5.7 Cable Trays, Wireways, Busways, Gutters and Surface Raceways

Alaska Journeyman Electrician Study Guide Exam

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1 Chapter 1: Alaska Certificates of Fitness, Law & Exam Logistics

1.1 The Alaska Certificate of Fitness System 1.2 Journeyman Eligibility: 8,000 Hours and How Alaska Counts Them 1.3 Trainee, Residential Wireman, Lineman, Provisional & Reciprocal Certificates 1.4 The Journeyman Examination: Format, Scheduling, Open-Book Rules & Retakes 1.5 Adopted Codes, Fees, Renewal, Inspection & Enforcement

2 Chapter 2: Using the 2020 NEC

2.1 Article 90: Purpose, Scope, Arrangement & Enforcement 2.2 Navigating the Code Book: Structure, Index & Tabbing Strategy 2.3 Article 100 Definitions You Must Know Cold 2.4 Electrical Theory for the Exam: Ohm's Law, Power & Three-Phase

3 Chapter 3: General Requirements — Article 110

3.1 Approval, Listing, Interrupting Rating & Terminations 3.2 Temperature Limitations of Terminations — 110.14(C) 3.3 Working Space, Access, Egress & Illumination — 110.26(A) through (D) 3.4 Dedicated Equipment Space, Guarding & Over-1000-Volt Installations

4 Chapter 4: Conductors and Ampacity — Article 310

4.1 Conductor Types, Insulation Markings & Table 310.16 4.2 Ambient Temperature Correction and Alaska's Cold 4.3 Adjustment for More Than Three Current-Carrying Conductors 4.4 Putting It Together: Full Conductor-Sizing Problems 4.5 Parallel Conductors, Dwelling Service Sizing & Conditions of Use

5 Chapter 5: Wiring Methods and Materials — NEC Chapter 3

5.1 Article 300 General Requirements and Underground Cover 5.2 Thermal Movement: Expansion Fittings and Table 352.44 5.3 Boxes and Enclosures: Box Fill and Pull Box Sizing 5.4 Cable Assemblies: NM, MC, AC, SE, UF and TC 5.5 Raceways: RMC, IMC, EMT, FMC, LFMC, PVC and ENT 5.6 Conduit Fill: Chapter 9 Tables and Annex C 5.7 Cable Trays, Wireways, Busways, Gutters and Surface Raceways

6 Chapter 6: Branch Circuits and Feeders

6.1 Branch-Circuit Ratings, Conductor Sizing & Multiwire Circuits 6.2 Required Outlets and Receptacle Spacing in Dwellings 6.3 GFCI Protection — Article 210.8 6.4 AFCI Protection and Receptacle Requirements 6.5 Feeders and Outside Branch Circuits — Articles 215 and 225 6.6 Grounded Conductor Identification, Switches & Panelboards

7 Chapter 7: Overcurrent Protection — Articles 240 and 242

7.1 Article 240 Fundamentals: Ratings, Locations & Conductor Protection 7.2 Feeder Tap Rules — 240.21(B) 7.3 Transformer Secondary Conductors — 240.21(C) 7.4 Fuses, Circuit Breakers, Series Ratings & Article 242 Surge Protection

8 Chapter 8: Services and Load Calculations

8.1 Service Conductors, Clearances and Service Equipment 8.2 Service Disconnects, the 2020 Rule Change, SPDs and Service GFPE 8.3 Article 220 Part II: General Lighting, Receptacles and Demand Factors 8.4 The Standard Dwelling Calculation — Article 220 Part III 8.5 Optional Dwelling and Multifamily Calculations 8.6 Commercial and Industrial Load Calculations 8.7 Neutral Load Calculations and Harmonics — 220.61

9 Chapter 9: Grounding and Bonding — Article 250

9.1 System Grounding, 250.24 and the Main Bonding Jumper 9.2 The Grounding Electrode System — 250.50 through 250.53 9.3 Grounding Electrode Conductor Sizing and Installation 9.4 Bonding: Services, Metal Piping, Structural Metal and Other Systems 9.5 Equipment Grounding Conductors: Types, Sizing and Continuity 9.6 Separately Derived Systems and Separate Buildings 9.7 Ground-Fault Protection of Equipment and Grounding of Specific Equipment

10 Chapter 10: Equipment for General Use — NEC Chapter 4

10.1 Flexible Cords, Cables and Fixture Wires 10.2 Switches, Receptacles and Industrial Control Panels 10.3 Luminaires, Lampholders and Recessed Installations 10.4 Appliances and Fixed Electric Space Heating 10.5 Deicing, Snow Melting, Pipeline and Vessel Heating 10.6 Motors Part I: Full-Load Current, Conductors and Overload Protection 10.7 Motors Part II: Short-Circuit Protection, Controllers, Disconnects and HVAC

11 Chapter 11: Transformers, Generators and Special Occupancies

11.1 Transformers — Article 450 11.2 Generators, Storage Batteries and Energy Storage Systems 11.3 Hazardous (Classified) Locations — Articles 500 through 506 11.4 Garages, Hangars, Fuel Dispensing, Bulk Storage and Spray Application 11.5 Health Care Facilities — Article 517 11.6 Agricultural Buildings, Manufactured Homes, RV Parks and Marinas 11.7 Assembly, Theaters, Carnivals, Temporary Installations and Pools

12 Chapter 12: Special Equipment, Special Conditions and Exam Strategy

12.1 Signs, Cranes, Elevators, Electric Vehicle Charging and Welders 12.2 Solar Photovoltaic, Interconnection and Stand-Alone Systems 12.3 Wind Electric Systems and Fire Pumps 12.4 Emergency, Legally Required Standby, Optional Standby and COPS 12.5 Class 1, 2 and 3 Circuits, Fire Alarm, Optical Fiber and Communications 12.6 Cold-Climate Practice in Alaska: Code Basis and Engineering Judgment 12.7 Exam-Day Strategy: Navigation, Calculation Workflow and Time Management

5.7 Cable Trays, Wireways, Busways, Gutters and Surface Raceways

Key Takeaways Explain This Topic AI

NEC 376.22(A) limits metal wireway conductor fill to 20 percent of the interior cross-sectional area, and 376.22(B) applies the 310.15(C)(1) adjustment factors only where more than 30 current-carrying conductors are installed.

NEC 366.22 limits metal auxiliary gutter fill to 20 percent, and 366.23 limits the ampere rating of bare conductors in an auxiliary gutter to 1000 amperes per square inch of cross section.

NEC 392.22 governs cable tray fill and depends on cable type and tray width, with 392.80 providing ampacity rules including a 75 percent factor for multiconductor cables in a covered tray longer than 6 feet.

NEC 368.17(B) permits a busway to be tapped by a smaller busway without additional overcurrent protection where the smaller busway has an ampacity at least one third of the protecting device and does not exceed 50 feet in length.

NEC 386.56 and 388.56 permit splices and taps in surface metal and surface nonmetallic raceways only where the raceway has a removable cover accessible after installation, with splices and taps not filling more than 75 percent of the area at that point.

Last updated: August 2026

Metal Wireways — Article 376

A wireway is a sheet-metal trough with a hinged or removable cover, used for housing and protecting conductors and cable where the conductors are laid in place after the wireway is installed .

376.12 Uses Not Permitted. Where subject to severe physical damage or corrosive vapor, and in any hazardous (classified) location except as permitted by other articles.

376.22 Number of Conductors and Ampacity.

(A) Cross-Sectional Areas of Wireway. The sum of the cross-sectional areas of all contained conductors at any cross section shall not exceed 20 percent of the interior cross-sectional area of the wireway.

(B) Adjustment Factors. The adjustment factors in 310.15(C)(1) shall be applied only where the number of current-carrying conductors, including neutrals classified as current-carrying under 310.15(E), exceeds 30 . Conductors for signaling circuits or controller conductors between a motor and its starter, used only for starting duty, shall not be considered current-carrying.

The 30-conductor threshold is a large relaxation compared with the 3-conductor threshold for raceways, and it is a common exam item.

376.23(A) Deflected Insulated Conductors. Where insulated conductors are deflected within a wireway, either at the ends or where conduits enter or leave the wireway, or where the direction of the wireway is deflected more than 30 degrees, dimensions corresponding to 312.6(A) shall apply.

376.56 Splices, Taps, and Power Distribution Blocks. Splices and taps are permitted within a wireway provided they are accessible . The conductors, including splices and taps, shall not fill the wireway to more than 75 percent of its area at that point.

376.30 Securing and Supporting. Wireways shall be supported where run horizontally at each end and at intervals not exceeding 5 feet , or for listed wireways at intervals not exceeding 10 feet . Vertical runs shall be securely supported at intervals not exceeding 15 feet with not more than one joint between supports.

Nonmetallic Wireways (Article 378) have parallel rules with the same 20 percent fill, but their adjustment threshold and expansion-fitting requirements differ — 378.30 requires support at intervals not exceeding 3 feet unless listed for other spacing, and 378.44 requires expansion fittings where the expected length change exceeds 0.25 inch.

Auxiliary Gutters — Article 366

An auxiliary gutter supplements wiring spaces at meter centers, distribution centers, switchboards, and similar points . It looks like a wireway but has a different purpose and a length restriction: 366.12(1) prohibits an auxiliary gutter from containing conductors extending more than 30 feet (9 m) beyond the equipment it supplements, with an exception for elevators.

366.22(A) Sheet Metal Auxiliary Gutters. Conductors shall not fill more than 20 percent of the interior cross-sectional area. Where the number of current-carrying conductors exceeds 30 , the adjustment factors of 310.15(C)(1) apply. Conductors for signaling circuits or controller conductors between a motor and its starter used only for starting duty are not counted.

366.23(A) Ampacity of Bare Conductors. Where bare conductors are installed in an auxiliary gutter, the current shall not exceed 1000 amperes per square inch of cross section of the conductor.

366.30 requires gutters to be supported throughout their length at intervals not exceeding 5 feet for sheet metal, or per the listing for nonmetallic.

Cable Trays — Article 392

A cable tray is a support system , not a raceway. This distinction drives several rules.

392.10 Uses Permitted. Cable tray may support MI, MC, MV, AC, NM, TC, ITC, PLTC, optical fiber cables, and other listed assemblies. In industrial establishments only where conditions of maintenance and supervision ensure that only qualified persons service the installation, single conductors 1/0 AWG and larger may be installed in ladder, ventilated trough, or ventilated channel-type cable tray.

392.12 Uses Not Permitted. In hoistways; where subject to severe physical damage.

392.18(A) Complete System. Cable trays shall be installed as a complete system, with field bends and modifications made so the electrical continuity and cable support of the system are maintained.

392.20 Cable and Conductor Installation. (C) Multiconductor cables rated 2000 V or less shall be permitted to be installed in the same cable tray. (D) Cables rated over 2000 V shall not be installed in the same tray with cables rated 2000 V or less unless separated by a solid fixed barrier or the higher-voltage cables are Type MC.

392.22 Number of Multiconductor Cables Rated 2000 Volts or Less in Cable Trays. The permitted fill depends on the tray type and whether the cables are all 4/0 or larger, all smaller than 4/0, or mixed, with formulas given in 392.22(A)(1) through (A)(4). Ladder and ventilated trough trays are permitted a greater fill than solid-bottom trays.

392.30(A) Cable Trays as Support. Cable trays shall be supported at intervals in accordance with the installation instructions.

392.60(B) Cable Tray as an Equipment Grounding Conductor. Metallic cable trays shall be permitted to be used as equipment grounding conductors only in industrial establishments where qualified persons service the installation, the tray sections and fittings are identified for grounding purposes, and the minimum cross-sectional area of the tray complies with Table 392.60(A).

392.80 Ampacity of Conductors. For multiconductor cables in a tray, the ampacity is generally per 310.14 for cables with three or fewer current-carrying conductors, and adjustment factors apply as specified. Where multiconductor cables are installed in a cable tray with a solid cover more than 6 feet in length , the ampacity shall not exceed 95 percent of the allowable ampacities in the applicable table — and for single conductors, 75 percent applies to covered trays exceeding 6 feet. Read 392.80 carefully; the percentages differ between the multiconductor and single-conductor subsections.

Busways — Article 368

A busway is a grounded metal enclosure containing factory-mounted bare or insulated conductors, usually copper or aluminum bars, rods, or tubes.

368.10 Uses Permitted. Busways shall be permitted to be installed where they are located in the open and visible , except as permitted in 368.10(C) for behind panels where access is provided and specified conditions are met.

368.12 Uses Not Permitted. Where subject to severe physical damage or corrosive vapors; in hoistways; in any hazardous location unless specifically approved; outdoors or in wet or damp locations unless identified for such use; where exposed to corrosive vapors.

368.17(A) Rating of Overcurrent Protection — Feeders. A busway shall be protected against overcurrent in accordance with the allowable current rating of the busway.

368.17(B) Reduction in Ampacity Size of Busway. Overcurrent protection shall be required where busways are reduced in ampacity. Exception: For industrial establishments only, omission of overcurrent protection is permitted at points where busways are reduced in ampacity, provided the length of the busway having the smaller ampacity does not exceed 50 feet (15 m) and has an ampacity at least equal to one third the rating or setting of the overcurrent device next back on the line, and provided such busway is free from contact with combustible material.

368.17(C) Feeder or Branch Circuits. Where a busway is used as a feeder, devices or plug-in connections for tapping off feeder or branch circuits from the busway shall contain the overcurrent devices required for the protection of the feeder or branch circuits. An exception permits omission where the tapped conductors are not more than 50 feet long, are enclosed in metal raceway, and are of adequate ampacity.

368.30 Support. Busways shall be securely supported at intervals not exceeding 5 feet (1.5 m) unless otherwise designed and marked.

Surface Raceways — Articles 386 and 388

Surface Metal Raceway (386) and Surface Nonmetallic Raceway (388) are used for exposed work in dry locations.

386.12 / 388.12 Uses Not Permitted. Where subject to severe physical damage unless approved for that purpose; where the voltage is 300 volts or more between conductors unless the metal has a thickness of not less than 1.02 mm (0.040 in.); where subject to corrosive vapors; in hoistways; in hazardous locations except as permitted. Surface nonmetallic raceway is additionally prohibited where subject to ambient temperatures exceeding those for which it is listed.

386.22 / 388.22 Number of Conductors. The number of conductors shall not be greater than the number for which the raceway is designed , and the cross-sectional area shall not exceed that for which the raceway is listed. The 310.15(C)(1) adjustment factors do not apply where all of the following conditions are met: the cross-sectional area of the raceway exceeds 4 square inches, the current-carrying conductors do not exceed 30 in number, and the sum of the cross-sectional areas of all conductors does not exceed 20 percent of the interior cross-sectional area of the raceway.

386.56 / 388.56 Splices and Taps. Splices and taps shall be permitted in surface raceways having a removable cover that is accessible after installation . The conductors, including splices and taps, shall not fill the raceway to more than 75 percent of its area at that point.