7

6

5

4

4

3

2

75 x 50 x 65

(3 x 2 x 2½)

device

205

12.5

8

7

6

5

5

4

2

75 x 50 x 70

(3 x 2 x 2¾)

device

230

14.0

9

8

7

6

5

4

2

75 x 50 x 90

(3 x 2 x 3½)

device

295

18.0

12

10

9

8

7

6

3

100 x 54 x 38

(4 x 21/8 x 1½)

device

169

10.3

6

5

5

4

4

3

2

100 x 54 x 48

(4 x 21/8 x 17/8)

device

213

13.0

8

7

6

5

5

4

2

100 x 54 x 54

(4 x 21/8 x 21/8)

device

238

14.5

9

8

7

6

5

4

2

95 x 50 x 65

(3¾ x 2 x 2½)

masonrybox/gang

230

14.0

9

8

7

6

5

4

2

95 x 50 x 90

(3¾ x 2 x 3½)

masonry box/gang

344

21.0

14

12

10

9

8

7

2

min. 44.5 depth

FSsingle cover/gang (1¾)

221

13.5

9

7

6

6

5

4

2

min. 60.3 depth

FDsingle cover/gang (23/8)

295

18.0

12

10

9

8

7

6

3

min. 44.5 depth

FSmultiple cover/gang (1¾)

295

18.0

12

10

9

8

7

6

3

min. 60.3 depth

FDmultiple cover/gang (23/8)

395

24.0

16

13

12

10

9

8

4

[*] Where no volume allowances are required by 314.16(B)(2) through 314.16(B)(5).

(1) Standard Boxes. Given in Table 314.16(A).

(2) Other Boxes. If the box is 100 cubic inches or less [except those in Table 314.16(A)] and nonmetallic boxes must have the capacity marked by the manufacturer. If the box is listed in Table 314.16(A) and has a larger capacity, the manufacturer can mark it.

(B) Box Fill Calculations.

(1) Conductor Fill. Every conductor that originates outside the box and terminates or is spliced in the box and each conductor passing through the box is counted once. A conductor that is looped and unbroken which is not less than twice the minimum length for a free conductor as referred to in 300.14 is counted twice. The fill is computed using Table 314.16(B). If a conductor has no part leaving the box, it is not counted. There is an exception for equipment grounding conductors.

(2) Clamp Fill. If an internal clamp is used there, a single volume allowance in accordance with Table 314.16(B) is made based on the largest conductor in the box.

(3) Support Fittings Fill. If a stud or hickey is there, a single volume allowance in accordance with Table 314.16(B) is made based on the largest conductor in the box.

(4) Device or Equipment Fill. For a strap or yoke containing a device or equipment, a double volume allowance is made in accordance with Table 314.16(B) based on the largest conductor connected to the device or equipment.

(5) Equipment Grounding Fill. If equipment grounding conductors come into the box, a single volume allowance is made in accordance with Table 314.16(B) and is based on the largest equipment grounding conductor present. If additional equipment grounding conductors as noted in 250.146(D), come into the box an additional volume allowance is made based on the largest equipment grounding conductor in this set.

Table 314.16(B). Volume Allowance Required per Conductor

 

Free Space within Box for Each Conductor

Size of Conductor (AWG)

cm3

m3

18

24.6

1.50

16

28.7

1.75

14

32.8

2.00

12

36.9

2.25

10

41.0

2.50

8

49.2

3.00

6

81.9

5.00

(c) Conduit Bodies. Generally conduit bodies enclosing 6 AWG conductors or smaller must have cross-sectional area not less than twice the area of the largest conduit or tubing attached. The maximum number of conductors is shown in Table 1, Chapter 9. There are additional requirements noted in the Code.

314.17

Conductors Entering Boxes, Conduit Bodies, or Fittings

All openings must be closed. All conductors coming into a box, conduit body, or fitting must be protected against abrasion. Special requirements are indicated with open wiring or concealed knob-and-tube wiring. If cable or raceway is used, the cable or raceway must be fastened to the box, conduit body, or fitting. Refer to Section 300.15(C) of the NEC® for an exception and to Section 300.4(F) for wire 4 AWG or larger. The reader is referred to this section for complete details.

314.19

Boxes Enclosing Flush Devices

They must be closed on the back and sides and a support for the device (usually a stud or screw hole) must be in the box. The screw that supports the box cannot be used to attach the device.

314.20

In Wall or Ceiling

When the box is set in concrete, tile, or other noncombustible material, it can be set back as much as 6 mm (¼ in.) When it is set in combustible material, it has to be flush with the finished surface.

314.21

Repairing Plaster and Drywall or Plasterboard

314.22

Exposed Surface Extensions

314.23

Supports

This section details methods of support. It indicates where they are needed and what can be used.

314.24

Depth of Outlet Boxes

314.25

Covers and Canopies

314.27

Outlet Boxes

They must be designed for the purpose to be used (i.e., floor or lighting fixture). A fixture support must be in a lighting fixture box. Cannot be used as sole support for ceiling paddle fans unless listed for that purpose. There are special cases. The reader is referred to this section in the NEC®.

314.28

Pull and Junction Boxes and Conduit Bodies

(A) Minimum Size. The following rules apply only when the wire is 4 AWG or larger. In a straight pull, the box must be at least 8 times the metric/designator (trade size) of the largest raceway in length. When angle pulls or U-pulls are used, the distance between the raceway entrances and the opposite wall must be at least 6 times the metric designator (trade size) of the largest raceway in a row. In addition, that distance must be increased by the diameter of each additional raceway in any one row on the same wall of the box. Since each row is calculated individually, the largest distance for a single row is used. Two raceways that enclose the same conductor cannot be closer than 6 times the metric designator (trade size) of the larger raceway. There is an exception where the entry is opposite a removable cover. There is also a provision for boxes or conduit bodies whose dimensions are less than calculated where combination of conductors are used.

(B) Conductors in Pull or Junction Boxes

(C) Covers

(D) Permanent Barriers. If a permanent barrier is in a box, each section is considered a box.

314.29

Boxes and Conduit Bodies to Be Accessible

314.30

Handhole Enclosures

They must be designed and installed to withstand any load that might be imposed.

(A) Size. For conductors operating at 600 volts or lower, they must be sized as stated in 314.28(A). For conductors operating above 600 volts they must be sized as stated in 314.71. There is a provision for handholes without bottoms.

(B) Wiring Entries. If underground raceways and cable assemblies enter a handhole they must extend into the enclosure but are not required to be mechanically connected to the enclosure.

(C) Handhole Enclosures Without Bottoms. All enclosed conductors, splices, or terminations must be listed for wet locations if installed in a handhole without a bottom.

(D) Covers. They have to have an identifying mark or logo that tells the function of the handhole. The example given in the Code is "electric." They must weigh over 45 kg (100 lb.) or require the use of tools to open. Any metal cover and any exposed conductive surface has to be bonded in accordance with 250.96(A).

III. Construction Specifications

314.40

Metal Boxes, Conduit Bodies, and Fittings

314.41

Covers

314.42

Bushings

314.43

Nonmetallic Boxes

314.44

Marking

 

IV. Pull and Junction Boxes for Use on Systems Over 600 Volts, Nominal

314.70

General

314.71

Size of Pull and Junction Boxes

314.72

Construction and Installation Requirements


Article 90 Introduction

General

Wiring and Protection

Wiring Methods and Materials

Equipment for General Use

Special Occupancies

Special Equipment

Special Conditions

Tables

Annex C. Conduit and Tubing Fill Tables for Conductors and Fixture Wires of the Same Size

Annex D. Examples

Annex E. Types of Construction

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Pocket Guide to the National Electrical Code 2005
Pocket Guide to the National Electrical Code(R), 2005 Edition (8th Edition)
ISBN: 0131480014
EAN: 2147483647
Year: 2004
Pages: 120
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