Chapter 38 Wiring Methods
Section E3801 General Requirements
E3801.1 Scope.
This chapter covers the wiring methods for services, feeders and branch circuits for electrical power and distribution. (300.1)
E3801.2 Allowable wiring methods.
The allowable wiring methods for electrical installations shall be those listed in Table E3801.2. Single conductors shall be used only where part of one of the recognized wiring methods listed in Table E3801.2. As used in this code, abbreviations of the wiring-method types shall be as indicated in Table E3801.2. [110.8 and 300.3(A)]
ALLOWABLE WIRING METHOD | DESIGNATED ABBREVIATION |
Armored cable | AC |
Electrical metallic tubing | EMT |
Electrical nonmetallic tubing | ENT |
Flexible metal conduit | FMC |
Intermediate metal conduit | IMC |
Liquidtight flexible conduit | LFC |
Metal-clad cable | MC |
Nonmetallic sheathed cable | NM |
Rigid metallic conduit | RMC |
Rigid polyvinyl chloride conduit (Type PVC) | RNC |
Reinforced thermosetting resin conduit (Type RTRC) | RTRC |
Service entrance cable | SE |
Surface raceways | SR |
Underground feeder cable | UF |
Underground service cable | USE |
E3801.3 Circuit conductors.
All conductors of a circuit, including equipment grounding conductors and bonding conductors, shall be contained in the same raceway, conduit body, trench, cable or cord. [300.3(B)]
E3801.4 Wiring method applications.
Wiring methods shall be applied in accordance with Table E3801.4. (Chapter 3 and 300.2)
ALLOWABLE APPLICATIONS (application allowed where marked with an “A”) | AC | EMT | ENT | FMC | IMC | LFCa | MC | NM | SR | SE | UF | USE |
Services | — | A | Ah | Ai | A | Ai | A | — | — | A | — | A |
Feeders | A | A | A | A | A | A | A | A | — | Ac | A | Ab |
Branch circuits | A | A | A | A | A | A | A | A | A | Ac | A | — |
Inside a building | A | A | A | A | A | A | A | A | A | A | A | — |
Wet locations exposed to sunlight | — | A | Ah | — | A | A | Ak | — | — | A | Ae | Ae |
Damp locations | — | A | A | Ad | A | A | A | — | — | A | A | A |
Embedded in noncinder concrete in dry location | — | A | A | — | A | Aj | — | — | — | — | — | — |
In noncinder concrete in contact with grade | — | Af | A | — | Af | Aj | — | — | — | — | — | — |
Embedded in plaster not exposed to dampness | A | A | A | A | A | A | A | — | — | A | A | — |
Embedded in masonry | — | A | A | — | Af | A | A | — | — | — | — | — |
In masonry voids and cells exposed to dampness or below grade line | — | Af | A | Ad | Af | A | A | — | — | A | A | — |
Fished in masonry voids | A | — | — | A | — | A | A | A | — | A | A | — |
In masonry voids and cells not exposed to dampness | A | A | A | A | A | A | A | A | — | A | A | — |
Run exposed | A | A | A | A | A | A | A | A | A | A | A | — |
Run exposed and subject to physical damage | — | Al | — | — | Ag | — | — | — | — | — | — | — |
For direct burial | — | Af | — | — | Af | A | Ak | — | — | — | A | A |
For SI: 1 foot = 304.8 mm.
- a.
Liquidtight flexible nonmetallic conduit without integral reinforcement within the conduit wall shall not exceed 6 feet in length.
- b.
Type USE cable shall not be used inside buildings.
- c.
The grounded conductor shall be insulated.
- d.
Conductors shall be a type approved for damp or wet locations.
- e.
Shall be listed as “Sunlight Resistant.”
- f.
Metal raceways shall be protected from corrosion and approved for the application. Aluminum RMC requires approved supplementary corrosion protection.
- g.
RNC shall be Schedule 80. RTRC shall be RTRC-XW.
- h.
Shall be identified as “Sunlight Resistant” where exposed to the direct rays of the sun.
- i.
Conduit shall not exceed 6 feet in length.
- j.
Liquidtight flexible nonmetallic conduit is permitted to be encased in concrete where listed for direct burial and only straight connectors listed for use with LFNC are used.
- k.
In damp or wet locations where a corrosion-resistant jacket is provided over the metallic covering and any of the following conditions are met:
- 1.
The metallic covering is impervious to moisture.
- 2.
A jacket resistant to moisture is provided under the metal covering.
- 3.
The insulated conductors under the metallic covering are listed for use in wet locations.
- 1.
- l.
EMT shall not be subject to severe physical damage.
Section E3802 Above-Ground Installation Requirements
E3802.1 Installation and support requirements.
Wiring methods shall be installed and supported in accordance with Table E3802.1. (Chapter 3 and 300.11)
INSTALLATION REQUIREMENTS (Requirement applicable only to wiring methods marked “A”) | AC | EMT | ENT | FMC | NM | RNC | SE | SRa | USE |
Where run parallel with the framing member or furring strip, the wiring shall be not less than 1 1/4 inches from the edge of a furring strip or a framing member such as a joist, rafter or stud or shall be physically protected. | A | — | A | A | A | — | A | — | — |
Bored holes in framing members for wiring shall be located not less than 1 1/4 inches from the edge of the framing member or shall be protected with a minimum 0.0625-inch steel plate or sleeve, a listed steel plate or other physical protection. | Ak | — | Ak | Ak | Ak | — | Ak | — | — |
Where installed in grooves, to be covered by wallboard, siding, paneling, carpeting, or similar finish, wiring methods shall be protected by 0.0625-inch-thick steel plate, sleeve, or equivalent, a listed steel plate or by not less than 1 1/4-inch free space for the full length of the groove in which the cable or raceway is installed. | A | — | A | A | A | — | A | A | A |
Securely fastened bushings or grommets shall be provided to protect wiring run through openings in metal framing members. | — | — | Aj | — | A j | — | A j | — | — |
The maximum number of 90-degree bends shall not exceed four between junction boxes. | — | A | A | A | — | A | — | — | — |
Bushings shall be provided where entering a box, fitting or enclosure unless the box or fitting is designed to afford equivalent protection. | A | A | A | A | — | A | — | A | — |
Ends of raceways shall be reamed to remove rough edges. | — | A | A | A | — | A | — | A | — |
Maximum allowable on center support spacing for the wiring method in feet. | 4.5b, c | 10 | 3b | 4.5b | 4.5i | 3d | 2.5e, i | — | 2.5 |
Maximum support distance in inches from box or other terminations. | 12b, f, l | 36 | 36 | 12b, g | 12h, i | 36 | 12i | — | — |
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 degree = 0.0175 rad.
- a.
Installed in accordance with listing requirements.
- b.
Supports not required in accessible ceiling spaces between light fixtures where lengths do not exceed 6 feet.
- c.
Six feet for MC cable.
- d.
Five feet for trade sizes 1 1/4 through 2 inches, 6 feet for trade sizes 2 1/2 through 3, 7 feet for trade sizes 3 1/2 through 5 inches, 8 feet for trade size 6 inches.
- e.
Two and one-half feet where used for service or outdoor feeder and 4.5 feet where used for branch circuit or indoor feeder.
- f.
Twenty-four inches for Type AC cable and 36 inches for interlocking Type MC cable where flexibility is necessary.
- g.
Where flexibility after installation is necessary, lengths of flexible metal conduit and liquidtight flexible metal conduit measured from the last point where the raceway is securely fastened shall not exceed: 36 inches for trade sizes 1 /2 through 1 1/4, 48 inches for trade sizes 1 1/2 through 2, and 5 feet for trade sizes 2 1/2 and larger.
- h.
Within 8 inches of boxes without cable clamps.
- i.
Flat cables shall not be stapled on edge.
- j.
Bushings and grommets shall be listed, shall be installed prior to installation of cable and shall cover all metal edges.
- k.
- l.
Six feet for MC cable unless cable contains not more than four conductors sized not larger than 10 AWG.
E3802.2 Cables in accessible attics.
Cables in attics or roof spaces provided with access shall be installed as specified in Sections E3802.2.1 and E3802.2.2. (320.3 and 334.23)
E3802.2.1 Across framing members.
Where run across the top of framing members, or across the face of rafters or studding within 7 feet (2134 mm) of the floor or horizontal surface, in attics and roof spaces that are provided with access, the cable shall be protected by substantial guard strips that are at least as high as the cable. Where such spaces are not provided with access by permanent stairs or ladders, protection shall only be required within 6 feet (1829 mm) of the nearest edge of the attic entrance. [320.23(A) and 334.23]
E3802.2.2 Cable installed through or parallel to framing members.
Where cables are installed through or parallel to the sides of rafters, studs or floor joists, guard strips and running boards shall not be required, and the installation shall comply with Table E3802.1. [300.4(D), 320.23(B) and 334.23]
E3802.3 Exposed cable.
In exposed work, except as provided for in Sections E3802.2 and E3802.4, cable assemblies shall be installed as specified in Sections E3802.3.1 and E3802.3.2. (320.15, 330.15 and 334.15)
E3802.3.1 Surface installation.
Cables shall closely follow the surface of the building finish or running boards. [320.15 and 334.15(A)]
E3802.3.2 Protection from physical damage.
Where subject to physical damage, cables shall be protected by rigid metal conduit, intermediate metal conduit, electrical metallic tubing, Schedule 80 PVC conduit, RTRC-XW or other approved means. Where passing through a floor, the cable shall be enclosed in rigid metal conduit, intermediate metal conduit, electrical metallic tubing, Schedule 80 PVC conduit RTRC-XW or other approved means extending not less than 6 inches (152 mm) above the floor. Conduit or tubing shall be provided with a bushing or adapter that provides protection from abrasion at the point the cable enters and exits the raceway. [334.15(B)]
E3802.4 In unfinished basements and crawl spaces.
Where Type NM or SE cable is run at angles with joists in unfinished basements and crawl spaces, cable assemblies containing two or more conductors of sizes 6 AWG and larger and assemblies containing three or more conductors of sizes 8 AWG and larger shall not require additional protection where attached directly to the bottom of the joists. Smaller cables shall be run either through bored holes in joists or on running boards. Type NM or SE cable installed on the wall of an unfinished basement shall be permitted to be installed in a listed conduit or tubing or shall be protected in accordance with Table E3802.1. Conduit or tubing shall be provided with a bushing or adapter that provides protection from abrasion at the point where the cable enters and exits the raceway. The sheath of the Type NM or SE cable shall extend through the conduit or tubing and into the outlet, device or junction box not less than 1/4 inch (6.4 mm). The cable shall be secured within 12 inches (305 mm) of the point where the cable enters the conduit or tubing. Metal conduit, tubing, and metal outlet boxes shall be connected to an equipment grounding conductor complying with Section E3908.14. [334.15(C)]
E3802.5 Bends.
Bends shall be made so as not to damage the wiring method or reduce the internal diameter of raceways.
For Types NM, NMC and SE cable, bends shall be so made, and other handling shall be such that the cable will not be damaged and the radius of the curve of the inner edge of any bend shall be not less than five times the diameter of the cable. For flat cables, the major diameter dimension of the cable shall be used to determine the bending radius. (334.24 and 338.24)
3802.5.1 Cable entries.
The sheath on cables with nonmetallic sheaths shall extend not less than 1/4 inch (6 mm) beyond any cable clamp or cable entry. [334.19, 338.10(B)(4)(a)(1) and 340.10(4)]
E3802.6 Cable-securing means.
Cables shall be supported and secured by staples; cable ties listed and identified for securement and support; or straps, hangers or similar fittings designed and installed so as not to damage the cable. [320.30(A), 330.30(A), 334.30, 338.10(B)(4) and 340.10(4)]
E3802.7 Raceways exposed to different temperatures.
Where portions of a raceway or sleeve are known to be subjected to different temperatures and where condensation is known to be a problem, as in cold storage areas of buildings or where passing from the interior to the exterior of a building, the raceway or sleeve shall be sealed with an approved material to prevent the circulation of warm air to a colder section of the raceway or sleeve. Sealants shall be identified for use with the cable insulation, conductor insulation, a bare conductor, a shield or other components. [300.7(A)]
E3802.8 Raceways in wet locations above grade.
Where raceways are installed in wet locations above grade, the interior of such raceways shall be considered to be a wet location. Insulated conductors and cables installed in raceways in wet locations above grade shall be listed for use in wet locations. (300.9)
3802.9 Locations exposed to direct sunlight.
Insulated conductors and cables used where exposed to direct rays of the sun shall be listed as being “sunlight resistant” or shall be covered with insulating material, such as tape or sleeving, that is listed as being “sunlight resistant.” [310.10(D)]
Section E3803 Underground Installation Requirements
E3803.1 Minimum cover requirements.
Direct buried cable or raceways shall be installed in accordance with the minimum cover requirements of Table E3803.1. [300.5(A)]
LOCATION OF | TYPE OF WIRING METHOD OR CIRCUIT | ||||
1 | 2 | 3 | 4 | 5 | |
All locations not specified below | 24 | 6 | 18 | 12 | 6g, h |
In trench below 2-inch-thick concrete or equivalent | 18 | 6 | 12 | 6 | 6 |
Under a building | 0 | 0 | 0 | 0 | 0 |
Under minimum of 4-inch-thick concrete exterior slab with no vehicular traffic and the slab extending not less than 6 inches beyond the underground installation | 18 | 4 | 4 | 6 | 6 |
Under streets, highways, roads, alleys, driveways and parking lots | 24 | 24 | 24 | 24 | 24 |
One- and two-family dwelling driveways and outdoor parking areas, and used only for dwelling-related purposes | 18 | 18 | 18 | 12 | 18 |
In solid rock where covered by minimum of 2 inches concrete extending down to rock | 2 | 2 | 2 | 2 | 2 |
For SI: 1 inch = 25.4 mm.
- a.
Raceways approved for burial only where encased concrete shall require concrete envelope not less than 2 inches thick.
- b.
Lesser depths shall be permitted where cables and conductors rise for terminations or splices or where access is otherwise required.
- c.
Where one of the wiring method types listed in columns 1 to 3 is combined with one of the circuit types in columns 4 and 5, the shallower depth of burial shall be permitted.
- d.
Where solid rock prevents compliance with the cover depths specified in this table, the wiring shall be installed in metal or nonmetallic raceway permitted for direct burial. The raceways shall be covered by a minimum of 2 inches of concrete extending down to the rock.
- e.
Cover is defined as the shortest distance in inches (millimeters) measured between a point on the top surface of any direct-buried conductor, cable, conduit or other raceway and the top surface of finished grade, concrete, or similar cover.
- f.
EMT fittings used in direct burial applications shall be identified for direct burial.
- g.
A lesser depth shall be permitted where specified in the installation instructions of a listed low-voltage lighting system.
- h.
A depth of 6 inches shall be permitted for pool, spa, and fountain lighting that is installed in a nonmetallic raceway, limited to not more than 30 volts and part of a listed low-voltage lighting system.
E3803.2 Warning ribbon.
Underground service conductors that are not encased in concrete and that are buried 18 inches (457 mm) or more below grade shall have their location identified by a warning ribbon that is placed in the trench not less than 12 inches (305 mm) above the underground installation. [300.5(D)(3)]
E3803.3 Protection from damage.
Direct buried conductors and cables emerging from the ground shall be protected by enclosures or raceways extending from the minimum cover distance below grade required by Section E3803.1 to a point at least 8 feet (2438 mm) above finished grade. In no case shall the protection be required to exceed 18 inches (457 mm) below finished grade. Conductors entering a building shall be protected to the point of entrance. Where the enclosure or raceway is subject to physical damage, the conductors shall be installed in electrical metallic tubing, rigid metal conduit, intermediate metal conduit, Schedule 80 PVC conduit, RTRC-XW or the equivalent. [300.5(D)(1), (2) and (4)]
E3803.4 Splices and taps.
Direct buried conductors or cables shall be permitted to be spliced or tapped without the use of splice boxes. The splices or taps shall be made by approved methods with materials listed for the application. [300.5(E)]
E3803.5 Backfill.
Backfill containing large rock, paving materials, cinders, large or sharply angular substances, or corrosive material shall not be placed in an excavation where such materials cause damage to raceways, cables or other substructures or prevent adequate compaction of fill or contribute to corrosion of raceways, cables or other substructures. Where necessary to prevent physical damage to the raceway or cable, protection shall be provided in the form of granular or selected material, suitable boards, suitable sleeves or other approved means. [300.5(F)]
E3803.6 Raceway seals.
Conduits or raceways shall be sealed or plugged at either or both ends where moisture will enter and contact live parts. Spare or unused raceways shall also be sealed. Sealants shall be identified for the use with the cable insulation, conductor insulation, bare conductor or other components. [300.5(G)]
E3803.7 Bushing.
A bushing, or terminal fitting, with an integral bushed opening shall be installed on the end of a conduit or other raceway that terminates underground where the conductors or cables emerge as a direct burial wiring method. A seal incorporating the physical protection characteristics of a bushing shall be considered equivalent to a bushing. [300.5(H)]
E3803.8 Single conductors.
All conductors of the same circuit and, where present, the grounded conductor and all equipment grounding conductors shall be installed in the same raceway or shall be installed in close proximity in the same trench. [300.5(I)]
Exception: Conductors shall be permitted to be installed in parallel in raceways, multiconductor cables, and direct-buried single conductor cables. Each raceway or multiconductor cable shall contain all conductors of the same circuit, including equipment grounding conductors. Each direct-buried single conductor cable shall be located in close proximity in the trench to the other single conductor cables in the same parallel set of conductors in the circuit, including equipment grounding conductors. [300.5(I) Exception 1]
E3803.9 Earth movement.
Where direct buried conductors, raceways or cables are subject to movement by settlement or frost, direct buried conductors, raceways or cables shall be arranged to prevent damage to the enclosed conductors or to equipment connected to the raceways. [300.5(J)]
E3803.10 Wet locations.
The interior of enclosures or raceways installed underground shall be considered to be a wet location. Insulated conductors and cables installed in such enclosures or raceways in underground installations shall be listed for use in wet locations. [300.5(B)]
E3803.11 Under buildings.
Underground cable and conductors installed under a building shall be in a raceway. [300.5(C)]
Exception: Type MC Cable shall be permitted under a building without installation in a raceway where the cable is listed and identified for direct burial or concrete encasement and one or more of the following applies:
- 1.
The metallic covering is impervious to moisture.
- 2.
A moisture-impervious jacket is provided under the metal covering.
- 3.
The insulated conductors under the metallic covering are listed for use in wet locations. [300.5(C) Exception 2]