This is not an official copy of the Philippine Electrical Code. This is a Design Guide according to the provisions of the Philippine Electrical Code. It also provides interpretation and annotations of the clauses of the Philippine Electrical Code. Any information, interpretation and/or annotation presented herein are based on personal opinion of the authors and does not represent the official interpretation of the Philippine Electrical Code.
You’re reading an outdated article. Please go to the recent issues to find up-to-date content. Article 314 of the National Electrical Code covers the installation and use of all boxes and conduit bodies used as outlet, device, junction or pull boxes, depending on their use. As indicated by the title, this article covers more than just boxes, it also includes manholes and other electric enclosures intended for personnel entry. Article 314 also includes installation requirements for fittings used to join raceways and to connect raceways and cables to boxes and conduit bodies. Fittings used to join raceways include, but are not limited to, couplings. Likewise, fittings used to connect raceways and cables to boxes and conduit bodies include, but are not limited to, connectors (See Figure 1). The middle sentence in 314.1 clarifies that cast, sheet metal, nonmetallic and other boxes such as FS, FD and larger boxes are not classified as conduit bodies. A conduit body, as defined in Article 100, is a separate portion of a conduit or tubing system that provides access through a removable cover(s) to the interior of the system at a junction of two or more sections of the system or at a terminal point of the system. Article 314 is divided into five parts: I. Scope and General; II. Installation; III. Construction Specifications; IV. Manholes and Other Electric Enclosures Intended for Personnel Entry; and V. Pull and Junction Boxes for Use on Systems Over 600 Volts, Nominal. Specifications for box fill calculations are in the section titled Installation (Part II). 314.15 Damp, Wet or Hazardous Locations Boxes, conduit bodies and fittings in damp or wet locations, must be placed or equipped so as to prevent moisture from entering or accumulating within the box [314.15(A)]. Damp locations, as defined in Article 100, are locations protected from weather and are not subject to saturation with water or other liquids. Locations subject to moderate degrees of moisture are classified as damp locations. Partially protected external locations under canopies, marquees, roofed open porches and similar sites are considered damp locations. Interior locations such as certain basements, barns and cold-storage warehouses are also classified as damp locations. Dry locations are not normally subject to dampness or wetness, except on a temporary basis, such as a building under construction. Boxes, conduit bodies, and fittings installed in wet locations must be listed for that specific use [314.15(A)]. Installations in any of the following categories are wet locations: underground, within concrete slabs, in masonry (directly contacting the earth), areas subject to saturation with water or other liquids (such as vehicle washing areas), and locations unprotected from weather [Article 100]. Weatherproof, also defined in Article 100, is constructed or protected so that exposure to the weather will not interfere with successful operation. The fine print note (FPN) under the definition for weatherproof states that rainproof, raintight or watertight equipment can fulfill the requirements for weatherproof where varying weather conditions other than wetness, such as snow, ice, dust or temperature extremes, are not a factor. Two fine print notes are under 314.15(A). The first FPN refers the reader to 314.27(C) for boxes in floors, and the second references 300.6 for protection against corrosion. Hazardous (classified) location installations must comply with Articles 500 through 517 [314.15(B)]. 314.16 Number of Conductors in Outlet, Device and Junction Boxes, and Conduit Bodies Boxes and conduit bodies must be of sufficient size to provide free space for all enclosed conductors (See Figure 2). The term “free space” should not be confused with “free conductor” located in 300.14. Contrary to the opinion of some electricians, there are requirements that limit the number of conductors allowed within outlet, device, pull and junction boxes. Many times, when covers are removed from junction boxes, it is discovered that the box is packed full of conductors, and no consideration was given to the sizes and numbers of conductors. Disregarding box fill requirements can create safety as well as fire hazards (See Figure 3). Article 314 contains detailed requirements for box fill and junction box sizing. Two sections refer to box fill calculations: 314.16(A) Box Volume Calculations, and 314.16(B) Box Fill Calculations. In no case shall the volume of the box, as calculated in 314.16(A), be less than the fill calculation as determined in 314.16(B). Requirements for calculating the minimum volume for conduit bodies are located in 314.16(C). Conduit bodies, also referred to as condulets, are manufactured with a variety of configurations. The Type (i.e., LB, LR, LL, C, T, etc.) indicates the number and location of conduit entries. Unlike junction boxes and conduit bodies, terminal housings supplied with motors are not required to meet box fill requirements. Use 314.16 to determine the size box required for conductors 18 AWG through 6 AWG. These boxes are calculated by using the number of conductors and their respective sizes. Boxes and conduit bodies enclosing conductors 4 AWG or larger must also comply with the provisions of 314.28. 314.16(A) Box Volume Calculations Various sizes of metal boxes are listed in Table 314.16(A). The table’s first section contains the box trade size in millimeters, and inches, as well as a description of the box. The middle section gives the minimum volume in cubic millimeters and cubic inches. The last section provides the maximum number of 18 through 6 AWG conductors permitted in each of the boxes. The maximum number of conductors is based on the same size conductors in the box. For example, what is the maximum number of 12 AWG conductors permitted in a 4-inch-square box with a depth of 11/2 inches? There will be no fittings or devices in the box. First, look at the left side of Table 314.16(A) and find the row with a 4-inch-square box having a depth of 11/2 inches. Next, follow the row across to the column under 12. The maximum number of 12 AWG conductors permitted in a 4-inch-square box with a depth of 11/2 inches is nine (See Figure 4). This means a total of nine conductors, not nine conductors from each conduit entering the box. This also means the box cannot contain any fittings or devices (See Figure 5). Slang words and phrases are used in every trade, and the electrical trade is no exception. A 4-inch-square metal box is also known as a 1900 box, a 4-S box, or a 4-square box. The maximum number of conductors in the right section of Table 314.16(A) is based on the box not containing any fittings or devices, such as fixture studs, cable clamps, hickeys, switches, or receptacles. A few items within boxes are not counted such as cable connectors (if the clamping mechanism is outside the box), locknuts and bushings. Where the box contains fittings or devices, the number of conductors in the box must be reduced. Next month’s Code In Focus continues the discussion of box fill calculations. EC MILLER, owner of Lighthouse Educational Services, teaches classes and seminars on the electrical industry. He is the author of “Illustrated Guide to the National Electrical Code” and NFPA’s “Electrical Reference.” He can be reached at 615.333-3336, or www.charlesRmiller.com.
I. Scope and General Refer to this section in the NEC® for inclusions and exclusions. These are not permitted if locknuts or bushings are required on the side of the box. 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. These must be grounded.
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
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.
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.
(B) Box Fill Calculations.
(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.
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.
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.
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.
This section details methods of support. It indicates where they are needed and what can be used.
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®.
(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.
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
IV. Pull and Junction Boxes for Use on Systems Over 600 Volts, Nominal
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I. General
This type of cable is composed of insulated conductors in a flexible metal enclosure. Refer to 320.100. II. Installation It can be used exposed or concealed and in cable trays where so identified. It is permitted in dry locations and in plaster finish on brick or other masonry except in damp or wet locations. It can also be used in the voids of masonry block or tile walls when the walls are not exposed or subject to excessive moisture or dampness. There is a fine print note that this is not an all-inclusive list.
It cannot be used if subject to physical damage, in damp or wet locations, embedded in plaster finish on brick or any other masonry in damp or wet locations, in air voids of masonry block or tile when the walls are exposed to excessive dampness or moisture, or where it is exposed to corrosive vapors or fumes.
They must be made so that the cable will not be damaged and the radius of the curve of the inner edge cannot be less than five times the diameter of the cable.
III. Construction Specifications The cable consists of insulated conductors enclosed in a flexible metal tape armor with a copper or aluminum bonding strip inside and in contact with the armor.
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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I. General
II. Installation
III. Construction
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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I. General The wiring covered in this article is a field-installed system to be used for branch circuits under carpet squares. The reader is referred to the Code for these definitions.
II. Installation It can be used for general-purpose, appliance, and individual branch circuits; on floors that are hard, sound, or smooth made of materials like or similar to concrete, ceramic, composition, and wood; on walls in surface metal raceways; in damp locations; and on heated floors where the temperature is higher than 86°F if approved for those temperatures. The voltage ratings are up to 150 V to ground and up to 300 V between ungrounded conductors. The current ratings are up to 20 A for general-purpose and appliance branch circuits and up to 30 A for individual branch circuits. When on a floor, it must be covered with carpet squares. Release-type adhesive only is permitted. If it exceeds 2.3 mm (0.09 in.) above floor level it must be feathered or tapered at the edges to floor level. There are other requirements for corrosion resistance and metal-shield connectors.
It cannot be used outdoors, in wet locations, in classified hazardous locations, where there are corrosive vapors present, or in residential, school, or hospital buildings.
III. Construction
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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I. General
II. Installation
III. Construction Specifications
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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I. General
This cable is rated above 2000 V and is a single or multiconductor solid dielectric insulated cable. II. Installation It can be used in dry or wet locations, in raceways, directly buried in accordance with 300.50, in messenger supported wiring, and in cable trays in accordance with 392(B)(2).
It cannot be used in cable trays unless specified in 392.3(B)(2); nor can it be exposed to direct sunlight or buried unless as specified in 300.50 and unless it is identified for that purpose. III. Construction Specifications
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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I. General
Metal-clad cable is Type MC. It is a cable in which the conductors are enclosed in a corrugated metal sheath or interlocking metal tape, insulated, and the entire cable is put together at the factory. II. Installation This cable can be used for almost all types of applications, including wet locations, provided that it will not sustain physical damage and is not prohibited in another part of the NEC®. A listing is given in the NEC® for both general uses and specific uses. In wet locations one of the following must be adhered to: moisture will not get through the metal cover, a lead sheath that will not let moisture through is put under the metal cover, or the insulated conductors enclosed by the metal cover are listed for a wet location. Refer to this section in the Code. Type MC cable must be installed in accordance with the requirements of Articles 300, 490, 725, and Section 770.133. When installed in cable tray, direct buried, as service-entrance cable outside buildings or as aerial cable, you must refer to the appropriate articles in the NEC®.
This cable cannot be used in a location where it is subject to corrosive conditions that are destructive. The NEC® gives as examples direct buried cable in earth or concrete, under fills, chlorides, caustic alkalis, and the like.
It must comply with 300.4.
Must comply with 320.23. The following are the allowable radii of the curve of the inner edge: for shielded conductors, use the greater of either 12 times the diameter of one conductor or 7 times the overall diameter of the cable; for interlocked armor or corrugated sheath, 7 times the diameter of the sheath; for smooth sheath, use the following:
There are requirements for supported and unsupported cables.
Refer to 310.15 or 310.60 for 14 AWG and larger conductors. Use Table 402.5 for 18-16 AWG conductors. There are additional requirements for cable installed in cable tray and cable grouped together supported by messenger cable. C. Construction Specifications Copper, aluminum, or copper-clad aluminum must be used, either stranded or solid. The smallest sizes allowed are 18 AWG for copper and 12 AWG for aluminum or copper-clad aluminum.
The sheath must be either smooth, welded, and corrugated or interlocking. Page 8
I. General
Type MI cable is factory assembled with one or more conductors using a highly compressed refractory mineral insulation. The entire assembly is covered with a gastight and liquidtight continuous copper or alloy steel sheath. II. Installation It can be used for services, feeders, and branch circuits; power, control, lighting, and signal circuits; wet, dry, or continuously moist locations; exposed or concealed; indoors and outdoors; embedded in concrete, plaster, fill, and other masonry; hazardous locations; underground when protected; corrosive locations that will not harm the sheath; where exposed to gasoline and oil, in or attached to cable trays and in underground runs when protected against corrosion or physical damage.
Where exposed to corrosive materials that will harm the sheath unless it is properly protected and in underground runs unless it is protected against physical damage.
III. Construction Specifications Solid copper, nickel, or nickel-coated copper.
Highly compressed refractory mineral. Continuous construction that ensures mechanical protection and a moisture seal.
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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I. General
Nonmetallic-sheathed cable is a cable in which the insulated conductors are enclosed in a nonmetallic material that is moisture-resistant and flame-retardant. The cable is put together at the factory. There are definitions for NM, NMC, and NMS. II. Installation These types of cable can be used in one- and two-family dwellings, multifamily dwellings of types III, IV, and V construction except as noted in Section 334.12, and cable trays when they are noted for this use. These cables can also be used in other structures of Types III, IV, and V construction with limitations. Type NM cable can be used both in dry locations exposed and concealed as well as being fished in air voids of block and tile if it is not damp or moist. Type NMC cable can be used exposed or concealed in damp, dry, or corrosive locations, inside and outside of block walls, and in shallow chases protected against nails or screws. Type NMS can be used in the same locations as Type NM. The reader is referred to this section of the NEC® for a complete list of locations where these cables can be used.
Type NM, NMC, and NMS cannot be used in any dwelling not permitted in 334.10(1), (2), and (3); as service entrance cable; exposed in suspended or dropped ceilings in other than one family, two family, and multifamily dwellings; in commercial garages; in motion picture studios; in theatres and the like unless otherwise provided in the NEC®; in hoistways or on elevators or escalators; in storage battery rooms; in hazardous locations unless otherwise provided in the NEC®; and embedded in poured cement, concrete, or aggregate. There are additional limitations for Types NM and NMS cable. The reader is referred to this section of the NEC® for a complete list of locations where types NM, NMC, and NMS are not permitted.
The cable must be secured at least every 1.4 m (4½ ft.) and not more than 300 mm (12 in.) from a fitting, box, or cabinet. There are requirements for cable trays, unsupported cable, and wiring devices without a separate outlet box.
III. Construction Specifications
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I. General
This cable is factory assembled with a nonmetallic jacket containing two or more insulated conductors with or without bare or covered grounding conductors. II. Installation This cable can be used for power, lighting, control, and signal circuits; in cable trays, raceways, or supported by messenger wire; under certain conditions where permitted by Article 725 for Class 1 circuits; for nonpower-limited fire alarm circuits in accordance with Section 760.27; and for industrial establishments with qualified supervision and maintenance. There are additional requirements for support, identification, and equipment grounding in industrial locations. If installed in wet locations the cable must be resistant to moisture and corrosive agents.
Type TC cable cannot be used where exposed to physical damage; installed outside of a cable tray system or raceway unless permitted in 336.10(6); where exposed to direct sunlight unless sunlight resistant; and direct buried unless approved for that purpose.
III. Construction Specifications A metallic sheath cannot be put over or under the nonmetallic sheath. Metallic sheaths can be put over groups of conductors, under the outer jacket or both. Minimum-size conductors are 18 AWG for copper and 12 AWG for aluminum and copper-clad aluminum. Maximum size is 1000 kcmil. 14 AWG copper and larger and 12 AWG or larger aluminum or copper-clad aluminum are to be of the types shown in Table 310.13 or 310.62. (A) Fire Alarm Systems. It must be installed as noted in Section 760.27 for fire alarms systems. (B) Thermocouple Circuits. It must be installed as noted in Article 725, Part III. There are additional requirements. (C) Class 1 Circuit Conductors. When insulated conductors of sizes 18 AWG or 16 AWG copper are used, they shall be as noted in Section 725.27. The outer jacket must be a flame-retardant, nonmetallic material.
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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I. General
This cable is either Type SE or USE and is used primarily for services. Type SE has a flame-retardant and moisture-resistant cover. Type USE, which is the one used underground, has a moisture-resistant cover. II. Installation (A) Service-Entrance Conductors. When used as service- entrance conductors, you must follow 230.6, 230.7, and Parts II, III, and IV of Article 230. If protected as noted in Section 300.5(D), Type USE can come above ground outside in meter enclosures or terminations when used as a service lateral. (B) Branch Circuits or Feeders. (1) Grounded Conductor Insulated. Type SE can be used if all conductors are rubber-covered or thermoplastic type. (2) Grounded Conductor Not Insulated. Generally, Type SE cable can be used where the insulated conductor is used for circuit wiring in a building and where the uninsulated conductor is used only for equipment grounding. There is an exception. (3) Temperature Limitations. Do not exceed temperature specified. (4) Installation Methods for Branch Circuits and Feeders. Review applicable sections of the NEC®. III. Construction
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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I. General
A factory assembly with an integral covering of nonmetallic material for direct burial in the earth.
II. Installation It can be used for underground work including direct burial. Refer to 300.5 for underground requirements. If used as single conductor cables, all conductors of the feeder grounded conductor or branch circuit, including the grounded conductor and equipment grounding conductor, must conform to 300.3. It can be used for interior wiring in wet, dry, or corrosive areas provided that all other conditions are met. In certain of these cases, as described in Section 690.31, it can be used for solar photovoltaic systems. Single conductor cables can be nonheating leads for heating cable. If supported by cable trays, this cable must be multiconductor. If installed in accordance with Parts II and III of Article 334 it can be used as nonmetallic sheathed cable. In this case it must be multiconductor type.
This type of cable cannot be used for service entrances, in commercial garages, in theaters, in storage battery rooms, in motion picture studios, in hazardous locations, in hoistways, in poured cement except as permitted in 424.43, where exposed to direct rays of sun unless approved for sunlight installation, where subject to physical damage, or as an overhead cable except as messanger supported wiring.
Refer to 310.15, 60°C (140°F) conductors. III. Construction Specifications This cable is Type UF. Sizes allowed are minimum 14 AWG copper or 12 AWG aluminum or copper-clad aluminum and maximum 4/0 AWG.
The cable can have an insulated or bare conductor only for equipment grounding purposes. Moisture resistant type found in Table 310.13. If installed as a substitute for NM cable, the insulation must be rated at 90°C (194°F). Flame retardant; moisture, fugus, and corrosion resistant, suitable for direct burial in earth. Page 13
I. General
This conduit is a circular metal raceway threadable and designed for the protection and routing of conductors and cable. It can be used as an equipment grounding conductor with its couplings and fittings.
IMC, the factory elbows, couplings, and fittings must be listed. II. Installation Intermediate metal conduit can be used in most places and under most conditions. It can be used in the earth or in corrosive locations if it has corrosion protection. It can be used in cinder fill only if 50 mm (2 in.) of noncinder concrete is in direct contact, the conduit is 450 mm (18 in.) or more under the fill, or there is proper corrosion protection. In wet locations all supports, belts, screws, etc. must be protected against corrosion. With the exception of aluminum fittings and enclosures, dissimilar metals in contact must not be used where possible. The conduit used cannot be smaller than metric designator 16 (trade size ½) or larger than metric designator 103 (trade size 4). See 300.1(C) for metric designators.
Refer to Chapter 9, Table 1. Cables can be used if not prohibited by cable articles. Cable cannot exceed fill requirements of Table 1, Chapter 9. The conduit must not be injured. Refer to Table 2, Chapter 9, for the radius of the curve for field bends.
The maximum that is permitted is not more than 360° in bends between pull points.
All rough edges must be removed when the conduit is cut. When threaded in the field, a tapered cutting die with a taper of 1 in 16 (¾ in. taper per foot) must be used.
It must be installed as a complete system and fastened and supported as noted in (A) and (B) below. (A) Securely Fastened. It must be securely fastened within 900 mm (3 ft.) of all boxes, cabinets, conduits, or other conduit terminations. When structural members interfere with this, then the distance can be increased to 1.5 m (5 ft.). If approved, it does not have to be fastened within 900 mm (3 ft.) of a service head above a roof. (B) Supports. It has to be supported at intervals no longer than 3 m (10 ft.). Table 344.30(B)(2) indicates the spacing of supports for straight runs of conduit with the proper couplings and there is a prevention of the transmission of stresses. Exposed vertical risers can be supported at intervals of 6 m (20 ft.), if the couplings are threaded, firmly supported at top and bottom, and there is no other intermediate support available. Horizontal runs that are supported by framing members not longer than 3 m (10 ft.) apart with supports within 900 mm (3 ft.) of the terminations are permitted.
Threadless couplings and connectors can be used and should be made tight. Comply with 314.15(A). Running threads cannot be used. Use concrete type in concrete and in wet areas. Do not use threadless couplings and connectors on threaded conduit unless it is listed for that use. A bushing must be used at the point where the conduit goes into a box, fitting, or other enclosure. This is to protect the wire. An exception is made if protection is provided with the box or fitting. They are permitted only if made in accordance with Section 300.15. III. Construction Specifications The conduit must be marked every 1.5 m (5 ft.) with the letter IMC and as required by 110.24. This type of conduit has a standard length of 3 m (10 ft.) with one coupling and both ends threaded. Shorter or longer lengths with or without couplings or threads are permitted. Page 14
I. General
Rigid metal conduit is a raceway that is listed, has a cross section that is circular, has integral or associated couplings, is used with listed fittings to give electrical continuity, and is approved for the installation of electrical conductors.
This type of conduit, associated fittings, factory elbows and couplings must be listed. II. Installation (A) All Atmospheric Conditions and Occupancies. It is permitted in all atmospheric conditions and all occupancies. If the conduit's protection against corrosion is only enamel, it can be used only indoors and in areas that do not have severe corrosive problems. Aluminum enclosures and fittings can be used with steel conduit and vice versa. (B) Corrosion Environments. If the conduit is protected from corrosion and is suitable, the conduit, elbows, couplings, and fittings can be installed in concrete, in areas where there is a severe corrosive problem, and in direct contact with the earth. (C) Cinder Fill. It cannot be used in or under cinder fill when there may be permanent moisture unless it is suitable for this type of installation, there are 50 mm (2 in.) or more of noncinder concrete all around it, it is at least 450 mm (18 in.) under the fill, or where it is suitable for the condition and has corrosion protection. (D) Wet Locations. Everything must be corrosion-resistant (bolts, straps, etc.). Contact between dissimilar metals must be avoided where possible to eliminate galvanic action. Aluminum fittings are permitted with steel and vice versa where not subject to severe corrosion. Metric designator 16 (trade size ½) is the minimum size permitted unless used for enclosing motor leads [see Section 430.145(B)]. The maximum size permitted is metric designator 155 (trade size 6). See 300.1(C) for metric designators.
Refer to Chapter 9, Table 1. Cables can be used if not prohibited by cable articles. Cable cannot exceed fill requirements of Table 1, Chapter 9. The conduit must not be damaged and the internal diameter will not be reduced. Refer to Table 2, Chapter 9, for the radius to the center line of the conduit for field bends.
The maximum that is permitted is not more than 360° in bends between pull points.
All rough edges must be removed when the conduit is cut. When threaded in the field, a tapered cutting die 1 in 16 taper (¾ in. taper per foot) must be used.
The conduit must be supported at intervals no longer than 3 m (10 ft.) and fastened not more than 900 mm (3 ft.) from a box, fitting, etc. It must be installed as a complete system in accordance with 300.18. Fastening can be increased to 1.5 m (5 ft.) where structural members do not permit fastening within 900 mm (3 ft.). For supports for straight runs with threaded couplings, refer to Table 344.30(B)(2). No stress is to be transmitted to the terminations. Vertical risers from industrial machinery or fixed equipment can have the distance between supports at 6 m (20 ft.) if the conduit uses threaded couplings and is properly supported at the top and bottom. Where approved, the conduit does not have to be fastened within 900 mm (3 ft.) of a service head for a termination of a mast above the roof. Horizontal runs that are supported by openings through framing members not less than 3 m (10 ft.) and fastened within 900 mm (3 ft.) of termination points are permitted.
Threadless couplings and connectors can be used and made tight. Running threads cannot be used. Use concrete type in masonry or concrete. Comply with 314.15(A) in wet locations. Do not use threadless couplings and connectors on threaded conduit unless it is listed for that use. A bushing must be used at the point where the conduit goes into a box, fitting, or other enclosure. This is to protect the wire. An exception is made if protection is provided with the box or fitting. Refer to Article 300.15. It is permitted as an equipment grounding conductor. III. Construction Specifications If the conduit is nonferrous of corrosion-resistant material, it must be marked to indicate it. At every 3 m (10 ft.) the conduit must be marked with identification (refer to Section 110.21). This type of conduit has a standard in length of 3 m (10 ft.) including one attached coupling. It has to be threaded at each end. Smaller and larger lengths can be used with or without couplings and threads. Page 15
I. General
This is a circular raceway of helically wound, formed, interlocked metal strip.
Must be listed. II. Installation It can be used in exposed and concealed locations.
It cannot be used in wet locations unless approved for this and the liquid does not get into the conduit, in hoistways unless permitted by Section 620.21(A)(1), in storage battery rooms, in hazardous locations unless allowed by Sections 501.4(B) and 504.20, where materials might deteriorate conductors, underground or in poured concrete or aggregate, and where subject to physical damage. Minimum size permitted is metric designator 12 (trade size 3/8). The use of metric designator 12 (3/8) is allowed for leads to motors [Section 430.145(b)], not longer than 1.8 m (6 ft.) as part of a listed assembly or taps to lighting fixtures [Section 410.67(C)] or utilization equipment, for manufactured wiring systems [Section 604.6(A)], in hoistways Section 620.21, and as permitted by Section 410.77(C) as part of a listed assembly to connect wired fixture sections. There are five exceptions. The maximum size permitted is metric designator 103 (trade size 4).
Cannot exceed the percentage fill of Table 1, Chapter 9. Cables can be used if not prohibited by cable articles. Cable cannot exceed the fill requirements of Table 1, Chapter 9. Bends must not damage the conduit and must not reduce the internal diameter of the conduit. Bends can be made with auxiliary equipment manually. The radius of the curve to the centerline can not be less than that shown in Table 1, Chapter 9. Use the "Other Bends" column.
The maximum number that is permitted is not more than 360 degrees in bends between pull points. The radius of curve of the inner edge of a field bend must comply with Table 346.10.
Securely fasten within 300 mm (12 in.) of a termination point and supports must be not more than 1.4 m (4½ ft.) apart. There is a provision for supports through framing openings. There are four exceptions.
They can be made only in accordance with 300.15.
An equipment grounding conductor must be installed when the conduit is used to connect equipment where flexibility is needed. It can be used as an equipment grounding conductor where flexibility is not required in accordance with 250.48(5) or (6). The equipment grounding conductor must be installed in accordance with 250.134(B). Equipment bonding conductors must be installed in accordance with 250.102. Page 16
I. General
This conduit is similar to flexible metal conduit, but it has a jacket over the metal conduit. The jacket is liquidtight, nonmetallic, and sunlight-resistant.
II. Installation This conduit can be installed exposed or concealed, directly buried in earth and if protection from liquids, vapor, or solids is necessary or if flexibility is desired. It can be installed in hazardous areas if approved for that installation. Refer to Sections 501.4(B), 502.4, 503.3, 504.20, and 553.7(B).
It cannot be installed when subject to damage or where temperatures exceed that which is approved for the material. Minimum metric designator 16 (trade size ½). For exceptions, refer to Section 348.20(A). The maximum size allowed is metric designator 103 (trade size 4). Refer to 300.1(C) for metric designators and trade sizes.
(A) Metric Designators 16 through 103 (Trade Sizes ½ through 4). Refer to Table 1, Chapter 9. Cables can be used if not prohibited by cable articles. Cables cannot exceed the fill requirements of Table 1, Chapter 9. (B) Metric Designator 12 (Trade Size 3/8). Refer to the Fittings Outside Conduit columns in Table 348.22. Bends must not damage the conduit and must not reduce the internal diameter of the conduit. Bends can be made with auxiliary equipment manually. The radius of the curve to the centerline can not be less than that shown in Table 2, Chapter 9. Use the "Other Bends" column.
The maximum that is permitted is not more than 360° in bends between pull points.
It must be supported and secured not more than 1.4 m (4½ ft.) apart. It must be securely fastened within 300 mm (12 in.) of a conduit termination. Four exceptions are for when the conduit is fished, where flexibility is needed, length not exceeding 900 mm (3 ft.) at terminals, lengths not exceeding 1.8 m (6 ft.) from a fixture terminal connection for tap conductors to a lighting fixture as noted in Section 410.67(C) and within accessible ceilings for lengths not exceeding 1.8 m (6 ft.) from the last point where the raceway is fastened, for connections to luminaires or other equipment. Horizontal runs allowed to be supported by the openings in framing members not more than 1.4 m (4½ ft.) apart and fastened within 300 mm (12 in.) of a termination.
They can be made only in accordance with Section 300.15.
This type of conduit can be used as a means of grounding under certain conditions. Refer to the NEC®. III. Construction Specifications Page 17
I. General
A conduit which is circular in cross section and made from a nonmetallic material.
The RNC, elbows, and associated fittings must be listed. II. Installation Some of the uses permitted and other references in the NEC® are: concealed in walls, floors, ceilings, and cinder fill; exposed when not subject to injury; in corrosive locations where approved for that type of location and in accordance with Section 300.6; in dry and damp locations in accordance with Section 352.12; in wet locations where the entire system is installed to prevent water from getting into the conduit and all bolts, screws, and so forth are corrosion resistant and underground in accordance with Sections 300.5 and 300.50. There is a provision for use as a support in certain specific cases.
This type of conduit must not be used in hazardous locations except where permitted by Sections 503.10(A), 504.20, 514.8 exception 2, 515.8, and the Class 1, Division 2 locations in Section 501.10(B)(3); in areas where there might be physical damage to the conduit; in theaters and similar locations except as noted in Articles 518 and 520; where the temperature rating of the conduit is exceeded by that of the conductor insulation; in areas where the ambient temperature exceeds 50°C (122°F) unless otherwise listed; and for supporting fixtures or other equipment not described in 352.10(H). The minimum size is metric designator 16 (trade size ½). The maximum size is metric designator 155 (trade size 6).
Cannot exceed the percentage fill of Table 1, Chapter 9. Cables can be used if not prohibited by cable articles. Cable cannot exceed the fill requirements of Table 1, Chapter 9. The conduit must not be injured. Refer to Table 2, Chapter 9.
The maximum that is permitted is not more than 360° in bends between pull points. Remove rough edges on cuts.
Refer to Section 300.18 and Table 352.30(B) for spacing of supports. It must be fastened no farther than 900 mm (3 ft.) from a termination point. If it is listed for other securing spacing, it is permitted to follow but not exceed the listing. There is an exception for supports by openings through framing members of horizontal runs.
Expansion fittings have to be provided to compensate for thermal expansion and contraction where the change in length according to Table 352.44(A) or (B) will be 6 mm (¼ in.) or greater between securely mounted conduit terminations.
A bushing must be used at the point where the conduit goes into a box or fitting unless protection is provided in the box or fitting. Use approved methods. They are permitted only in accordance with Section 300.15. A separate equipment grounding conductor must be installed where equipment grounding is required. There are two exceptions. III. Construction Specifications RNC and fittings must be composed of a nonmetallic material. It must be resistant to moisture and chemical atmospheres. Above ground it must be flame resistant, resistant to impact and crushing, resistant to distortion from heat, and resistant to low temperature and sunlight. Below ground it must be resistant to corrosive agents and moisture, be able to withstand crushing and other abuse. If it is direct buried without encasement in concrete, it must be able to resist the continued loading it will encounter. It must be marked at least every 3 m (10 ft.) in each length. There are requirements for marking on conduit used above and below ground. Page 18
I. General
A conduit that is circular in cross section with its associated couplings, connectors, etc. that is nonmetallic and used for the installation of electrical conductors.
II. Installation In can be used in cinder fill; in continuous lengths from a reel or discrete lengths; in areas that are corrosive as noted in 300.6 and where the conduit is listed for use where subject to certain chemicals; and for direct burial in earth or concrete (refer to 300.5 and 300.50 for underground installations).
It cannot be used where exposed; in hazardous (classified) locations unless permitted in 504.20; within a building; in ambient temperatures higher than 50°C (122°F) unless listed for higher; for conductors or cables operating at a higher temperature than the conduit listed operating temperature. There is an exception. You cannot use a smaller size than metric designator 16 (trade size ½) or larger than metric designator 103 (trade size 4).
Cannot exceed the percentage fill of Table 1, Chapter 9. Cables can be used if not prohibited by the cable articles. Cable cannot exceed the fill requirements of Table 1, Chapter 9. They must be manually made and must not be damaged. Refer to Table 354.24.
The maximum that is permitted is not more than 360° in bends between termination points. Remove rough edges. A bushing must be used at the point where the conduit goes into a box or fitting unless protection is provided in the box or fitting. Use approved methods. They are permitted only in accordance with Section 300.15. A separate equipment grounding conductor must be installed where equipment ground is required. There are two exceptions. III. Construction Specifications This conduit must be composed of nonmetallic material and must be resistant to moisture and chemical atmospheres. It must be resistant to moisture and corrosive agents. It must be strong enough to withstand abuse during installation. If used for direct burial without being encased in concrete, it must be able to withstand the continued loading after installation. It must be marked at least every 3 m (10 ft.) as noted in 110.21. The marking must include the type of material.
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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I. General
This is a factory assembly of conductors or cables in a nonmetallic circular conduit.
II. Installation It can be used encased or embedded in concrete, in cinder fill, for direct burial cable with cover requirements as noted in Tables 300.5 and 300.50 under rigid nonmetallic conduit, and in underground locations subject to corrosive action as noted in Section 300.6 and where subject to chemicals when the assembly is approved for it.
It cannot be used in exposed locations, inside buildings with one exception, and in hazardous (classified) locations except as noted in Sections 503.3(A), 504.20, 514.8, 515.8, and 501.4(B). It cannot be smaller than metric designator 16 (trade size ½) or larger than metric designator 103 (trade size 4).
Not to exceed number shown in Table 1 of Chapter 9. They must be made manually; the conduit must not be damaged and the internal diameter must not be reduced. Refer to Table 354.24.
The maximum is not more than 360° between termination points.
III. Construction Specifications
Must be marked every 3.05 m (10 ft.). It also must be identified on a tag at each end of the assembly or on the side of the reel.
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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This conduit has a circular cross section. It comes in various types. It can have a smooth inner surface with integral reinforcement; smooth seamless inner core and cover bonded together with the reinforcement between the core and cover; or corrugated surfaces without reinforcement within the walls (Type LFNC-C). This type of conduit is flame-resistant and is approved for electrical conductors, with fittings.
II. Installation This conduit can be installed exposed or concealed if protection from vapors, liquids, or solids is necessary, if flexibility is desired, or for outdoors if listed and marked for this purpose. It can also be used outdoors when listed and suitable and for direct burial use when listed and marked, as well as in lengths longer than 1.8 m (6 ft.), where additional length is essential. It can be used as a prewired assembly under certain conditions.
It can not be installed if subject to damage, when temperatures will exceed those for which the conduit is approved, in lengths in excess of 1.8 m (6 ft.) except under certain conditions, where voltages are higher than 600 V. except as per 600.32(A), and in a hazardous location except as per 501.10(B), 502.10(A) & (B), 503.10(A), and 504.20. Metric designator 16 (trade size ½) to metric designator 103 (trade size 4). For leads of motors metric designator 12 (3/8) can be used in accordance with 430.145(B). There are two other exceptions.
Cannot exceed the percentage of fill of Table 1, Chapter 9. Cables can be used if not prohibited by cable articles. Cable cannot exceed the fill requirements of Table 1, Chapter 9. They must be made so that the conduit is not damaged and the internal diameter must not be reduced. Refer to Table 2, Chapter 9, for the radius of curve to the center line.
The maximum that is permitted is not more than 360.
Can only be made in accordance with 300.15.
An equipment grounding conductor must be installed. III. Construction Specifications
Page 21
I. General
It is a thinwall listed metallic tubing, circular, with a cross-sectional area that is approved when joined together with listed fittings, for the installation of electrical conductors.
II. Installation It can be used for both exposed and concealed work. Both ferrous and nonferrous tubing and fittings can be installed in concrete, in areas subject to severe corrosion, and in direct contact with the earth if protected against corrosion and suitable for the condition. It can be installed in wet locations if all supports, bolts, etc. are corrosion resistant or covered with corrosion resistant material.
It cannot be used where it will be subject to severe damage, where protected from corrosion by only enamel, in cinder concrete or cinder fill where there is permanent moisture unless there is a layer of noncinder concrete on all sides at least 50 mm (2 in.) thick or the tubing is at least 450 mm (18 in.) under the fill, to support fixtures or equipment except conduit bodies not larger than the largest trade size of the tubing, or in hazardous locations except as permitted in Sections 502.4, 503.3, and 504.20. Where possible, there should be no contact between dissimilar metals in the system. The minimum size permitted is metric designator 16 (trade size ½) unless used for enclosing motor leads [see Section 430.145(B)]. The maximum size permitted is metric designator 103 (trade size 4).
Cannot exceed the percentage fill requirements of Table 1, Chapter 9. Cables can be used if not prohibited by cable articles. Cable cannot exceed the fill requirements of Table 1, Chapter 9. The tubing must not be injured and the internal diameter is not reduced. Refer to Table 2, Chapter 9, for the radius of the center line of a field bend.
The maximum that is permitted is not more than 360° in bends between pull points.
Threading is not permitted except on factory-threaded integral couplings. Remove rough edges of all cuts.
The tubing must be installed as a complete system as noted in Article 300.18. It must be fastened and supported in accordance with 358.30(A) and (B). The tubing must be fastened at intervals no longer than 3 m (10 ft.) and not more than 900 mm (3 ft.) from a box, fitting, etc. The 900 mm (3-ft.) rule may be extended to 1.5 m (5 ft.) for unbroken lengths where structural members interfere at 900 mm (3 ft.). There is an exception for concealed work. EMT in horizontal runs supported by openings through framing not more than 3 m (10 ft.) and fastened within 900 mm (3 ft.) of termination is permitted.
They must be tight and concrete-tight if used in concrete and comply with 314.15(A) if used in wet locations. They are to be made in accordance with Section 300.15. EMT is permitted as an equipment grounding conductor. III. Construction Specifications If an integral threaded coupling is used, threads for both the couplings and tubing must be factory made. The EMT threads and couplings can not bend the tubing at any part of the thread. It must be clearly and durable marked at least every 3 m (10 ft.) on accordance with 110.21. Page 22
I. General
It is flexible, metallic, circular in cross section, and liquidtight without a nonmetallic jacket.
II. Installation This type of tubing can be used for branch circuits in dry locations, in accessible locations, concealed, and not more than nominal 1000-V systems.
It cannot be used where subject to physical damage, in hoist-ways, storage battery rooms, hazardous locations, embedded in concrete, or directly buried in the earth. Lengths larger than 1.8 m (6 ft.) are not permitted. The minimum size permitted is metric designator 16 (trade size ½) except that metric designator 12 (trade size 3/8) can be used in accordance with Section 300.22(B) and (C) or part of an approved lighting fixture assembly in accordance with Section 410.67(C) and not more than 1.8 m (6 ft.) in length. The maximum size permitted is metric designator 21 (trade size ¾).
Refer to Chapter 9, Table 1, for the number of conductors permitted in metric designator 16 (trade size ½) and metric designator 21 (trade size ¾) tubing. Cables are permitted if not prohibited by cable articles. The number of cables cannot exceed what is allowed in Chapter 9, Table 1. Refer to Table 348.22 for the number of conductors permitted in metric designator 12 (trade size 3/8) tubing. If the tubing is bent infrequently after installation, refer to Table 360.24(A) in the NEC®. If the tubing is bent for installation, use Table 360.24(B) in the NEC®.
It is permitted as an equipment grounding conductor only in accordance with 250.118(B) III. Construction Specifications Mark in accordance with 110.21. Page 23
I. General
II. Installation
III. Construction Specifications
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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If they are used outdoors they must be listed for use in wet locations, exposure to sunlight, and the maximum ambient temperature that they will be used in. If they are used indoors they must be listed for the maximum ambient temperature that they will be used in. II. Installation Auxiliary gutters can be used to supplement wiring spaces at meters, switchboards, and similar places as well as enclosed conductors or busbars.
They cannot be used to enclose equipment, switches, overcurrent devices, or similar equipment. They must not extend more than 9 m (30 ft.) from the equipment they supplement.
Not more than 30 conductors are allowed at any point without the derating factor of 310.15(B)(2)(a) and the area of the conductors cannot be more than 20% of the area of a sheet metal auxiliary gutter. For signaling or motor controller circuits where the conductors are used only for starting duty, they are not considered current carrying conductors. The area of the conductors in a nonmettalic auxiliary gutter cannot be more than 20% of the area of the gutter.
The following refer to sheet metal auxiliary gutters. When there are not more than 30 current-carrying conductors, the derating factors for ampacities do not have to be applied. The capacities of bars cannot exceed 1.55 A per square millimeter (1000 A per square inch) for copper and 1.09 A per mm2 (700 A per square inch) for aluminum. For nonmetallic auxiliary gutters, use the derating factors in Section 310.15(B)(2)(a).
Metal gutters must be grounded. III. Construction Specifications
The following article titles are listed for reference: Article 368Busways. Article 370Cablebus. Article 372Cellular Concrete Floor Raceways.
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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This is a raceway system that is part of the entire floor and installed as such. A complete definition of terms is given in the NEC®. I. Installation Not larger than 1/0 AWG unless special permission is obtained.
Not more than 40% fill.
II. Construction Specifications The following article titles are listed for reference: Article 376Metal Wireways; Article 378Nonmetallic Wireways
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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I. General
This is a conductor arrangement with two insulated conductors in a nonmetallic jacket or thermoplastic cover. II. Installation Only from an existing 15- or 20-A outlet on a branch circuit. It must be run exposed and dry. For surface extensions the buildings must only be occupied for residential or office use and with height restrictions of three floors above grade.
This type of extension cannot be used in unfinished areas, where there are corrosive vapors, through a floor or partition; and where the voltage between conductors is greater than 150 V for surface work and 300 V for aerial cable.
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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What article has the title outlet device pull and junction boxes conduit bodies fittings and Handhole enclosures?
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