Philippine Electrical Code Part 1/Chapter 3. Wiring Methods and Materials/Article 3.0 - Wiring Methods

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Article 3.0 - Wiring Methods

DISCLAIMER
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.


While the authors have used good faith and efforts to ensure that the information and instructions contained in this work are accurate, the authors disclaim all responsibility for errors or omissions, including without limitation responsibility for damages resulting from the use of or reliance on this work. Use of the information and instructions contained in this work is at your own risk. If any contents or other technology this work contains or describes is subject to open source licenses or the intellectual property rights of others, it is your responsibility to ensure that your use thereof complies with such licenses and/or rights

Note: This is a work in progress...

Contents


3.0.1 General Requirements

3.0.1.1 Scope.

(a) All Wiring Installations.

This article covers wiring methods for all wiring installations unless modified by other articles.

(b) Integral Parts of Equipment.

The provisions of this article are not intended to apply to the conductors that form an integral part of equipment, such as motors, controllers, motor control centers, or factory assembled control equipment or listed utilization equipment.

(c) Metric Designators and Trade Sizes.

Metric designators and trade sizes for conduit, tubing, and associated fittings and accessories shall be as designated in Table 3.0.1.1(c).

3.0.1.2 Limitations.

(a) Voltage.

Wiring methods specified in Chapter 3 shall be used for 600 volts, nominal, or less where not specifically limited in some section of Chapter 3. They shall be permitted for over 600 volts, nominal, where specifically permitted elsewhere in this Code.

(b) Temperature.

Temperature limitation of conductors shall be in accordance with 3.10.1.10.


Table 3.0.1.1(c) Metric Designator and Trade Sizes
Metric Designator Trade Size

12

16

½

21

¾

27

1

35

41

53

2

63

78

3

91

103

4

129

5

155

6

Note: The metric designators and trade sizes are for identification purposes only and are not actual dimension


3.0.1.3 Conductors.

(a) Single Conductors.

Single conductors specified in Table 3.10.1.13 shall only be installed where part of a recognized wiring method of Chapter 3.

Exception: Individual conductors shall be permitted where installed as separate overhead conductors in accordance with 2.25.1.6.

(b) Conductors of the Same Circuit.

All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors and bonding conductors shall be contained within the same raceway, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord, unless otherwise permitted in accordance with 3.0.1.3(b)(1) through (b)(4).

(1) Paralleled Installations.

Conductors shall be permitted to be run in parallel in accordance with the provisions of 3.10.1.4. The requirement to run all circuit conductors within the same raceway, auxiliary gutter, cable tray, trench, cable, or cord shall apply separately to each portion of the paralleled installation, and the equipment grounding conductors shall comply with the provisions of 2.50.6.3. Parallel runs in cable tray shall comply with the provisions of 3.92.1.8(d).

Exception: Conductors installed in nonmetallic raceways run underground shall be permitted to be arranged as isolated phase installations. The raceways shall be installed in close proximity, and the conductors shall comply with the provisions of 3.0.1.20(b).

(2) Grounding and Bonding Conductors

Equipment grounding conductors shall be permitted to be installed outside a raceway or cable assembly where in accordance with the provisions of 2.50.7.1(c) for certain existing installations or in accordance with 2.50.7.5(b), Exception No. 2, for dc circuits. Equipment bonding conductors shall be permitted to be installed on the outside of raceways in accordance with 2.50.5.3(e).

(3) Nonferrous Wiring Methods

Conductors in wiring methods with a nonmetallic or other nonmagnetic sheath, where run in different raceways, auxiliary gutters, cable trays, trenches, cables, or cords, shall comply with the provisions of 3.0.1.20(b). Conductors in single- conductor Type MI cable with a nonmagnetic sheath shall comply with the provisions of 3.32.2.22. Conductors of single-conductor Type MC cable with a nonmagnetic sheath shall comply with the provisions of 3.30.2.22, 3.30.3.13, and 3.0.1.20(b).

(4) Enclosures

Where an auxiliary gutter runs between a column- width panelboard and a pull box, and the pull box includes neutral terminations, the neutral conductors of circuits supplied from the panelboard shall be permitted to originate in the pull box.

(c) Conductors of Different Systems.
(1) 600 Volts, Nominal, or Less

Conductors of circuits rated 600 volts, nominal, or less, ac circuits, and dc circuits shall be permitted to occupy the same equipment wiring enclosure, cable, or raceway. All conductors shall have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the enclosure, cable, or raceway.

Exception: For solar photovoltaic systems in accordance with 6.90.1.4(b).

FPN: See 7.25.3.15(a) for Class 2 and Class 3 circuit conductors. (2) Over 600 Volts, Nominal. Conductors of circuits rated over 600 volts, nominal, shall not occupy the same equipment wiring enclosure, cable, or raceway with conductors of circuits rated 600 volts, nominal, or less unless otherwise permitted in (c)(2)(a) through (c)(2)(e).

a. Secondary wiring to electric-discharge lamps of 1000 volts or less, if insulated for the secondary voltage involved, shall be permitted to occupy the same luminaire (fixture), sign, or outline lighting enclosure as the branch-circuit conductors.
b. Primary leads of electric-discharge lamp ballasts insulated for the primary voltage of the ballast, where contained within the individual wiring enclosure, shall be permitted to occupy the same luminaire (fixture), sign, or outline lighting enclosure as the branch- circuit conductors.
c. Excitation, control, relay, and ammeter conductors used in connection with any individual motor or starter shall be permitted to occupy the same enclosure as the motor-circuit conductors.
d. In motors, switchgear and control assemblies, and similar equipment, conductors of different voltage ratings shall be permitted.
e. In manholes, if the conductors of each system are permanently and effectively separated from the conductors of the other systems and securely fastened to racks, insulators, or other approved supports, conductors of different voltage ratings shall be permitted. Conductors having nonshielded insulation and operating at different voltage levels shall not occupy the same enclosure, cable, or raceway.

3.0.1.4 Protection Against Physical Damage.

Where subject to physical damage, conductors shall be protected.

(a) Cables and Raceways Through Wood Members.
(1) Bored Holes.

In both exposed and concealed locations, where a cable- or raceway-type wiring method is installed through bored holes in joists, rafters, or wood members, holes shall be bored so that the edge of the hole is not less than 30 mm from the nearest edge of the wood member. Where this distance cannot be maintained, the cable or raceway shall be protected from penetration by screws or nails by a steel plate or bushing, at least 1.60 mm thick, and of appropriate length and width installed to cover the area of the wiring.

Exception No. 1: Steel plates shall not be required to protect rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing.

Exception No. 2: A listed and marked steel plate less than 1.60 mm thick that provides equal or better protection against nail or screw penetration shall be permitted.

(2) Notches in Wood.

Where there is no objection because of weakening the building structure, in both exposed and concealed locations, cables or raceways shall be permitted to be laid in notches in wood studs, joists, rafters, or other wood members where the cable or raceway at those points is protected against nails or screws by a steel plate at least 1.60 mm thick, and of appropriate length and width, installed to cover the area of the wiring. The steel plate shall be installed before the building finish is applied.

Exception No. 1: Steel plates shall not be required to protect rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing.

Exception No. 2: A listed and marked steel plate less than 1.60 mm thick that provides equal or better protection against nail or screw penetration shall be permitted.

(b) Nonmetallic-Sheathed Cables and Electrical Nonmetallic Tubing Through Metal Framing Members.
(1) Nonmetallic-Sheathed Cable.

In both exposed and concealed locations where nonmetallic-sheathed cables pass through either factory or field punched, cut, or drilled slots or holes in metal members, the cable shall be protected by listed bushings or listed grommets covering all metal edges that are securely fastened in the opening prior to installation of the cable.

(2) Nonmetallic-Sheathed Cable and Electrical Nonmetallic Tubing.

Where nails or screws are likely to penetrate nonmetallic- sheathed cable or electrical nonmetallic tubing, a steel sleeve, steel plate, or steel clip not less than 1.60 mm in thickness shall be used to protect the cable or tubing.

Exception: A listed and marked steel plate less than 1.60 mm thick that provides equal or better protection against nail or screw penetration shall be permitted.

(c) Cables Through Spaces Behind Panels Designed to Allow Access.

Cables or raceway-type wiring methods, installed behind panels designed to allow access, shall be supported according to their applicable articles.

(d) Cables and Raceways Parallel to Framing Members and Furring Strips.

In both exposed and concealed locations, where a cable- or raceway-type wiring method is installed parallel to framing members, such as joists, rafters, or studs, or is installed parallel to furring strips, the cable or raceway shall be installed and supported so that the nearest outside surface of the cable or raceway is not less than 30 mm from the nearest edge of the framing member or furring strips where nails or screws are likely to penetrate. Where this distance cannot be maintained, the cable or raceway shall be protected from penetration by nails or screws by a steel plate, sleeve, or equivalent at least 1.60 mm thick.

Exception No. 1: Steel plates, sleeves, or the equivalent shall not be required to protect rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing.

Exception No. 2: For concealed work in finished buildings, or finished panels for prefabricated buildings where such supporting is impracticable, it shall be permissible to fish the cables between access points.

Exception No. 3: A listed and marked steel plate less than 1.60 mm thick that provides equal or better protection against nail or screw penetration shall be permitted.

(e) Cables and Raceways Installed in Shallow Grooves.

Cable- or raceway-type wiring methods installed in a groove, to be covered by wallboard, siding, paneling, carpeting, or similar finish, shall be protected by 1.60 mm thick steel plate, sleeve, or equivalent or by not less than 30 mm free space for the full length of the groove in which the cable or raceway is installed.

Exception No. 1: Steel plates, sleeves, or the equivalent shall not be required to protect rigid metal conduit, intermediate metal conduit, rigid nonmetallic conduit, or electrical metallic tubing.

Exception No. 2: A listed and marked steel plate less than 1.60 mm thick that provides equal or better protection against nail or screw penetration shall be permitted.

(f) Insulated Fittings.

Where raceways containing ungrounded conductors 22 mm 2 or larger enter a cabinet, box enclosure, or raceway, the conductors shall be protected by a substantial fitting providing a smoothly rounded insulating surface, unless the conductors are separated from the fitting or raceway by substantial insulating material that is securely fastened in place.

Exception: Where threaded hubs or bosses that are an integral part of a cabinet, box enclosure, or raceway provide a smoothly rounded or flared entry for conductors.

Conduit bushings constructed wholly of insulating material shall not be used to secure a fitting or raceway. The insulating fitting or insulating material shall have a temperature rating not less than the insulation temperature rating of the installed conductors.

3.0.1.5 Underground Installations. =

(a) Minimum Cover Requirements.

Direct-buried cable or conduit or other raceways shall be installed to meet the minimum cover requirements of Table 3.0.1.5.

(b) Listing

Cables and insulated conductors installed in enclosures or raceways in underground installations shall be listed for use in wet locations.

(c) Underground Cables Under Buildings.

Underground cable installed under a building shall be in a raceway that is extended beyond the outside walls of the building.

(d) Protection from Damage.

Direct-buried conductors and cables shall be protected from damage in accordance with 3.0.1.5(d)(1) through (d)(4).

(1) Emerging from Grade.

Direct-buried conductors and enclosures emerging from grade shall be protected by enclosures or raceways extending from the minimum cover distance below grade required by 3.0.1.5(a) to a point at least 2 400 mm above finished grade. In no case shall the protection be required to exceed 450 mm below finished grade.

(2) Conductors Entering Buildings.

Conductors entering a building shall be protected to the point of entrance.

(3) Service Conductors.

Underground service conductors that are not encased in concrete and that are buried 450 mm or more below grade shall have their location identified by a warning ribbon that is placed in the trench at least 300 mm above the underground installation.

(4) Enclosure or Raceway Damage.

Where the enclosure or raceway is subject to physical damage, the conductors shall be installed in rigid metal conduit, intermediate metal conduit, Schedule 80 rigid nonmetallic conduit, or equivalent.

(e) 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 in accordance with 1.10.1.14(b).

(f) Backfill.

Backfill that contains large rocks, paving materials, cinders, large or sharply angular substances, or corrosive material shall not be placed in an excavation where materials may damage 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 running boards, suitable sleeves, or other approved means.

(g) Raceway Seals.

Conduits or raceways through which moisture may contact live parts shall be sealed or plugged at either or both ends.

FPN: Presence of hazardous gases or vapors may also necessitate sealing of underground conduits or raceways entering buildings.

Table 3.0.1.5 Minimum Cover Requirements, 0 to 600 Volts, Nominal, Burial in Millimeters
Location of Wiring Method or Circuit Type of Wiring Method or Circuit
Column 1 Direct Burial Cables or Conductors (mm) Column 2 Rigid Metal Conduit or Intermediate Metal Conduit (mm) Column 3 Nonmetallic Raceways Listed for Direct Burial Without Concrete Encasement or Other Approved Raceways (mm) Column 4 Residential Branch Circuits Rated 120 Volts or Less with GFCI Protection and Maximum Overcurrent Protection of 20 Amperes (mm) Column 5 Circuits for Control of Irrigation and Landscape Lighting Limited to Not More Than 30 Volts and Installed with Type UF or in Other Identified Cable or Raceway (mm)
All locations not specified below 600 150 450 300 150
In trench below 50 mm thick concrete or equivalent 150 300 150 150
Under a building 0
(in raceway only)
0 0 0
(in raceway only)
0
(in raceway only)
Under minimum of 100 mm thick concrete exterior slab with no vehicular traffic and the slab extending not less than 150 mm beyond the underground installation 450 100 100 150
(direct burial)
100
(in raceway)
150
Under minimum of 100 mm thick concrete exterior slab with no vehicular traffic and the slab extending not less than 150 mm beyond the underground installation 450 100 100 150
(direct burial)
100
(in raceway)
150
Under streets, highways, roads, alleys, driveways, and parking lots 600 600 600 600 600
One- and two-family dwelling driveways and outdoor parking areas, and used only for dwelling-related purposes 450 450 450 450 450
In or under airport runways, including adjacent areas where trespassing prohibited 450 450 450 450 450
Notes:
1. Cover is defined as the shortest distance in millimeters (inches) 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.
2. Raceways approved for burial only where concrete encased shall require concrete envelope not less than 50 mm thick.
3. Lesser depths shall be permitted where cables and conductors rise for terminations or splices or where access is otherwise required.
4. Where one of the wiring method types listed in Columns 1–3 is used for one of the circuit types in Columns 4 and 5, the shallowest depth of burial shall be permitted.
5. 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 50 mm of concrete extending down to rock.


(h) Bushing.

A bushing, or terminal fitting, with an integral bushed opening shall be used at 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 permitted to be used in lieu of a bushing.

(i) Conductors of the Same Circuit.

All conductors of the same circuit and, where used, the grounded conductor and all equipment grounding conductors shall be installed in the same raceway or cable or shall be installed in close proximity in the same trench.

Exception No. 1: Conductors in parallel in raceways or cables shall be permitted, but each raceway or cable shall contain all conductors of the same circuit including grounding conductors.

Exception No. 2: Isolated phase, polarity, grounded conductor, and equipment grounding and bonding conductor installations shall be permitted in nonmetallic raceways or cables with a nonmetallic covering or nonmagnetic sheath in close proximity where conductors are paralleled as permitted in 3.10.1.4, and where the conditions of 3.0.1.20(b) are met.

(j) Ground 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 so as to prevent damage to the enclosed conductors or to equipment connected to the raceways.

FPN: This section recognizes “S” loops in underground direct burial to raceway transitions, expansion fittings in raceway risers to fixed equipment, and, generally, the provision of flexible connections to equipment subject to settlement or frost heaves.

(k) Directional Boring.

Cables or raceways installed using directional boring equipment shall be approved for the purpose.

3.0.1.6 Protection Against Corrosion and Deterioration.

Raceways, cable trays, cablebus, auxiliary gutters, cable armor, boxes, cable sheathing, cabinets, elbows, couplings, fittings, supports, and support hardware shall be of materials suitable for the environment in which they are to be installed.

(a) Ferrous Metal Equipment.

Ferrous metal raceways, cable trays, cablebus, auxiliary gutters, cable armor, boxes, cable sheathing, cabinets, metal elbows, couplings, nipples, fittings, supports, and support hardware shall be suitably protected against corrosion inside and outside (except threads at joints) by a coating of listed corrosion- resistant material. Where corrosion protection is necessary and the conduit is threaded in the field, the threads shall be coated with an approved electrically conductive, corrosion-resistant compound.

Exception: Stainless steel shall not be required to have protective coatings.

(1) Protected from Corrosion Solely by Enamel.

Where protected from corrosion solely by enamel, ferrous metal raceways, cable trays, cablebus, auxiliary gutters, cable armor, boxes, cable sheathing, cabinets, metal elbows, couplings, nipples, fittings, supports, and support hardware shall not be used outdoors or in wet locations as described in 3.0.1.6(d).

(2) Organic Coatings on Boxes or Cabinets.

Where boxes or cabinets have an approved system of organic coatings and are marked “Raintight,” “Rainproof,” or “Outdoor Type,” they shall be permitted outdoors.

(3) In Concrete or in Direct Contact with the Earth.

Ferrous metal raceways, cable armor, boxes, cable sheathing, cabinets, elbows, couplings, nipples, fittings, supports, and support hardware shall be permitted to be installed in concrete or in direct contact with the earth, or in areas subject to severe corrosive influences where made of material approved for the condition, or where provided with corrosion protection approved for the condition.

b) Non-Ferrous Metal Equipment.

Non-ferrous raceways, cable trays, cablebus, auxiliary gutters, cable armor, boxes, cable sheathing, cabinets, elbows, couplings, nipples, fittings, supports, and support hardware embedded or encased in concrete or in direct contact with the earth shall be provided with supplementary corrosion protection.

(c) Nonmetallic Equipment.

Nonmetallic raceways, cable trays, cablebus, auxiliary gutters, boxes, cables with a nonmetallic outer jacket and internal metal armor or jacket, cable sheathing, cabinets, elbows, couplings, nipples, fittings, supports, and support hardware shall be made of material approved for the condition and shall comply with (c)(1) and (c)(2) as applicable to the specific installation.

(1) Exposed to Sunlight.

Where exposed to sunlight, the materials shall be listed as sunlight resistant or shall be identified as sunlight resistant.

(2) Chemical Exposure.

Where subject to exposure to chemical solvents, vapors, splashing, or immersion, materials or coatings shall either be inherently resistant to chemicals based on its listing or be identified for the specific chemical reagent.

(d) Indoor Wet Locations.

In portions of dairy processing facilities, laundries, canneries, and other indoor wet locations, and in locations where walls are frequently washed or where there are surfaces of absorbent materials, such as damp paper or wood, the entire wiring system, where installed exposed, including all boxes, fittings, raceways, and cable used therewith, shall be mounted so that there is at least a 6 mm airspace between it and the wall or supporting surface.

Exception: Nonmetallic raceways, boxes, and fittings shall be permitted to be installed without the airspace on a concrete, masonry, tile, or similar surface.

FPN: In general, areas where acids and alkali chemicals are handled and stored may present such corrosive conditions, particularly when wet or damp. Severe corrosive conditions may also be present in portions of meatpacking plants, tanneries, glue houses, and some stables; in installations immediately adjacent to a seashore and swimming pool areas; in areas where chemical deicers are used; and in storage cellars or rooms for hides, casings, fertilizer, salt, and bulk chemicals.

3.0.1.7 Raceways Exposed to Different Temperatures.

(a) Sealing.

Where portions of a cable 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 filled with an approved material to prevent the circulation of warm air to a colder section of the raceway or sleeve. An explosionproof seal shall not be required for this purpose.

(b) Expansion Fittings.

Raceways shall be provided with expansion fittings where necessary to compensate for thermal expansion and contraction.

FPN: Table 3.52.2.35(a) provides the expansion information for polyvinyl chloride (PVC). A nominal number for steel conduit can be determined by multiplying the expansion length in this table by 0.20. The coefficient of expansion for steel electrical metallic tubing, intermediate metal conduit, and rigid conduit is 11.70 × 10-6 (0.0000117 mm per mm of conduit for each °C in temperature change) [6.50 × 10-6 (0.0000065 in. per inch of conduit for each °F in temperature change)]. 3.0.1.8 Installation of Conductors with Other Systems. Raceways or cable trays containing electric conductors shall not contain any pipe, tube, or equal for steam, water, air, gas, drainage, or any service other than electrical.

3.0.1.10 Electrical Continuity of Metal Raceways and Enclosures.

Metal raceways, cable armor, and other metal enclosures for conductors shall be metallically joined together into a continuous electric conductor and shall be connected to all boxes, fittings, and cabinets so as to provide effective electrical continuity. Unless specifically permitted elsewhere in this Code, raceways and cable assemblies shall be mechanically secured to boxes, fittings, cabinets, and other enclosures.

Exception No. 1: Short sections of raceways used to provide support or protection of cable assemblies from physical damage shall not be required to be made electrically continuous.

Exception No. 2: Equipment enclosures to be isolated, as permitted by 2.50.5.7(b), shall not be required to be metallically joined to the metal raceway.

3.0.1.11 Securing and Supporting.
(a) Secured in Place.

Raceways, cable assemblies, boxes, cabinets, and fittings shall be securely fastened in place. Support wires that do not provide secure support shall not be permitted as the sole support. Support wires and associated fittings that provide secure support and that are installed in addition to the ceiling grid support wires shall be permitted as the sole support. Where independent support wires are used, they shall be secured at both ends. Cables and raceways shall not be supported by ceiling grids.

======(1) Fire-Rated Assemblies. ======Wiring located within the cavity of a fire-rated floor–ceiling or roof–ceiling assembly shall not be secured to, or supported by, the ceiling assembly, including the ceiling support wires. An independent means of secure support shall be provided and shall be permitted to be attached to the assembly. Where independent support wires are used, they shall be distinguishable by color, tagging, or other effective means from those that are part of the fire-rated design.

Exception: The ceiling support system shall be permitted to support wiring and equipment that have been tested as part of the fire-rated assembly.

FPN: One method of determining fire rating is testing in accordance with NFPA 251-1999, Standard Methods of Tests of Fire Endurance of Building Construction and Materials.

(2) Non–Fire-Rated Assemblies.

Wiring located within the cavity of a non–fire-rated floor–ceiling or roof–ceiling assembly shall not be secured to, or supported by, the ceiling assembly, including the ceiling support wires. An independent means of secure support shall be provided.

Exception: The ceiling support system shall be permitted to support branch-circuit wiring and associated equipment where installed in accordance with the ceiling system manufacturer’s instructions.

(b) Raceways Used as Means of Support.

Raceways shall be used only as a means of support for other raceways, cables, or nonelectric equipment under any of the following conditions:

(1) Where the raceway or means of support is identified for the purpose
(2) Where the raceway contains power supply conductors for electrically controlled equipment and is used to support Class 2 circuit conductors or cables that are solely for the purpose of connection to the equipment control circuits
(3) Where the raceway is used to support boxes or conduit bodies in accordance with 3.14.2.9 or to support luminaires (fixtures) in accordance with 4.10.4.2(f)
(c) Cables Not Used as Means of Support.

Cable wiring methods shall not be used as a means of support for other cables, raceways, or nonelectrical equipment.

3.0.1.12 Mechanical Continuity — Raceways and Cables.

Metal or nonmetallic raceways, cable armors, and cable sheaths shall be continuous between cabinets, boxes, fittings, or other enclosures or outlets.

Exception: Short sections of raceways used to provide support or protection of cable assemblies from physical damage shall not be required to be mechanically continuous.

3.0.1.13 Mechanical and Electrical Continuity — Conductors. =

(a) General.

Conductors in raceways shall be continuous between outlets, boxes, devices, and so forth. There shall be no splice or tap within a raceway unless permitted by 3.0.1.15; 3.68.2.47(a); 3.76.2.47; 3.78.2.47; 3.84.2.47; 3.86.2.47; 3.88.2.47; or 3.90.1.6.

(b) Device Removal.

In multiwire branch circuits, the continuity of a grounded conductor shall not depend on device connections such as lampholders, receptacles, and so forth, where the removal of such devices would interrupt the continuity.

3.0.1.14 Length of Free Conductors at Outlets, Junctions, and Switch Points.

At least 150 mm of free conductor, measured from the point in the box where it emerges from its raceway or cable sheath, shall be left at each outlet, junction, and switch point for splices or the connection of luminaires (fixtures) or devices. Where the opening to an outlet, junction, or switch point is less than 200 mm in any dimension, each conductor shall be long enough to extend at least 75 mm outside the opening.

Exception: Conductors that are not spliced or terminated at the outlet, junction, or switch point shall not be required to comply with 3.0.1.14.

3.0.1.15 Boxes, Conduit Bodies, or Fittings — Where Required.

A box shall be installed at each outlet and switch point for concealed knob-and-tube wiring. Fittings and connectors shall be used only with the specific wiring methods for which they are designed and listed.

Where the wiring method is conduit, tubing, Type AC cable, Type MC cable, Type MI cable, nonmetallic-sheathed cable, or other cables, a box or conduit body shall be installed at each conductor splice point, outlet point, switch point, junction point, termination point, or pull point, unless otherwise permitted in 3.0.1.15(a) through (m).

(a) Wiring Methods with Interior Access.

A box or conduit body shall not be required for each splice, junction, switch, pull, termination, or outlet points in wiring methods with removable covers, such as wireways, multioutlet assemblies, auxiliary gutters, and surface raceways. The covers shall be accessible after installation.

(b) Equipment.

An integral junction box or wiring compartment as part of approved equipment shall be permitted in lieu of a box.

(c) Protection.

A box or conduit body shall not be required where cables enter or exit from conduit or tubing that is used to provide cable support or protection against physical damage. A fitting shall be provided on the end(s) of the conduit or tubing to protect the cable from abrasion.

(d) Type MI Cable.

A box or conduit body shall not be required where accessible fittings are used for straight-through splices in mineral-insulated metal-sheathed cable.

(e) Integral Enclosure.

A wiring device with integral enclosure identified for the use, having brackets that securely fasten the device to walls or ceilings of conventional on-site frame construction, for use with nonmetallic-sheathed cable, shall be permitted in lieu of a box or conduit body.

FPN: See 3.34.2.21(c); 5.45.1.10; 5.50.2.6(i); 5.51.4.8(e), Exception No. 1; and 5.52.4.9(e), Exception No. 1.

(f) Fitting.

A fitting identified for the use shall be permitted in lieu of a box or conduit body where conductors are not spliced or terminated within the fitting. The fitting shall be accessible after installation.

(g) Direct-Buried Conductors.

As permitted in 3.0.1.5(e), a box or conduit body shall not be required for splices and taps in direct-buried conductors and cables.

(h) Insulated Devices.

As permitted in 3.34.2.31(b), a box or conduit body shall not be required for insulated devices supplied by nonmetallic-sheathed cable.

(i) Enclosures.

A box or conduit body shall not be required where a splice, switch, terminal, or pull point is in a cabinet or cutout box, in an enclosure for a switch or overcurrent device as permitted in 3.12.1.8, in a motor controller as permitted in 4.30.1.10(a), or in a motor control center.

(j) Luminaires (Fixtures).

A box or conduit body shall not be required where a luminaire (fixture) is used as a raceway as permitted in 4.10.6.10 and 4.10.6.11.

(k) Embedded.

A box or conduit body shall not be required for splices where conductors are embedded as permitted in 4.24..5.7, 4.24.5.8(d), 4.26.3.3(b), 4.26.3.5(a), and 4.27.3.6(a).

(l) Manholes and Handhole Enclosures.

Where accessible only to licensed electrical practitioner or non licensed electrical practitioner under the supervision of a licensed electrical practitioner, a box or conduit body shall not be required for conductors in manholes or handhole enclosures, except where connecting to electrical equipment. The installation shall comply with the provisions of Part 1.10.5 for manholes, and 3.14.2.16 for handhole enclosures.

(m) Closed Loop.

A box shall not be required with a closed-loop power distribution system where a device identified and listed as suitable for installation without a box is used.

3.0.1.16 Raceway or Cable to Open or Concealed Wiring.

(a) Box or Fitting.

A box or terminal fitting having a separately bushed hole for each conductor shall be used wherever a change is made from conduit, electrical metallic tubing, electrical nonmetallic tubing, nonmetallic-sheathed cable, Type AC cable, Type MC cable, or mineral-insulated, metal-sheathed cable and surface raceway wiring to open wiring or to concealed knob-and-tube wiring. A fitting used for this purpose shall contain no taps or splices and shall not be used at luminaire (fixture) outlets.

(b) Bushing.

A bushing shall be permitted in lieu of a box or terminal where the conductors emerge from a raceway and enter or terminate at equipment, such as open switchboards, unenclosed control equipment, or similar equipment. The bushing shall be of the insulating type for other than lead-sheathed conductors.

3.0.1.17 Number and Size of Conductors in Raceway.

The number and size of conductors in any raceway shall not be more than will permit dissipation of the heat and ready installation or withdrawal of the conductors without damage to the conductors or to their insulation.

FPN: See the following sections of this Code: intermediate metal conduit, 3.42.2.13; rigid metal conduit, 3.44.2.13; flexible metal conduit, 3.48.2.13; liquidtight flexible metal conduit, 3.50.2.13; rigid nonmetallic conduit, 3.52.2.13; liquidtight nonmetallic flexible conduit, 3.56.2.13; electrical metallic tubing, 3.58.2.13; flexible metallic tubing, 3.60.2.13; electrical nonmetallic tubing, 3.62.2.13; cellular concrete floor raceways, 3.72.1.11; cellular metal floor raceways, 3.74.1.5; metal wireways, 3.76.2.13; nonmetallic wireways, 3.78.2.13; surface metal raceways, 3.86.2.13; surface nonmetallic raceways, 3.88.2.13; underfloor raceways, 3.90.1.5; fixture wire, 4.2.1.7; theaters, 5.20.1.6; signs, 6.0.2.2(c); elevators, 6.20.4.2; audio signal processing, amplification, and reproduction equipment, 6.40.2.3(a) and 6.40.2.4; Class 1, Class 2, and Class 3 circuits, Article 7.25; fire alarm circuits, Article 7.60; and optical fiber cables and raceways, Article 7.70.

3.0.1.18 Raceway Installations.

(a) Complete Runs.

Raceways, other than busways or exposed raceways having hinged or removable covers, shall be installed complete between outlet, junction, or splicing points prior to the installation of conductors. Where required to facilitate the installation of utilization equipment, the raceway shall be permitted to be initially installed without a terminating connection at the equipment. Prewired raceway assemblies shall be permitted only where specifically permitted in this Code for the applicable wiring method.

Exception: Short sections of raceways used to contain conductors or cable assemblies for protection from physical damage shall not be required to be installed complete between outlet, junction, or splicing points.

(b) Welding.

Metal raceways shall not be supported, terminated, or connected by welding to the raceway unless specifically designed to be or otherwise specifically permitted to be in this Code.

3.0.1.19 Supporting Conductors in Vertical Raceways.

(a) Spacing Intervals — Maximum.

Conductors in vertical raceways shall be supported if the vertical rise exceeds the values in Table 3.0.1.19(a). One cable support shall be provided at the top of the vertical raceway or as close to the top as practical. Intermediate supports shall be provided as necessary to limit supported conductor lengths to not greater than those values specified in Table 3.0.1.19(a). Exception: Steel wire armor cable shall be supported at the top of the riser with a cable support that clamps the steel wire armor. A safety device shall be permitted at the lower end of the riser to hold the cable in the event there is slippage of the cable in the wire-armored cable support. Additional wedge-type supports shall be permitted to relieve the strain on the equipment terminals caused by expansion of the cable under load.

(b) Support Methods.

One of the following methods of support shall be used.

(1) By clamping devices constructed of or employing insulating wedges inserted in the ends of the raceways. Where clamping of insulation does not adequately support the cable, the conductor also shall be clamped.
(2) By inserting boxes at the required intervals in which insulating supports are installed and secured in a satisfactory manner to withstand the weight of the conductors attached thereto, the boxes being provided with covers.
(3) In junction boxes, by deflecting the cables not less than 90 degrees and carrying them horizontally to a distance not less than twice the diameter of the cable, the cables being carried on two or more insulating supports and additionally secured thereto by tie wires if desired. Where this method is used, cables shall be supported at intervals not greater than 20 percent of those mentioned in the preceding tabulation.
(4) By a method of equal effectiveness.


Table 3.0.1.19(a) Spacings for Conductor Supports
Size of Wire mm2 (mm dia.) Support of Conductors in Vertical Raceways Conductors
Aluminum or Copper-Clad Aluminum (m) Copper (m)
0.75(1.0) through 8.0(3.2) Not greater than 30 30
14 through 38 Not greater than 60 30
60 through 100 Not greater than 55 25
Over 100 through 175 Not greater than 40 18
Over 175 through 250 Not greater than 35 15
Over 250 through 400 Not greater than 30 12
Over 400 Not greater than 25 11


3.0.1.20 Induced Currents in Metal Enclosures or Metal Raceways.

(a) Conductors Grouped Together.

Where conductors carrying alternating current are installed in metal enclosures or metal raceways, they shall be arranged so as to avoid heating the surrounding metal by induction. To accomplish this, all phase conductors and, where used, the grounded conductor and all equipment grounding conductors shall be grouped together.

Exception No. 1: Equipment grounding conductors for certain existing installations shall be permitted to be installed separate from their associated circuit conductors where run in accordance with the provisions of 2.50.7.1(c).

Exception No. 2: A single conductor shall be permitted to be installed in a ferromagnetic enclosure and used for skin-effect heating in accordance with the provisions of 4.26.5.3 and 4.27.6.3.

(b) Individual Conductors.

Where a single conductor carrying alternating current passes through metal with magnetic properties, the inductive effect shall be minimized by (1) cutting slots in the metal between the individual holes through which the individual conductors pass or (2) passing all the conductors in the circuit through an insulating wall sufficiently large for all of the conductors of the circuit.

Exception: In the case of circuits supplying vacuum or electric- discharge lighting systems or signs or X-ray apparatus, the currents carried by the conductors are so small that the inductive heating effect can be ignored where these conductors are placed in metal enclosures or pass through metal.

FPN: Because aluminum is not a magnetic metal, there will be no heating due to hysteresis; however, induced currents will be present. They will not be of sufficient magnitude to require grouping of conductors or special treatment in passing conductors through aluminum wall sections.


3.0.1.21 Spread of Fire or Products of Combustion.

Electrical installations in hollow spaces, vertical shafts, and ventilation or air- handling ducts shall be made so that the possible spread of fire or products of combustion will not be substantially increased. Openings around electrical penetrations through fire-resistant–rated walls, partitions, floors, or ceilings shall be firestopped using approved methods to maintain the fire resistance rating.

FPN: Directories of electrical construction materials published by qualified testing laboratories contain many listing installation restrictions necessary to maintain the fire-resistive rating of assemblies where penetrations or openings are made. Building codes also contain restrictions on membrane penetrations on opposite sides of a fire-resistance–rated wall assembly. An example is the 600 mm minimum horizontal separation that usually applies between boxes installed on opposite sides of the wall. Assistance in complying with 3.0.1.21 can be found in building codes, fire resistance directories, and product listings.

3.0.1.22 Wiring in Ducts, Plenums, and Other Air-Handling Spaces.

The provisions of this section apply to the installation and uses of electric wiring and equipment in ducts, plenums, and other air-handling spaces.

FPN: See Part 4.24.6, for duct heaters.

(a) Ducts for Dust, Loose Stock, or Vapor Removal.

No wiring systems of any type shall be installed in ducts used to transport dust, loose stock, or flammable vapors. No wiring system of any type shall be installed in any duct, or shaft containing only such ducts, used for vapor removal or for ventilation of commercial-type cooking equipment.

(b) Ducts or Plenums Used for Environmental Air.

Only wiring methods consisting of Type MI cable, Type MC cable employing a smooth or corrugated impervious metal sheath without an overall nonmetallic covering, electrical metallic tubing, flexible metallic tubing, intermediate metal conduit, or rigid metal conduit without an overall nonmetallic covering shall be installed in ducts or plenums specifically fabricated to transport environmental air. Flexible metal conduit shall be permitted, in lengths not to exceed 1 200 mm, to connect physically adjustable equipment and devices permitted to be in these ducts and plenum chambers. The connectors used with flexible metal conduit shall effectively close any openings in the connection. Equipment and devices shall be permitted within such ducts or plenum chambers only if necessary for their direct action upon, or sensing of, the contained air. Where equipment or devices are installed and illumination is necessary to facilitate maintenance and repair, enclosed gasketed-type luminaires (fixtures) shall be permitted.

(c) Other Space Used for Environmental Air.

This section applies to space used for environmental air-handling purposes other than ducts and plenums as specified in 3.0.1.22(a) and (b). It does not include habitable rooms or areas of buildings, the prime purpose of which is not air handling.

FPN: The space over a hung ceiling used for environmental air-handling purposes is an example of the type of other space to which this section applies.

Exception: This section shall not apply to the joist or stud spaces of dwelling units where the wiring passes through such spaces perpendicular to the long dimension of such spaces.

(1) Wiring Methods.

The wiring methods for such other space shall be limited to totally enclosed, nonventilated, insulated busway having no provisions for plug-in connections, Type MI cable, Type MC cable without an overall nonmetallic covering, Type AC cable, or other factory-assembled multiconductor control or power cable that is specifically listed for the use, or listed prefabricated cable assemblies of metallic manufactured wiring systems without nonmetallic sheath. Other types of cables and conductors shall be installed in electrical metallic tubing, flexible metallic tubing, intermediate metal conduit, rigid metal conduit without an overall nonmetallic covering, flexible metal conduit, or, where accessible, surface metal raceway or metal wireway with metal covers or solid bottom metal cable tray with solid metal covers.

(2) Equipment.

Electrical equipment with a metal enclosure, or with a nonmetallic enclosure listed for the use and having adequate fire-resistant and low-smoke-producing characteristics, and associated wiring material suitable for the ambient temperature shall be permitted to be installed in such other space unless prohibited elsewhere in this Code.

Exception: Integral fan systems shall be permitted where specifically identified for such use.

(d) Information Technology Equipment.

Electric wiring in air- handling areas beneath raised floors for information technology equipment shall be permitted in accordance with Article 6.45.

3.0.1.23 Panels Designed to Allow Access.

Cables, raceways, and equipment installed behind panels designed to allow access, including suspended ceiling panels, shall be arranged and secured so as to allow the removal of panels and access to the equipment.

3.0.2 Requirements for Over 600 Volts, Nominal

3.0.2.1 Covers Required.

Suitable covers shall be installed on all boxes, fittings, and similar enclosures to prevent accidental contact with energized parts or physical damage to parts or insulation.

3.0.2.2 Conductors of Different Systems. See 3.0.1.3(c)(2).

3.0.2.4 Conductor Bending Radius.

The conductor shall not be bent to a radius less than 8 times the overall diameter for nonshielded conductors or 12 times the overall diameter for shielded or lead- covered conductors during or after installation. For multiconductor or multiplexed single conductor cables having individually shielded conductors, the minimum bending radius is 12 times the diameter of the individually shielded conductors or 7 times the overall diameter, whichever is greater.

3.0.2.5 Protection Against Induction Heating.

Metallic raceways and associated conductors shall be arranged so as to avoid heating of the raceway in accordance with the applicable provisions of 3.0.1.20.

3.0.2.7 Aboveground Wiring Methods.

Aboveground conductors shall be installed in rigid metal conduit, in intermediate metal conduit, in electrical metallic tubing, in rigid nonmetallic conduit, in cable trays, as busways, as cablebus, in other identified raceways, or as exposed runs of metal-clad cable suitable for the use and purpose. In locations accessible to licensed electrical practitioner or non licensed electrical practitioner under the supervision of a licensed electrical practitioner only, exposed runs of Type MV cables, bare conductors, and bare busbars shall also be permitted. Busbars shall be permitted to be either copper or aluminum.

3.0.2.9 Braid-Covered Insulated Conductors — Exposed Installation.

Exposed runs of braid-covered insulated conductors shall have a flame-retardant braid. If the conductors used do not have this protection, a flame-retardant saturant shall be applied to the braid covering after installation. This treated braid covering shall be stripped back a safe distance at conductor terminals, according to the operating voltage. Where practicable, this distance shall not be less than 25 mm for each kilovolt of the conductor-to-ground voltage of the circuit.

3.0.2.10 Insulation Shielding.

Metallic and semiconducting insulation shielding components of shielded cables shall be removed for a distance dependent on the circuit voltage and insulation. Stress reduction means shall be provided at all terminations of factory- applied shielding.

Metallic shielding components such as tapes, wires, or braids, or combinations thereof, and their associated conducting or semiconducting components shall be grounded.

3.0.2.12 Moisture or Mechanical Protection for Metal-Sheathed Cables.

Where cable conductors emerge from a metal sheath and where protection against moisture or physical damage is necessary, the insulation of the conductors shall be protected by a cable sheath terminating device.

3.0.2.20 Underground Installations.

(a) General.

Underground conductors shall be identified for the voltage and conditions under which they are installed. Direct burial cables shall comply with the provisions of 3.10.1.7. Underground cables shall be installed in accordance with 3.0.2.20(a)(1) or (a)(2), and the installation shall meet the depth requirements of Table 3.0.2.20.

(1) Shielded Cables and Nonshielded Cables in Metal-Sheathed Cable Assemblies.

Underground cables, including nonshielded, Type MC and moisture-impervious metal sheath cables, shall have those sheaths grounded through an effective grounding path meeting the requirements of 2.50.1.4(a)(5) or (b)(4). They shall be direct buried or installed in raceways identified for the use.

(2) Other Nonshielded Cables.

Other nonshielded cables not covered in 3.0.2.20(a)(1) shall be installed in rigid metal conduit, intermediate metal conduit, or rigid nonmetallic conduit encased in not less than 75 mm of concrete.

Table 3.0.2.20 Minimum Cover1 Requirements
Circuit Voltage General Conditions (not otherwise specified) Special Conditions (use if applicable)
(1)
Direct-Buried Cables
(mm)
(2)
Rigid Nonmetallic Conduit2
(mm)
(3)
Rigid Metal Conduit and Intermediate Metal Conduit
(mm)
(4)
Raceways under buildings or exterior concrete slabs, 100mm minimum thickness3
(mm)
(5)
Cables in airport runways or adjacent areas where trespass is prohibited
(mm)
(6)
Areas subject to vehicular traffic, such as thoroughfares and commercial parking areas
(mm)
Over 600 V through 22 kV 760 460 150 100 450 600
Over 22 kV through 40 kV 900 600 150 100 450 600
Over 40 kV 1000 760 150 100 450 600
Notes:
1. Lesser depths shall be permitted where cables and conductors rise for terminations or splices or where access is otherwise required.
2. Where solid rock prevents compliance with the cover depths specified in this table, the wiring shall be installed in a metal or nonmetallic raceway permitted for direct burial. The raceways shall be covered by a minimum of 50 mm of concrete extending down to rock.
1 Cover is defined as the shortest distance in 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.
2 Listed by a qualified testing agency as suitable for direct burial without encasement. All other nonmetallic systems shall require 50 mm of concrete or equivalent above conduit in addition to the table depth.
3 The slab shall extend a minimum of 150 mm beyond the underground installation, and a warning ribbon or other effective means suitable for the conditions shall be placed above the underground installation.


(b) Protection from Damage.

Conductors emerging from the ground shall be enclosed in listed raceways. Raceways installed on poles shall be of rigid metal conduit, intermediate metal conduit, PVC Schedule 80, or equivalent, extending from the minimum cover depth specified in Table 3.0.2.20 to a point 2 400 mm above finished grade. Conductors entering a building shall be protected by an approved enclosure or raceway from the minimum cover depth to the point of entrance. Where direct-buried conductors, raceways, or cables are subject to movement by settlement or frost, they shall be installed to prevent damage to the enclosed conductors or to the equipment connected to the raceways. Metallic enclosures shall be grounded.

(c) Splices.

Direct burial cables shall be permitted to be spliced or tapped without the use of splice boxes, provided they are installed using materials suitable for the application. The taps and splices shall be watertight and protected from mechanical damage. Where cables are shielded, the shielding shall be continuous across the splice or tap. Exception: At splices of an engineered cabling system, metallic shields of direct-buried single-conductor cables with maintained spacing between phases shall be permitted to be interrupted and overlapped. Where shields are interrupted and overlapped, each shield section shall be grounded at one point.

(d) Backfill.

Backfill containing large rocks, paving materials, cinders, large or sharply angular substances, or corrosive materials shall not be placed in an excavation where materials can damage or contribute to the corrosion of raceways, cables, or other substructures or where it may prevent adequate compaction of fill. Protection in the form of granular or selected material or suitable sleeves shall be provided to prevent physical damage to the raceway or cable.

(e) Raceway Seal.

Where a raceway enters from an underground system, the end within the building shall be sealed with an identified compound so as to prevent the entrance of moisture or gases, or it shall be so arranged to prevent moisture from contacting live parts.


Other Pages in this Category: Chapter 3. Wiring Methods and Materials

References