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Chapter 3 Wiring Methods and Materials | 390.15(D) | In office occupancies, approved metal flat-top raceways, if not over 100 mm (4 in.) in width, shall be permitted to be laid flush with the concrete floor surface, provided they are covered with substantial linoleum that is not less than 1.6 mm (1/16 in.) thick or with equivalent floor covering. Where more than one and not more than three single raceways are each installed flush with the concrete, they shall be contiguous with each other and joined to form a rigid assembly. [390.15(D)](https://2023.antflix.net#390.15(D)) | https://2023.antflix.net#390.15(D) |
Chapter 3 Wiring Methods and Materials | 390.20 | No conductor larger than that for which the raceway is designed shall be installed in underfloor raceways. [390.20](https://2023.antflix.net#390.20) | https://2023.antflix.net#390.20 |
Chapter 3 Wiring Methods and Materials | 390.22 | The combined cross-sectional area of all conductors or cables shall not exceed 40 percent of the interior cross-sectional area of the raceway. [390.22](https://2023.antflix.net#390.22) | https://2023.antflix.net#390.22 |
Chapter 3 Wiring Methods and Materials | 390.23 | The ampacity adjustment factors in 310.15(C) shall apply to conductors installed in underfloor raceways. [390.23](https://2023.antflix.net#390.23) | https://2023.antflix.net#390.23 |
Chapter 3 Wiring Methods and Materials | 390.56 | Splices and taps shall be made only in junction boxes. For the purposes of this section, so-called loop wiring (continuous, unbroken conductor connecting the individual outlets) shall not be considered to be a splice or tap. Exception: Splices and taps shall be permitted in trench-type flush raceway having a removable cover that is accessible after installation. The conductors, including splices and taps, shall not fill more than 75 percent of the raceway area at that point. [390.56](https://2023.antflix.net#390.56) | https://2023.antflix.net#390.56 |
Chapter 3 Wiring Methods and Materials | 390.57 | When an outlet is abandoned, discontinued, or removed, the sections of circuit conductors supplying the outlet shall be removed from the raceway. No splices or reinsulated conductors, such as would be the case with abandoned outlets on loop wiring, shall be allowed in raceways. [390.57](https://2023.antflix.net#390.57) | https://2023.antflix.net#390.57 |
Chapter 3 Wiring Methods and Materials | 390.70 | Underfloor raceways shall be laid so that a straight line from the center of one junction box to the center of the next junction box coincides with the centerline of the raceway system. Raceways shall be firmly held in place to prevent disturbing this alignment during construction. [390.70](https://2023.antflix.net#390.70) | https://2023.antflix.net#390.70 |
Chapter 3 Wiring Methods and Materials | 390.71 | A suitable marker shall be installed at or near each end of each straight run of raceways to locate the last insert. [390.71](https://2023.antflix.net#390.71) | https://2023.antflix.net#390.71 |
Chapter 3 Wiring Methods and Materials | 390.73 | Dead ends of raceways shall be closed. [390.73](https://2023.antflix.net#390.73) | https://2023.antflix.net#390.73 |
Chapter 3 Wiring Methods and Materials | 390.74 | Junction boxes shall be leveled to the floor grade and sealed to prevent the free entrance of water or concrete. Junction boxes used with metal raceways shall be metal and shall be electrically continuous with the raceways. [390.74](https://2023.antflix.net#390.74) | https://2023.antflix.net#390.74 |
Chapter 3 Wiring Methods and Materials | 390.75 | Inserts shall be leveled and sealed to prevent the entrance of concrete. Inserts used with metal raceways shall be metal and shall be electrically continuous with the raceway. Inserts set in or on fiber raceways before the floor is laid shall be mechanically secured to the raceway. Inserts set in fiber raceways after the floor is laid shall be screwed into the raceway. When cutting through the raceway wall and setting inserts, chips and other dirt shall not be allowed to remain in the raceway, and tools shall be used that are designed so as to prevent the tool from entering the raceway and damaging conductors that may be in place. [390.75](https://2023.antflix.net#390.75) | https://2023.antflix.net#390.75 |
Chapter 3 Wiring Methods and Materials | 390.76 | Connections from underfloor raceways to distribution centers and wall outlets shall be made by approved fittings or by any of the wiring methods in Chapter 3, where installed in accordance with the respective articles. [390.76](https://2023.antflix.net#390.76) | https://2023.antflix.net#390.76 |
Chapter 3 Wiring Methods and Materials | 392.1 | This article covers cable tray systems, including ladder, ventilated trough, ventilated channel, solid bottom, and other similar structures. Informational Note: See ANSI/NEMA-VE 1-2017, Metal Cable Tray Systems, and NECA/NEMA 105-2015, Standard for Installing Metal Cable Tray Systems, for further information on cable trays. [392.1](https://2023.antflix.net#392.1) | https://2023.antflix.net#392.1 |
Chapter 3 Wiring Methods and Materials | 392.10 | Cable tray shall be permitted to be used as a support system for wiring methods containing service conductors, feeders, branch circuits, communications circuits, control circuits, and signaling circuits. Single insulated cables and single insulated conductors shall be permitted in cable tray only when installed in accordance with 392.10(B)(1). Cable tray installations shall not be limited to industrial establishments. Where exposed to direct rays of the sun, insulated conductors and jacketed cables shall be identified as being sunlight resistant. Cable trays and their associated fittings shall be identified for the intended use. [392.10](https://2023.antflix.net#392.10) | https://2023.antflix.net#392.10 |
Chapter 3 Wiring Methods and Materials | 392.10(A) | The wiring methods in Table 392.10(A) shall be permitted to be installed in cable tray systems under the conditions described in their respective articles and sections.
Table 392.10(A) Wiring Methods
Wiring Method
Article
Armored cable: Type AC
320
CATV cables
800 and 820
Class 2 and Class 3 cables
722 and 725
Communications cables
800 and 805
Communications raceways
800
Electrical metallic tubing: EMT
358
Electrical nonmetallic tubing: ENT
362
Fire alarm cables
722 and 760
Flexible metal conduit: FMC
348
Flexible metallic tubing: FMT
360
Instrumentation tray cable: Type ITC
341
Intermediate metal conduit: IMC
342
Liquidtight flexible metal conduit: LFMC
350
Liquidtight flexible nonmetallic conduit: LFNC
356
Metal-clad cable: Type MC
330
Mineral-insulated, metal-sheathed cable: Type MI
332
Network-powered broadband communications cables
800 and 830
Nonmetallic-sheathed cable: Types NM, NMC, and NMS
334
Non-power-limited fire alarm cable
722 and 760
Optical fiber cables
722 and 770
Other factory-assembled, multiconductor control, signal, or power cables that are specifically approved for installation in cable trays
Power and control tray cable: Type TC
336
Power-limited fire alarm cable
722 and 760
Power-limited tray cable
725
Rigid metal conduit: RMC
344
Rigid polyvinyl chloride conduit: PVC
352
Reinforced thermosetting resin conduit: RTRC
355
Service-entrance cable: Types SE and USE
338
Underground feeder and branch-circuit cable: Type UF
340
[392.10(A)](https://2023.antflix.net#392.10(A)) | https://2023.antflix.net#392.10(A) |
Chapter 3 Wiring Methods and Materials | 392.10(B) | The wiring methods in Table 392.10(A) shall be permitted to be used in any industrial establishment under the conditions described in their respective articles. In industrial establishments only, where conditions of maintenance and supervision ensure that only qualified persons service the installed cable tray system, any of the cables in 392.10(B)(1) and (B)(2) shall be permitted to be installed in ladder, ventilated trough, solid bottom, or ventilated channel cable trays. [392.10(B)](https://2023.antflix.net#392.10(B)) | https://2023.antflix.net#392.10(B) |
Chapter 3 Wiring Methods and Materials | 392.10(B)(1) | Single-conductor cables and single insulated conductors shall be permitted to be installed in accordance with 392.10(B)(1)(a) through (B)(1)(c).Single-conductor cables and single insulated conductors shall be 1/0 AWG or larger and shall be of a type listed and marked on the surface for use in cable trays. Where 1/0 AWG through 4/0 AWG single-conductor cables and single insulated conductors are installed in ladder cable tray, the maximum allowable rung spacing for the ladder cable tray shall be 225 mm (9 in.).Welding cables shall comply with Article 630, Part IV.Single conductors used as equipment grounding conductors shall be insulated, covered, or bare, and they shall be 4 AWG or larger. [392.10(B)(1)](https://2023.antflix.net#392.10(B)(1)) | https://2023.antflix.net#392.10(B)(1) |
Chapter 3 Wiring Methods and Materials | 392.10(B)(2) | Single- and multiconductor medium voltage cables shall be Type MV cable. Single conductors shall be installed in accordance with 392.10(B)(1). [392.10(B)(2)](https://2023.antflix.net#392.10(B)(2)) | https://2023.antflix.net#392.10(B)(2) |
Chapter 3 Wiring Methods and Materials | 392.10(C) | Cable trays in hazardous (classified) locations shall contain only the cable types and raceways permitted by other articles in this Code. [392.10(C)](https://2023.antflix.net#392.10(C)) | https://2023.antflix.net#392.10(C) |
Chapter 3 Wiring Methods and Materials | 392.10(D) | In addition to the uses permitted elsewhere in 392.10, nonmetallic cable tray shall be permitted in corrosive areas and in areas requiring voltage isolation. [392.10(D)](https://2023.antflix.net#392.10(D)) | https://2023.antflix.net#392.10(D) |
Chapter 3 Wiring Methods and Materials | 392.10(E) | In airports where maintenance and supervision conditions ensure that only qualified persons can access, install, or service the cable, airfield lighting cable used in series circuits that are rated up to 5000 volts and are powered by constant current regulators shall be permitted to be installed in cable trays. Informational Note: Federal Aviation Administration (FAA) Advisory Circulars (ACs) provide additional practices and methods for airport lighting. [392.10(E)](https://2023.antflix.net#392.10(E)) | https://2023.antflix.net#392.10(E) |
Chapter 3 Wiring Methods and Materials | 392.12 | Cable tray systems shall not be used in hoistways or where subject to severe physical damage. [392.12](https://2023.antflix.net#392.12) | https://2023.antflix.net#392.12 |
Chapter 3 Wiring Methods and Materials | 392.18(A) | Cable trays shall be installed as a complete system. Field bends or modifications shall be so made that the electrical continuity of the cable tray system and support for the cables is maintained. Cable tray systems shall be permitted to have mechanically discontinuous segments between cable tray runs or between cable tray runs and equipment. [392.18(A)](https://2023.antflix.net#392.18(A)) | https://2023.antflix.net#392.18(A) |
Chapter 3 Wiring Methods and Materials | 392.18(B) | Each run of cable tray shall be completed before the installation of cables. [392.18(B)](https://2023.antflix.net#392.18(B)) | https://2023.antflix.net#392.18(B) |
Chapter 3 Wiring Methods and Materials | 392.18(C) | In portions of runs where additional protection is required, covers or enclosures providing the required protection shall be of a material that is compatible with the cable tray. [392.18(C)](https://2023.antflix.net#392.18(C)) | https://2023.antflix.net#392.18(C) |
Chapter 3 Wiring Methods and Materials | 392.18(D) | Cable trays shall be permitted to extend transversely through partitions and walls or vertically through platforms and floors in wet or dry locations where the installations, complete with installed cables, are made in accordance with 300.21. [392.18(D)](https://2023.antflix.net#392.18(D)) | https://2023.antflix.net#392.18(D) |
Chapter 3 Wiring Methods and Materials | 392.18(E) | Cable trays shall be exposed and accessible, except as permitted by 392.18(D). [392.18(E)](https://2023.antflix.net#392.18(E)) | https://2023.antflix.net#392.18(E) |
Chapter 3 Wiring Methods and Materials | 392.18(F) | Sufficient space shall be provided and maintained about cable trays to permit adequate access for installing and maintaining the cables. [392.18(F)](https://2023.antflix.net#392.18(F)) | https://2023.antflix.net#392.18(F) |
Chapter 3 Wiring Methods and Materials | 392.18(G) | In industrial facilities where conditions of maintenance and supervision ensure that only qualified persons service the installation and where the cable tray systems are designed and installed to support the load, such systems shall be permitted to support raceways and cables, and boxes and conduit bodies covered in 314.1. For raceways terminating at the tray, a listed cable tray clamp or adapter shall be used to securely fasten the raceway to the cable tray system. Additional supporting and securing of the raceway shall be in accordance with the appropriate raceway article. For raceways or cables running parallel to and attached to the bottom or side of a cable tray system, fastening and supporting shall be in accordance with the appropriate raceway or cable article. For boxes and conduit bodies attached to the bottom or side of a cable tray system, fastening and supporting shall be in accordance with 314.23. [392.18(G)](https://2023.antflix.net#392.18(G)) | https://2023.antflix.net#392.18(G) |
Chapter 3 Wiring Methods and Materials | 392.18(H) | Cable trays containing conductors operating over 600 volts shall have a permanent, legible warning notice carrying the wording "DANGER - HIGH VOLTAGE - KEEP AWAY" placed in a readily visible position on all cable trays, with the spacing of warning notices not to exceed 3 m (10 ft). The danger marking(s) or labels shall comply with 110.21 (B). Exception: Where not accessible (as applied to equipment), in industrial establishments where the conditions of maintenance and supervision ensure that only qualified persons service the installation, cable tray system warning notices shall be located where necessary for the installation to ensure safe maintenance and operation. [392.18(H)](https://2023.antflix.net#392.18(H)) | https://2023.antflix.net#392.18(H) |
Chapter 3 Wiring Methods and Materials | 392.20(A) | Multiconductor cables operating at 1000 volts or less shall be permitted to be installed in the same tray. [392.20(A)](https://2023.antflix.net#392.20(A)) | https://2023.antflix.net#392.20(A) |
Chapter 3 Wiring Methods and Materials | 392.20(B) | Cables operating at over 1000 volts and those operating at 1000 volts or less installed in the same cable tray shall comply with either of the following: The cables operating at over 1000 volts are Type MC.The cables operating at over 1000 volts are separated from the cables operating at 1000 volts or less by a solid fixed barrier of a material compatible with the cable tray. [392.20(B)](https://2023.antflix.net#392.20(B)) | https://2023.antflix.net#392.20(B) |
Chapter 3 Wiring Methods and Materials | 392.20(C) | Where single conductor cables comprising each phase, neutral, or grounded conductor of an alternating-current circuit are connected in parallel as permitted in 310.10(G), the conductors shall be installed in groups consisting of not more than one conductor per phase, neutral, or grounded conductor to prevent current imbalance in the paralleled conductors due to inductive reactance. Single conductors shall be securely bound in circuit groups to prevent excessive movement due to fault-current magnetic forces unless single conductors are cabled together, such as triplexed assemblies. [392.20(C)](https://2023.antflix.net#392.20(C)) | https://2023.antflix.net#392.20(C) |
Chapter 3 Wiring Methods and Materials | 392.20(D) | Where any of the single conductors installed in ladder or ventilated trough cable trays are 1/0 through 4/0 AWG, all single conductors shall be installed in a single layer. Conductors that are bound together to comprise each circuit group shall be permitted to be installed in other than a single layer. [392.20(D)](https://2023.antflix.net#392.20(D)) | https://2023.antflix.net#392.20(D) |
Chapter 3 Wiring Methods and Materials | 392.22(A) | The number of multiconductor cables, rated 2000 volts or less, permitted in a single cable tray shall not exceed the requirements of this section. The conductor sizes shall apply to both aluminum and copper conductors. Where dividers are used, fill calculations shall apply to each divided section of the cable tray. [392.22(A)](https://2023.antflix.net#392.22(A)) | https://2023.antflix.net#392.22(A) |
Chapter 3 Wiring Methods and Materials | 392.22(A)(1) | Where ladder or ventilated trough cable trays contain multiconductor power or lighting cables, or any mixture of multiconductor power, lighting, control, and signal cables, the maximum number of cables shall conform to 392.22(A)(1)(a) through (A)(1)(c).
Where all of the cables are 4/0 AWG or larger, the sum of the diameters of all cables shall not exceed the cable tray width, and the cables shall be installed in a single layer. Where the cable ampacity is determined according to 392.80(A)(1)(c), the cable tray width shall not be less than the sum of the diameters of the cables and the sum of the required spacing widths between the cables.
Where all of the cables are smaller than 4/0 AWG, the sum of the cross-sectional areas of all cables shall not exceed the maximum allowable cable fill area in Column 1 of Table 392.22(A)(1) for the appropriate cable tray width.
Where 4/0 AWG or larger cables are installed in the same cable tray with cables smaller than 4/0 AWG, the sum of the cross-sectional areas of all cables smaller than 4/0 AWG shall not exceed the maximum allowable fill area resulting from the calculation in Column 2 of Table 392.22(A)(1) for the appropriate cable tray width. The 4/0 AWG and larger cables shall be installed in a single layer, and no other cables shall be placed on them.
Table 392.22(A)(1) Allowable Cable Fill Area for Multiconductor Cables in Ladder, Ventilated Trough, or Solid Bottom Cable Trays for Cables Rated 2000 Volts or Less
Inside Width of Cable Tray
Maximum Allowable Fill Area for Multiconductor Cables
Ladder or Ventilated Trough or Wire Mesh Cable Trays, 392.22(A)(1)
Solid Bottom Cable Trays, 392.22(A)(3)
Column 1 Applicable for 392.22(A)(1)(b) Only
Column 2a Applicable for 392.22(A)(1)(c) Only
Column 3 Applicable for 392.22(A)(3)(b) Only
Column 4a Applicable for 392.22(A)(3)(c) Only
mm
in.
mm2
in.2
mm2
in.2
mm2
in.2
mm2
in.2
50
2.0
1,500
2.5
1,500—(30 Sd)b
2.5—(1.2 Sd)b
1,200
2.0
1,200—(25 Sd)b
2.0 — Sdb
100
4.0
3,000
4.5
3,000 — (30 Sd)b
4.5 — (1.2 Sd)
2,300
3.5
2,300 — (25 Sd)
3.5 — Sd
150
6.0
4,500
7.0
4,500 — (30 Sd)b
7 — (1.2 Sd)
3,500
5.5
3,500 — (25 Sd)b
5.5 — Sd
200
8.0
6,000
9.5
6,000 — (30 Sd)b
9.5 — (1.2 Sd)
4,500
7.0
4,500 — (25 Sd)
7.0 — Sd
225
9.0
6,800
10.5
6,800 — (30 Sd)
10.5 — (1.2 Sd)
5,100
8.0
5,100 — (25 Sd)
8.0 — Sd
300
12.0
9,000
14.0
9,000 — (30 Sd)
14 — (1.2 Sd)
7,100
11.0
7,100 — (25 Sd)
11.0 — Sd
400
16.0
12,000
18.5
12,000 — (30 Sd)
18.5 — (1.2 Sd)
9,400
14.5
9,400 — (25 Sd)
14.5 — Sd
450
18.0
13,500
21.0
13,500 — (30 Sd)
21 — (1.2 Sd)
10,600
16.5
10,600 — (25 Sd)
16.5 — Sd
500
20.0
15,000
23.5
15,000 — (30 Sd)
23.5 — (1.2 Sd)
11,800
18.5
11,800 — (25 Sd)
18.5 — Sd
600
24.0
18,000
28.0
18,000 — (30 Sd)
28 — (1.2 Sd)
14,200
22.0
14,200 — (25 Sd)
22.0 — Sd
750
30.0
22,500
35.0
22,500 — (30 Sd)
35 — (1.2 Sd)
17,700
27.5
17,700 — (25 Sd)
27.5 — Sd
900
36.0
27,000
42.0
27,000 — (30 Sd)
42 — (1.2 Sd)
21,300
33.0
21,300 — (25 Sd)
33.0 — Sd
aThe maximum allowable fill areas in Columns 2 and 4 shall be calculated. For example, the maximum allowable fill in mm2 for a 150-mm wide cable tray in Column 2 shall be 4500 minus (30 multiplied by Sd) [the maximum allowable fill, in square inches, for a 6-in. wide cable tray in Column 2 shall be 7 minus (1.2 multiplied by Sd)].
bThe term Sd in Columns 2 and 4 is equal to the sum of the diameters, in mm, of all cables 107.2 mm (in inches, of all 4/0 AWG) and larger multiconductor cables in the same cable tray with smaller cables. [392.22(A)(1)](https://2023.antflix.net#392.22(A)(1)) | https://2023.antflix.net#392.22(A)(1) |
Chapter 3 Wiring Methods and Materials | 392.22(A)(2) | Where a ladder or ventilated trough cable tray having a usable inside depth of 150 mm (6 in.) or less contains multiconductor control and/or signal cables only, the sum of the cross-sectional areas of all cables at any cross section shall not exceed 50 percent of the interior cross-sectional area of the cable tray. A depth of 150 mm (6 in.) shall be used to calculate the allowable interior cross-sectional area of any cable tray that has a usable inside depth of more than 150 mm (6 in.). [392.22(A)(2)](https://2023.antflix.net#392.22(A)(2)) | https://2023.antflix.net#392.22(A)(2) |
Chapter 3 Wiring Methods and Materials | 392.22(A)(3) | Where solid bottom cable trays contain multiconductor power or lighting cables, or any mixture of multiconductor power, lighting, control, and signal cables, the maximum number of cables shall conform to 392.22(A)(3)(a) through (A)(3)(c). Where all of the cables are 4/0 AWG or larger, the sum of the diameters of all cables shall not exceed 90 percent of the cable tray width, and the cables shall be installed in a single layer.Where all of the cables are smaller than 4/0 AWG, the sum of the cross-sectional areas of all cables shall not exceed the maximum allowable cable fill area in Column 3 of Table 392.22(A)(1) for the appropriate cable tray width.Where 4/0 AWG or larger cables are installed in the same cable tray with cables smaller than 4/0 AWG, the sum of the cross-sectional areas of all cables smaller than 4/0 AWG shall not exceed the maximum allowable fill area resulting from the computation in Column 4 of Table 392.22(A)(1) for the appropriate cable tray width. The 4/0 AWG and larger cables shall be installed in a single layer, and no other cables shall be placed on them. [392.22(A)(3)](https://2023.antflix.net#392.22(A)(3)) | https://2023.antflix.net#392.22(A)(3) |
Chapter 3 Wiring Methods and Materials | 392.22(A)(4) | Where a solid bottom cable tray having a usable inside depth of 150 mm (6 in.) or less contains multiconductor control and/or signal cables only, the sum of the cross sectional areas of all cables at any cross-section shall not exceed 40 percent of the interior cross-sectional area of the cable tray. A depth of 150 mm (6 in.) shall be used to calculate the allowable interior cross-sectional area of any cable tray that has a usable inside depth of more than 150 mm (6 in.). [392.22(A)(4)](https://2023.antflix.net#392.22(A)(4)) | https://2023.antflix.net#392.22(A)(4) |
Chapter 3 Wiring Methods and Materials | 392.22(A)(5) | Where ventilated channel cable trays contain multiconductor cables of any type, 392.22(A)(5)(a) and (A)(5)(b) shall apply. Where only one multiconductor cable is installed, the cross-sectional area shall not exceed the value specified in Column 1 of Table 392.22(A)(5).Where more than one multiconductor cable is installed, the sum of the cross-sectional area of all cables shall not exceed the value specified in Column 2 of Table 392.22(A)(5).Table 392.22(A)(5) Allowable Cable Fill Area for Multiconductor Cables in Ventilated Channel Cable Trays for Cables Rated 2000 Volts or Less
Inside Width of Cable Tray
Maximum Allowable Fill Area for Multiconductor Cables
Column 1 One Cable
Column 2 More Than One Cable
mm
in.
mm2
in.2
mm
in.
75
3
1500
2.3
850
1.3
100
4
2900
4.5
1600
2.5
150
6
4500
7.0
2450
3.8
[392.22(A)(5)](https://2023.antflix.net#392.22(A)(5)) | https://2023.antflix.net#392.22(A)(5) |
Chapter 3 Wiring Methods and Materials | 392.22(A)(6) | Where solid channel cable trays contain multiconductor cables of any type, 392.22(A)(6)(a) and (A)(6)(b) shall apply. Where only one multiconductor cable is installed, the cross-sectional area of the cable shall not exceed the value specified in Column 1 of Table 392.22(A)(6).Where more than one multiconductor cable is installed, the sum of the cross-sectional area of all cable shall not exceed the value specified in Column 2 of Table 392.22(A)(6).Table 392.22(A)(6) Allowable Cable Fill Area for Multiconductor Cables in Solid Channel Cable Trays for Cables Rated 2000 Volts or Less
Inside Width of Cable Tray
Column 1 One Cable
Column 2 More Than One Cable
mm
in.
mm2
in.2
mm2
in.2
50
2
850
1.3
500
0.8
75
3
1300
2.0
700
1.1
100
4
2400
3.7
1400
2.1
150
6
3600
5.5
2100
3.2
[392.22(A)(6)](https://2023.antflix.net#392.22(A)(6)) | https://2023.antflix.net#392.22(A)(6) |
Chapter 3 Wiring Methods and Materials | 392.22(B) | The number of single conductor cables, rated 2000 volts or less, permitted in a single cable tray section shall not exceed the requirements of this section. The single conductors, or conductor assemblies, shall be evenly distributed across the cable tray. The conductor sizes shall apply to both aluminum and copper conductors. [392.22(B)](https://2023.antflix.net#392.22(B)) | https://2023.antflix.net#392.22(B) |
Chapter 3 Wiring Methods and Materials | 392.22(B)(1) | Where ladder or ventilated trough cable trays contain single-conductor cables, the maximum number of single conductors shall conform to 392.22(B)(1)(a) through (B)(1)(d). Where all of the cables are 1000 kcmil or larger, the sum of the diameters of all single-conductor cables shall not exceed the cable tray width, and the cables shall be installed in a single layer. Conductors that are bound together to comprise each circuit group shall be permitted to be installed in other than a single layer.Where all of the cables are from 250 kcmil through 900 kcmil. the sum of the cross-sectional areas of all single-conductor cables shall not exceed the maximum allowable cable (ill area in Column 1 of Table 392.22(B)(1) for the appropriate cable tray width.Where 1000 kcmil or larger single-conductor cables are installed in the same cable tray with single-conductor cables smaller than 1000 kcmil, the sum of the cross sectional areas of all cables smaller than 1000 kcmil shall not exceed the maximum allowable fill area resulting from the computation in Column 2 of Table 392.22(B)(1) for the appropriate cable tray width.Where any of the single conductor cables are 1/0 through 4/0 AWG, the sum of the diameters of all single conductor cables shall not exceed the cable tray width.
Table 392.22(B)(1) Allowable Cable Fill Area for Single-Conductor Cables in Ladder, Ventilated Trough, or Wire Mesh Cable Trays for Cables Rated 2000 Volts or Less
Inside Width of Cable Tray
Maximum Allowable Fill Area for Single-Conductor Cables in Ladder, Ventilated Trough, or Wire Mesh Cable Trays
Column 1 Applicable for 392.22(B)(1)(b) Only
Column 2a Applicable for 392.22(B)(1)(c) Only
mm
in.
mm2
in.2
mm2
in.2
50
2
1,400
2.0
1.400 — (28 Sd)b
2.0 — (1.1 Sd)b
100
4
2,800
4.5
2,800 — (28 Sd)
4.5 — (1.1 Sd)
150
6
4,200
6.5
4,200 — (28 Sd)b
6.5 — (1.1 Sd)b
200
8
5,600
8.5
5,600 — (28 Sd)
8.5 — (1.1 Sd)
225
9
6,100
9.5
6,100 — (28 Sd)
9.5 — (1.1 Sd)
300
12
8,400
13.0
8,400 — (28 Sd)
13.0 — (1.1 Sd)
400
16
11,200
17.5
11,200 — (28 Sd)
17.5 — (1.1 Sd)
450
18
12,600
19.5
12,600 — (28 Sd)
19.5 — (1.1 Sd)
500
20
14,000
21.5
14,000 — (28 Sd)
21.5 — (1.1 Sd)
600
24
16,800
26.0
16,800 — (28 Sd)
26.0 — (1.1 Sd)
750
30
21,000
32.5
21,000 — (28 Sd)
32.5 — (1.1 Sd)
900
36
25,200
39.0
25,200 — (28 Sd)
39.0 — (1.1 Sd)
aThe maximum allowable fill areas in Column 2 shall be calculated. For example, the maximum allowable fill, in mm2, for a 150-mm wide cable tray in Column 2 shall be 4200 minus (28 multiplied by Sd) [the maximum allowable fill, in square inches, for a 6-in. wide cable tray in Column 2 shall be 6.5 minus (1.1 multiplied by Sd)].
bThe term Sd in Column 2 is equal to the sum of the diameters, in mm, of all cables 507 mm2 (in inches, of all 1000 kcmil) and larger single-conductor cables in the same cable tray with small cables. [392.22(B)(1)](https://2023.antflix.net#392.22(B)(1)) | https://2023.antflix.net#392.22(B)(1) |
Chapter 3 Wiring Methods and Materials | 392.22(B)(2) | Where 50 mm (2 in.), 75 mm (3 in.), 100 mm (4 in.), or 150 mm (6 in.) wide ventilated channel cable trays contain single-conductor cables, the sum of the diameters of all single conductors shall not exceed the inside width of the channel. [392.22(B)(2)](https://2023.antflix.net#392.22(B)(2)) | https://2023.antflix.net#392.22(B)(2) |
Chapter 3 Wiring Methods and Materials | 392.22(C) | The number of cables rated 2001 volts or over permitted in a single cable tray shall not exceed the requirements of this section.
The sum of the diameters of single-conductor and multiconductor cables shall not exceed the cable tray width, and the cables shall be installed in a single layer. Where single conductor cables are triplexed, quadruplexed, or bound together in circuit groups, the sum of the diameters of the single conductors shall not exceed the cable tray width, and these groups shall be installed in single layer arrangement. [392.22(C)](https://2023.antflix.net#392.22(C)) | https://2023.antflix.net#392.22(C) |
Chapter 3 Wiring Methods and Materials | 392.30(A) | Cable trays shall be supported at intervals in accordance with the installation instructions. [392.30(A)](https://2023.antflix.net#392.30(A)) | https://2023.antflix.net#392.30(A) |
Chapter 3 Wiring Methods and Materials | 392.30(B) | Cables and conductors shall be secured to and supported by the cable tray system in accordance with the following, as applicable: In other than horizontal runs, the cables shall be fastened securely to transverse members of the cable tray.Supports shall be provided to prevent stress on cables where they enter raceways from cable tray systems.The system shall provide for the support of cables and raceway wiring methods in accordance with their corresponding articles. Where cable trays support individual conductors or multiconductor cables and where the conductors or multiconductor cables pass from one cable tray to another, or from a cable tray to raceway(s) or from a cable tray to equipment where the conductors are terminated, the distance between the cable trays or between the cable tray and the raceway(s) or the equipment shall not exceed 1.8 m (6 ft). The conductors shall be secured to the cable tray(s) at the transition, and they shall be protected, by guarding or by location, from physical damage.Cable ties shall be listed and identified for the application and for securement and support. [392.30(B)](https://2023.antflix.net#392.30(B)) | https://2023.antflix.net#392.30(B) |
Chapter 3 Wiring Methods and Materials | 392.44 | Expansion splice plates for cable trays shall be provided where necessary to compensate for thermal expansion and contraction. [392.44](https://2023.antflix.net#392.44) | https://2023.antflix.net#392.44 |
Chapter 3 Wiring Methods and Materials | 392.46 | A box shall not be required where cables or conductors are installed in bushed conduit and tubing used for support or for protection against physical damage or where conductors or cables transition to a raceway wiring method from the cable tray. Conductors shall be permitted to enter equipment in accordance with 392.46(A) or (B). [392.46](https://2023.antflix.net#392.46) | https://2023.antflix.net#392.46 |
Chapter 3 Wiring Methods and Materials | 392.46(A) | Individual conductors or multiconductor cables with entirely nonmetallic sheaths shall be permitted to enter enclosures where they are terminated through nonflexible bushed conduit or tubing installed for their protection provided they are secured at the point of transition from the cable tray and the conduit or tubing is sealed at the outer end using an approved means so as to prevent debris from entering the equipment through the conduit or tubing. [392.46(A)](https://2023.antflix.net#392.46(A)) | https://2023.antflix.net#392.46(A) |
Chapter 3 Wiring Methods and Materials | 392.46(B) | Individual conductors or multiconductor cables with entirely nonmetallic sheaths shall be permitted to enter enclosures through openings associated with flanges from cable trays where the cable tray is attached to the flange and the flange is mounted directly to the equipment. The openings shall be made such that the conductors are protected from abrasion and the opening shall be sealed or covered to prevent debris from entering the enclosure through the opening. Informational Note: One method of preventing debris from entering the enclosure is to seal the outer end of the raceway or the opening with duct seal. [392.46(B)](https://2023.antflix.net#392.46(B)) | https://2023.antflix.net#392.46(B) |
Chapter 3 Wiring Methods and Materials | 392.56 | Cable splices and Type MV cable joints made and insulated by approved methods shall be permitted to be located within a cable tray, provided they are accessible. Splices and Type MV cable joints shall be permitted to project above the side rails where not subject to physical damage. [392.56](https://2023.antflix.net#392.56) | https://2023.antflix.net#392.56 |
Chapter 3 Wiring Methods and Materials | 392.60(A) | Metal cable trays shall be permitted to be used as equipment grounding conductors where continuous maintenance and supervision ensure that qualified persons service the installed cable tray system and the cable tray complies with this section. Metal cable trays that support electrical conductors shall be grounded as required for conductor enclosures in accordance with 250.96 and Part IV of Article 250. Metal cable trays containing only non-power conductors shall be electrically continuous through approved connections or the use of a bonding jumper. Informational Note: Examples of non-power conductors include nonconductive optical fiber cables and Class 2 and Class 3 remote-control, signaling, and power-limited circuits. [392.60(A)](https://2023.antflix.net#392.60(A)) | https://2023.antflix.net#392.60(A) |
Chapter 3 Wiring Methods and Materials | 392.60(B) | Steel or aluminum cable tray systems shall be permitted to be used as equipment grounding conductors, provided all the following requirements are met:
The cable tray sections and fittings are identified as an equipment grounding conductor.
The minimum cross-sectional area of cable trays conform to the requirements in Table 392.60(B).
All cable tray sections and fittings are legibly and durably marked to show the cross-sectional area of metal in channel cable trays, or cable trays of one-piece construction, and the total cross-sectional area of both side rails for ladder or trough cable trays.
Cable tray sections, fittings, and connected raceways are bonded in accordance with 250.96, using bolted mechanical connectors or bonding jumpers sized and installed in accordance with 250.102./li>
Table 392.60(B) Metal Area Requirements for Cable Trays Used as Equipment Grounding Conductor
Maximum Fuse Ampere Rating, Circuit Breaker Ampere Trip Setting, or Circuit Breaker Protective Relay Ampere Trip Setting for Ground-Fault Protection of Any Cable Circuit in the Cable Tray System
Minimum Cross-Sectional Area of Metal*
Steel Cable Trays
Aluminum Cable Trays
mm2
in.2
mm2
in.2
60
129
0.20
129
0.20
100
258
0.40
129
0.20
200
451.5
0.70
129
0.20
400
645
1.00
258
0.40
600
967.5
1.50†
258
0.40
1000
-
-
387
0.60
1200
-
-
645
1.00
1600
-
-
967.5
1.50
2000
-
-
1290
2.00†
*Total cross-sectional area of both side rails for ladder or trough cable trays; or the minimum cross-sectional area of metal in channel cable trays or cable trays of one-piece construction.
†Steel cable trays shall not be used as equipment grounding conductors for circuits with ground-fault protection above 600 amperes. Aluminum cable trays shall not be used as equipment grounding conductors for circuits with ground-fault protection above 2000 amperes. [392.60(B)](https://2023.antflix.net#392.60(B)) | https://2023.antflix.net#392.60(B) |
Chapter 3 Wiring Methods and Materials | 392.60(C) | Where metal cable tray systems are mechanically discontinuous, as permitted in 392.18(A), a bonding jumper sized in accordance with 250.102 shall connect the two sections of the cable tray, or the cable tray and the raceway or equipment. Bonding shall be in accordance with 250.96. [392.60(C)](https://2023.antflix.net#392.60(C)) | https://2023.antflix.net#392.60(C) |
Chapter 3 Wiring Methods and Materials | 392.80(A) | Informational Note: See 110.14(C) for conductor temperature limitations due to termination provisions. [392.80(A)](https://2023.antflix.net#392.80(A)) | https://2023.antflix.net#392.80(A) |
Chapter 3 Wiring Methods and Materials | 392.80(A)(1) | The ampacity of multiconductor cables, nominally rated 2000 volts or less, installed according to the requirements of 392.22(A) shall be as given in Table 310.16 and Table 310.18, subject to 392.80(A)(1)(a), (A)(1)(b), (A)(1)(c), and 310.14(A)(2). The adjustment factors of 310.15(C)(1) shall apply only to multiconductor cables with more than three current-carrying conductors. Adjustment factors shall be limited to the number of current-carrying conductors in the cable and not to the number of conductors in the cable tray.Where cable trays are continuously covered for more than 1.8 m (6 ft) with solid unventilated covers, not over 95 percent of the ampacities of Table 310.16 and Table 310.18 shall be permitted for multiconductor cables.Where multiconductor cables are installed in a single layer in uncovered trays, with a maintained spacing of not less than one cable diameter between cables, the ampacity shall not exceed the ambient temperature-corrected ampacities of multiconductor cables, with not more than three insulated conductors rated 0 through 2000 volts in free air, in accordance with 310.14(B).Informational Note: See Informative Annex B, Table B.2(3). [392.80(A)(1)](https://2023.antflix.net#392.80(A)(1)) | https://2023.antflix.net#392.80(A)(1) |
Chapter 3 Wiring Methods and Materials | 392.80(A)(2) | The ampacity of single-conductor cables shall be as permitted by 310.14(A)(2). The adjustment factors of 310.15(C)(1) shall not apply to the ampacity of cables in cable trays. The ampacity of single-conductor cables, or single conductors cabled together (triplexed, quadruplexed, and so forth), nominally rated 2000 volts or less, shall comply with 392.80(A)(2)(a) through (A)(2)(d). Where installed according to the requirements of 392.22(B), the ampacities for 600 kcmil and larger single-conductor cables in uncovered cable trays shall not exceed 75 percent of the ampacities in Table 310.17 and Table 310.19. Where cable trays are continuously covered for more than 1.8 m (6 ft) with solid unventilated covers, the ampacities for 600 kcmil and larger cables shall not exceed 70 percent of the ampacities in Table 310.17 and Table 310.19.Where installed according to the requirements of 392.22(B), the ampacities for 1/0 AWG through 500 kcmil single-conductor cables in uncovered cable trays shall not exceed 65 percent of the ampacities in Table 310.17 and Table 310.19. Where cable trays are continuously covered for more than 1.8 m (6 ft) with solid unventilated covers, the ampacities for 1/0 AWG through 500 kcmil cables shall not exceed 60 percent of the ampacities in Table 310.17 and Table 310.19.Where single conductors are installed in a single layer in uncovered cable trays, with a maintained space of not less than one cable diameter between individual conductors, the ampacity of 1/0 AWG and larger cables shall not exceed the ampacities in Table 310.17 and Table 310.19.Exception to (c): For solid bottom cable trays, the ampacity of single conductor cables shall be determined by 310.14(B).Where single conductors are installed in a triangular or square configuration in uncovered cable trays, with a maintained free airspace of not less than 2.15 times one conductor diameter (2.15 x O.D.) of the largest conductor contained within the configuration and adjacent conductor configurations or cables, the ampacity of 1/0 AWG and larger cables shall not exceed the ampacities of two or three single insulated conductors rated 0 through 2000 volts supported on a messenger in accordance with 310.15.Informational Note: See Table 310.20. [392.80(A)(2)](https://2023.antflix.net#392.80(A)(2)) | https://2023.antflix.net#392.80(A)(2) |
Chapter 3 Wiring Methods and Materials | 392.80(A)(3) | Where a cable tray contains a combination of multiconductor and single-conductor cables, the ampacities shall be as given in 392.80(A)(1) for multiconductor cables and 392.80(A)(2) for single-conductor cables, provided that the following conditions apply: The sum of the multiconductor cable fill area as a percentage of the allowable fill area for the tray calculated in accordance with 392.22(A), and the single-conductor cable fill area as a percentage of the allowable fill area for the tray calculated in accordance with 392.22(B), totals not more than 100 percent.Multiconductor cables are installed according to 392.22(A), and single-conductor cables are installed according to 392.22(B) and 392.22(C). [392.80(A)(3)](https://2023.antflix.net#392.80(A)(3)) | https://2023.antflix.net#392.80(A)(3) |
Chapter 3 Wiring Methods and Materials | 392.80(B) | The ampacity of cables, rated 2001 volts, nominal, or over, installed according to 392.22(C) shall not exceed the requirements of this section. Informational Note: See 110.40 for conductor temperature limitations due to termination provisions. [392.80(B)](https://2023.antflix.net#392.80(B)) | https://2023.antflix.net#392.80(B) |
Chapter 3 Wiring Methods and Materials | 392.80(B)(1) | The ampacity of multiconductor cables shall be as given in Table 315.60(C)(9) and Table 315.60(C)(10), subject to the following: Where cable trays are continuously covered for more than 1.8 m (6 ft) with solid unventilated covers, not more than 95 percent of the ampacities of Table 315.60(C)(9) and Table 315.60(C)(10) shall be permitted for multiconductor cables.Where multiconductor cables are installed in a single layer in uncovered cable trays, with maintained spacing of not less than one cable diameter between cables, the ampacity shall not exceed the allowable ampacities of Table 315.60(C)(5) and Table 315.60(C)(6). [392.80(B)(1)](https://2023.antflix.net#392.80(B)(1)) | https://2023.antflix.net#392.80(B)(1) |
Chapter 3 Wiring Methods and Materials | 392.80(B)(2) | The ampacity of single-conductor cables, or single conductors cabled together (triplexed, quadruplexed, and so forth), shall comply with the following: The ampacities for 1/0 AWG and larger single-conductor cables in uncovered cable trays shall not exceed 75 percent of the ampacities in Table 315.60(C)(3) and Table 315.60(C)(4). Where the cable trays are covered for more than 1.8 m (6 ft) with solid unventilated covers, the ampacities for 1/0 AWG and larger single-conductor cables shall not exceed 70 percent of the ampacities in Table 315.60(C)(3) and Table 315.60(C)(4).Where single-conductor cables are installed in a single layer in uncovered cable trays, with a maintained space of not less than one cable diameter between individual conductors, the ampacity of 1/0 AWG and larger cables shall not exceed the ampacities in Table 315.60(C)(3) and Table 315.60(C)(4).Where single conductors are installed in a triangular or square configuration in uncovered cable trays, with a maintained free air space of not less than 2.15 times the diameter (2.15 x O.D.) of the largest conductor contained within the configuration and adjacent conductor configurations or cables, the ampacity of 1/0 AWG and larger cables shall not exceed the ampacities in Table 315.60(C)(1) and Table 315.60(C)(2). [392.80(B)(2)](https://2023.antflix.net#392.80(B)(2)) | https://2023.antflix.net#392.80(B)(2) |
Chapter 3 Wiring Methods and Materials | 392.100(A) | Cable trays shall have suitable strength and rigidity to provide adequate support for all contained wiring. [392.100(A)](https://2023.antflix.net#392.100(A)) | https://2023.antflix.net#392.100(A) |
Chapter 3 Wiring Methods and Materials | 392.100(B) | Cable trays shall not have sharp edges, burrs, or projections that could damage the insulation or jackets of the wiring. [392.100(B)](https://2023.antflix.net#392.100(B)) | https://2023.antflix.net#392.100(B) |
Chapter 3 Wiring Methods and Materials | 392.100(C) | Cable tray systems shall be corrosion resistant. If made of ferrous material, the system shall be protected from corrosion as required by 300.6. [392.100(C)](https://2023.antflix.net#392.100(C)) | https://2023.antflix.net#392.100(C) |
Chapter 3 Wiring Methods and Materials | 392.100(D) | Cable trays shall have side rails or equivalent structural members. [392.100(D)](https://2023.antflix.net#392.100(D)) | https://2023.antflix.net#392.100(D) |
Chapter 3 Wiring Methods and Materials | 392.100(E) | Cable trays shall include fittings or other suitable means for changes in direction and elevation of runs. [392.100(E)](https://2023.antflix.net#392.100(E)) | https://2023.antflix.net#392.100(E) |
Chapter 3 Wiring Methods and Materials | 392.100(F) | Nonmetallic cable trays shall be made of flame-retardant material. [392.100(F)](https://2023.antflix.net#392.100(F)) | https://2023.antflix.net#392.100(F) |
Chapter 3 Wiring Methods and Materials | 393.1 | This article covers the installation of low-voltage suspended ceiling power distribution systems. [393.1](https://2023.antflix.net#393.1) | https://2023.antflix.net#393.1 |
Chapter 3 Wiring Methods and Materials | 393.6 | Suspended ceiling power distribution systems and associated fittings shall be listed as in 393.6(A) or (B). [393.6](https://2023.antflix.net#393.6) | https://2023.antflix.net#393.6 |
Chapter 3 Wiring Methods and Materials | 393.6(A) | Low-voltage suspended ceiling distribution systems operating at 30 volts ac or less or 60 volts dc or less shall be listed as a complete system, with the utilization equipment, power supply, and fittings as part of the same identified system. [393.6(A)](https://2023.antflix.net#393.6(A)) | https://2023.antflix.net#393.6(A) |
Chapter 3 Wiring Methods and Materials | 393.6(B) | A low-voltage suspended ceiling power distribution system assembled from the following parts, listed according to the appropriate function, shall be permitted: Listed low-voltage utilization equipmentListed Class 2 power supplyListed or identified fittings, including connectors and grid rails with bare conductorsListed low-voltage cables in accordance with 722.179, conductors in raceways, or other fixed wiring methods for the secondary circuit [393.6(B)](https://2023.antflix.net#393.6(B)) | https://2023.antflix.net#393.6(B) |
Chapter 3 Wiring Methods and Materials | 393.10 | Low-voltage suspended ceiling power distribution systems shall be permanently connected and shall be permitted as follows: For listed utilization equipment capable of operation at a maximum of 30 volts ac (42.4 volts peak) or 60 volts dc (24.8 volts peak for dc interrupted at a rate of 10 Hz to 200 Hz) and limited to Class 2 power levels in Chapter 9, Table 11(A) and Table 11(B) for lighting, control, and signaling circuits.In indoor dry locations.For residential, commercial, and industrial installations.In other spaces used for environmental air in accordance with 300.22(C), electrical equipment having a metal enclosure, or with a nonmetallic enclosure and fittings, shall be listed for use within an air-handling space and shall have adequate fire-resistant and low-smoke-producing characteristics and associated wiring material suitable for the ambient temperature.Informational Note: See ANSI/UL 2043-2018, Fire Test for Heat and Visible Smoke Release for Discrete Products and Their Accessories Installed in Air-Handling Spaces, for one method of defining adequate fire-resistant and low-smoke-producing characteristics for electrical equipment with a nonmetallic enclosure. [393.10](https://2023.antflix.net#393.10) | https://2023.antflix.net#393.10 |
Chapter 3 Wiring Methods and Materials | 393.12 | Suspended ceiling power distribution systems shall not be installed in the following: In damp or wet locationsWhere subject to corrosive fumes or vapors, such as storage battery roomsWhere subject to physical damageIn concealed locationsIn hazardous (classified) locationsAs part of a fire-rated floor-ceiling or roof-ceiling assembly, unless specifically listed as part of the assemblyFor lighting in general or critical patient care areas [393.12](https://2023.antflix.net#393.12) | https://2023.antflix.net#393.12 |
Chapter 3 Wiring Methods and Materials | 393.14(A) | Support wiring shall be installed in a neat and workmanlike manner. Cables and conductors installed exposed on the surface of ceilings and sidewalls shall be supported by the building structure in such a manner that the cable is not damaged by normal building use. Such cables shall be supported by straps, staples, hangers, cable ties listed and identified for securement and support, or similar fittings designed and installed so as not to damage the cable. Informational Note: Suspended ceiling low-voltage power grid distribution systems should be installed by qualified persons in accordance with the manufacturer's installation instructions. [393.14(A)](https://2023.antflix.net#393.14(A)) | https://2023.antflix.net#393.14(A) |
Chapter 3 Wiring Methods and Materials | 393.14(B) | Exposed insulated secondary circuit conductors shall be listed, of the type, and installed as described as follows: Class 2 cable supplied by a listed Class 2 power source and installed in accordance with Part I of Article 722 and Parts I and II of Article 725Wiring methods described in Chapter 3 [393.14(B)](https://2023.antflix.net#393.14(B)) | https://2023.antflix.net#393.14(B) |
Chapter 3 Wiring Methods and Materials | 393.21(A) | A disconnecting means for the Class 2 supply to the power grid system shall be located so as to be accessible and within sight of the Class 2 power source for servicing or maintenance of the grid system. [393.21(A)](https://2023.antflix.net#393.21(A)) | https://2023.antflix.net#393.21(A) |
Chapter 3 Wiring Methods and Materials | 393.21(B) | Where connected to a multiwire branch circuit, the disconnecting means shall simultaneously disconnect all the supply conductors, including the grounded conductors. [393.21(B)](https://2023.antflix.net#393.21(B)) | https://2023.antflix.net#393.21(B) |
Chapter 3 Wiring Methods and Materials | 393.30(A) | A suspended ceiling low-voltage power distribution system shall be secured to the mounting surface of the building structure by hanging wires, screws, or bolts in accordance with the installation and operation instructions. Mounting hardware, such as screws or bolts, shall be either packaged with the suspended ceiling low-voltage lighting power distribution system, or the installation instructions shall specify the types of mounting fasteners to be used. [393.30(A)](https://2023.antflix.net#393.30(A)) | https://2023.antflix.net#393.30(A) |
Chapter 3 Wiring Methods and Materials | 393.30(B) | The individual power grid rails shall be mechanically secured to the overall ceiling grid assembly. [393.30(B)](https://2023.antflix.net#393.30(B)) | https://2023.antflix.net#393.30(B) |
Chapter 3 Wiring Methods and Materials | 393.40(A) | Connections to busbar grid rails, cables, and conductors shall be made with listed insulating devices, and these connections shall be accessible after installation. A soldered connection shall be made mechanically secure before being soldered. Other means of securing leads, such as push-on terminals and spade-type connectors, shall provide a secure mechanical connection. The following connectors shall be permitted to be used as connection or interconnection devices: Load connectors shall be used for power from the busbar to listed utilization equipment.A pendant connector shall be permitted to suspend low-voltage luminaires or utilization equipment below the grid rail and to supply power from the busbar to the utilization equipment.A power feed connector shall be permitted to connect the power supply directly to a power distribution cable and to the busbar.Rail-to-rail connectors shall be permitted to interconnect busbars from one ceiling grid rail to another grid rail.Informational Note: See UL 310, Standard for Electrical Quick-Connect Terminals, for quick-connect terminals. See UL 486A-486B, Standard for Wire Connectors, for mechanical splicing devices. [393.40(A)](https://2023.antflix.net#393.40(A)) | https://2023.antflix.net#393.40(A) |
Chapter 3 Wiring Methods and Materials | 393.40(B) | Where made in a wall, connections shall be installed in an enclosure in accordance with Parts I, II, and III of Article 314. [393.40(B)](https://2023.antflix.net#393.40(B)) | https://2023.antflix.net#393.40(B) |
Chapter 3 Wiring Methods and Materials | 393.45(A) | The listed Class 2 power supply or transformer primary shall be protected at not greater than 20 amperes. [393.45(A)](https://2023.antflix.net#393.45(A)) | https://2023.antflix.net#393.45(A) |
Chapter 3 Wiring Methods and Materials | 393.45(B) | Listed Class 2 sources shall not have the output connections paralleled or otherwise interconnected unless listed for such interconnection. [393.45(B)](https://2023.antflix.net#393.45(B)) | https://2023.antflix.net#393.45(B) |
Chapter 3 Wiring Methods and Materials | 393.45(C) | A suspended ceiling low-voltage power distribution system shall be permitted to have reverse polarity (backfeed) protection of dc circuits by one of the following means: If the power supply is provided as part of the system, the power supply is provided with reverse polarity (backfeed) protection; orIf the power supply is not provided as part of the system, reverse polarity or backfeed protection can be provided as part of the grid rail busbar or as a part of the power feed connector. [393.45(C)](https://2023.antflix.net#393.45(C)) | https://2023.antflix.net#393.45(C) |
Chapter 3 Wiring Methods and Materials | 393.56 | A busbar splice shall be provided with insulation and mechanical protection equivalent to that of the grid rail busbars involved. [393.56](https://2023.antflix.net#393.56) | https://2023.antflix.net#393.56 |
Chapter 3 Wiring Methods and Materials | 393.57 | Connections in busbar grid rails, cables, and conductors shall be made with listed insulating devices and be accessible after installation. Where made in a wall, connections shall be installed in an enclosure in accordance with Parts I, II, and III of Article 314, as applicable. [393.57](https://2023.antflix.net#393.57) | https://2023.antflix.net#393.57 |
Chapter 3 Wiring Methods and Materials | 393.60 | The supply side of the Class 2 power source shall be connected to an equipment grounding conductor in accordance with the applicable requirements in Part IV of Article 250. [393.60](https://2023.antflix.net#393.60) | https://2023.antflix.net#393.60 |
Chapter 3 Wiring Methods and Materials | 393.61 | Class 2 load side circuits for suspended ceiling low-voltage power grid distribution systems shall be permitted to be grounded. [393.61](https://2023.antflix.net#393.61) | https://2023.antflix.net#393.61 |
Chapter 3 Wiring Methods and Materials | 393.100(A) | Current-carrying conductors for load side utilization equipment shall be copper and shall be 18 AWG minimum. Exception: Conductors of a size smaller than 18 AWG, but not smaller than 24 AWG, shall be permitted to be used for Class 2 circuits. Where used, these conductors shall be installed using a Chapter 3 wiring method, shall be totally enclosed, shall not be subject to movement or strain, and shall comply with the ampacity requirements in Table 522.22. [393.100(A)](https://2023.antflix.net#393.100(A)) | https://2023.antflix.net#393.100(A) |
Chapter 3 Wiring Methods and Materials | 393.100(B) | The power feed bus rail shall be 16 AWG minimum or equivalent. For a busbar with a circular cross section, the diameter shall be 1.29 mm (0.051 in.) minimum, and, for other than circular busbars, the area shall be 1.32 mm2 (0.002 in.2) minimum. [393.100(B)](https://2023.antflix.net#393.100(B)) | https://2023.antflix.net#393.100(B) |
Chapter 3 Wiring Methods and Materials | 394.1 | This article covers the use, installation, and construction specifications of concealed knob-and-tube wiring. [394.1](https://2023.antflix.net#394.1) | https://2023.antflix.net#394.1 |
Chapter 3 Wiring Methods and Materials | 394.10 | Concealed knob-and-tube wiring shall be permitted to be installed in the hollow spaces of walls and ceilings, or in unfinished attics and roof spaces as provided by 394.23, only as follows: For extensions of existing installationsElsewhere by special permission [394.10](https://2023.antflix.net#394.10) | https://2023.antflix.net#394.10 |
Chapter 3 Wiring Methods and Materials | 394.12 | Concealed knob-and-tube wiring shall not be used in the following: Commercial garagesTheaters and similar locationsMotion picture studiosHazardous (classified) locationsHollow spaces of walls, ceilings, and attics where such spaces are insulated by loose, rolled, or foamed-in-place insulating material that envelops the conductors [394.12](https://2023.antflix.net#394.12) | https://2023.antflix.net#394.12 |
Chapter 3 Wiring Methods and Materials | 394.17 | Conductors shall comply with 398.17 where passing through holes in structural members. Where passing through wood cross members in plastered partitions, conductors shall be protected by noncombustible, nonabsorbent, insulating tubes extending not less than 75 mm (3 in.) beyond the wood member. [394.17](https://2023.antflix.net#394.17) | https://2023.antflix.net#394.17 |
Chapter 3 Wiring Methods and Materials | 394.19(A) | A clearance of not less than 75 mm (3 in.) shall be maintained between conductors and a clearance of not less than 25 mm (1 in.) between the conductor and the surface over which it passes. [394.19(A)](https://2023.antflix.net#394.19(A)) | https://2023.antflix.net#394.19(A) |
Chapter 3 Wiring Methods and Materials | 394.19(B) | Where space is too limited to provide these minimum clearances, such as at meters, panelboards, outlets, and switch points, the individual conductors shall be enclosed in flexible nonmetallic tubing, which shall be continuous in length between the last support and the enclosure or terminal point. [394.19(B)](https://2023.antflix.net#394.19(B)) | https://2023.antflix.net#394.19(B) |
Chapter 3 Wiring Methods and Materials | 394.19(C) | Conductors shall comply with 398.19 for clearances from other exposed conductors, piping, and so forth. [394.19(C)](https://2023.antflix.net#394.19(C)) | https://2023.antflix.net#394.19(C) |
Chapter 3 Wiring Methods and Materials | 394.23 | Conductors in unfinished attics and roof spaces shall comply with 394.23(A) or (B). Informational Note: See 310.14(A)(3) for temperature limitation of conductors. [394.23](https://2023.antflix.net#394.23) | https://2023.antflix.net#394.23 |
Chapter 3 Wiring Methods and Materials | 394.23(A) | Conductors shall be installed along the side of or through bored holes in floor joists, studs, or rafters. Where run through bored holes, conductors in the joists and in studs or rafters to a height of not less than 2.1 m (7 ft) above the floor or floor joists shall be protected by substantial running boards extending not less than 25 mm (1 in.) on each side of the conductors. Running boards shall be securely fastened in place. Running boards and guard strips shall not be required where conductors are installed along the sides of joists, studs, or rafters. [394.23(A)](https://2023.antflix.net#394.23(A)) | https://2023.antflix.net#394.23(A) |
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