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Section E3907 Cabinets and Panelboards
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Where the wiring space of enclosures for switches or overcurrent devices contains conductors that are feeding through, spliced, or tapping off to other enclosures, switches, or overcurrent devices, all of the following conditions shall apply:
- The total area of all conductors installed at any cross section of the wiring space shall not exceed 40 percent of the cross-sectional area of that space.
- The total area of all conductors, splices, and taps installed at any cross section of the wiring space shall not exceed 75 percent of the cross-sectional area of that space.
- A warning label shall be applied to the enclosure that identifies the closest disconnecting means for any feed-through conductors. (312.8)
Where the wiring space of enclosures for switches or overcurrent devices contains power monitoring equipment, all of the following conditions shall be met:
- The power monitoring equipment shall be identified as a field installable accessory as part of the listed equipment, or shall be a listed kit evaluated for field installation in switch or overcurrent device enclosures.
- The total area of all conductors, splices, taps and equipment at any cross section of the wiring space shall not exceed 75 percent of the cross-sectional area of that space.
In damp or wet locations, cabinets and panelboards of the surface type shall be placed or equipped so as to prevent moisture or water from entering and accumulating within the cabinet, and shall be mounted to provide an air-space not less than 1/4 inch (6.4 mm) between the enclosure and the wall or other supporting surface. Cabinets installed in wet locations shall be weatherproof. For enclosures in wet locations, raceways and cables entering above the level of uninsulated live parts shall be installed with fittings listed for wet locations. (312.2)
Exception: Nonmetallic enclosures installed on concrete, masonry, tile, or similar surfaces shall not be required to be installed with an air space between the enclosure and the wall or supporting surface. (312.2 Exception)
In walls of concrete, tile or other noncombustible material, cabinets and panelboards shall be installed so that the front edge of the cabinet will not set back of the finished surface more than 1/4 inch (6.4 mm). In walls constructed of wood or other combustible material, cabinets shall be flush with the finished surface or shall project therefrom. (312.3)
Noncombustible surfaces that are broken or incomplete shall be repaired so that there will not be gaps or open spaces greater than 1/8 inch (3.2 mm) at the edge of the cabinet or cutout box employing a flush-type cover. (312.4)
Unused openings, other than those intended for the operation of equipment, those intended for mounting purposes, and those permitted as part of the design for listed equipment, shall be closed to afford protection substantially equivalent to that of the wall of the equipment. Metal plugs and plates used with nonmetallic cabinets shall be recessed at least 1/4 inch (6.4 mm) from the outer surface. Unused openings for circuit breakers and switches shall be closed using identified closures, or other approved means that provide protection substantially equivalent to the wall of the enclosure. (110.12(A)]
Conductors entering cabinets and panelboards shall be protected from abrasion and shall comply with Section E3906.1.1. (312.5)
Openings through which conductors enter cabinets, panelboards and meter sockets shall be closed in an approved manner. [312.5(A)]
Where cables are used, each cable shall be secured to the cabinet, panelboard, cutout box, or meter socket enclosure. [312.5(C)]
Exception: Cables with entirely nonmetallic sheaths shall be permitted to enter the top of a surface-mounted enclosure through one or more sections of rigid raceway not less than 18 inches (457 mm) nor more than 10 feet (3048 mm) in length, provided all the following conditions are met:
- Each cable is fastened within 12 inches (305 mm), measured along the sheath, of the outer end of the raceway.
- The raceway extends directly above the enclosure and does not penetrate a structural ceiling.
- A fitting is provided on each end of the raceway to protect the cable(s) from abrasion and the fittings remain accessible after installation.
- The raceway is sealed or plugged at the outer end using approved means so as to prevent access to the enclosure through the raceway.
- The cable sheath is continuous through the raceway and extends into the enclosure beyond the fitting not less than 1/4 inch (6.4 mm).
- The raceway is fastened at its outer end and at other points in accordance with Section E3802.1.
- The allowable cable fill for conduit or tubing shall not exceed that permitted by Table E3907.8 and shall be considered as a complete conduit or tubing system. A multiconductor cable having two or more conductors shall be treated as a single conductor for calculating the percentage of conduit fill area. For cables that have elliptical cross sections, the cross-sectional area calculation shall be based on the major diameter of the ellipse as a circle diameter. [312.5(C) Exception]
TABLE E3907.8 (Chapter 9, Table 1)
PERCENT OF CROSS SECTION OF CONDUIT AND TUBING FOR CONDUCTORS
| NUMBER OF CONDUCTORS | MAXIMUM PERCENT OF CONDUIT AND TUBING AREA FILLED BY CONDUCTORS |
| 1 | 53 |
| 2 | 31 |
| Over 2 | 40 |
The top and bottom wire-bending space for a panelboard enclosure shall be sized in accordance with Table E3907.9.1(1) based on the largest conductor entering or leaving the enclosure. [408.55 (A)]
Exceptions:
- For a panelboard rated at 225 amperes or less and designed to contain not more than 42 overcurrent devices, either the top or bottom wire-bending space shall be permitted to be sized in accordance with Table E3907.9.1(2). For the purposes of this exception, a 2-pole or a 3-pole circuit breaker shall be considered as two or three overcurrent devices, respectively. [408.55(A) Exception No. 1]
- For any panelboard, either the top or bottom wire-bending space shall be permitted to be sized in accordance with Table E3907.9.1(2) where the wire-bending space on at least one side is sized in accordance with Table E3907.9.1(1) based on the largest conductor to be terminated in any side wire-bending space. [408.55(A) Exception No. 2]
- Where the panelboard is designed and constructed for wiring using only a single 90-degree bend for each conductor, including the grounded circuit conductor, and the wiring diagram indicates and specifies the method of wiring that must be used, the top and bottom wire-bending space shall be permitted to be sized in accordance with Table E3907.9.1(2). [408.55(A) Exception No. 3]
- Where there are no conductors terminated in that space, either the top or the bottom wire-bending space, shall be permitted to be sized in accordance with Table E3907.9.1(2). [408.55(A) Exception No. 4]
TABLE E3907.9.1(1) [Table 312.6(B)]
MINIMUM WIRE-BENDING SPACE AT TERMINALS (see Note 1)
| WIRE SIZE (AWG or kcmil) | WIRES PER TERMINAL | ||||
| All other conductors | Compact stranded AA-8000 aluminum alloy conductors (see Note 3) | One (see Note 2) | Two | ||
| inches | mm | inches | mm | ||
| 14-10 | 12-8 | Not specified | Not specified | — | — |
| 8 | 6 | 11/2 | 38.1 | — | — |
| 6 | 4 | 2 | 50.8 | — | — |
| 4 | 2 | 3 | 76.2 | — | — |
| 3 | 1 | 3 | 76.2 | — | — |
| 2 | 1/0 | 31/2 | 88.9 | — | — |
| 1 | 2/0 | 41/2 | 114 | — | — |
| 1/0 | 3/0 | 51/2 | 140 | 51/2 | 140 |
| 2/0 | 4/0 | 6 | 152 | 6 | 152 |
| 3/0 | 250 | 61/2a | 165a | 61/2a | 165a |
| 4/0 | 300 | 7b | 178b | 71/2c | 190c |
| 250 | 350 | 81/2d | 216d | 81/2d | 229d |
| 300 | 400 | 10c | 254c | 10d | 254d |
| 350 | 500 | 12c | 305c | 12c | 305c |
| 400 | 600 | 13c | 330c | 13c | 330c |
| 500 | 700-750 | 14c | 356c | 14c | 356c |
| 600 | 800-900 | 15c | 381c | 16c | 406c |
| 700 | 1000 | 16c | 406c | 18c | 457c |
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
- Bending space at terminals shall be measured in a straight line from the end of the lug or wire connector in a direction perpendicular to the enclosure wall.
- For removable and lay-in wire terminals intended for only one wire, bending space shall be permitted to be reduced by the following number of millimeters (inches):
- 1/2 inches (12.7 mm)
- 1 inches (25.4 mm)
- 11/2 inches (38.1 mm)
- 2 inches (50.8 mm)
- This column shall be permitted to determine the required wire-bending space for compact stranded aluminum conductors in sizes up to 1000 kcmil and manufactured using AA-8000 series electrical grade aluminum alloy conductor material.
TABLE E3907.9.1(2) [Table 312.6(A)]
MINIMUM WIRE-BENDING SPACE AT TERMINALS AND MINIMUM WIDTH OF WIRING GUTTERS (see Note 1)
| ALL OTHER CONDUCTORS | COMPACT STRANDED AA-8000 ALUMINUM ALLOY CONDUCTORS (see Note 2) | WIRES PER TERMINAL | |||
| One | Two | ||||
| inches | mm | inches | mm | ||
| 14-10 | 12-8 | Not specified | Not specified | — | — |
| 8-6 | 6-4 | 11/2 | 38.1 | — | — |
| 4-3 | 2-1 | 2 | 50.8 | — | — |
| 2 | 1/0 | 21/2 | 63.5 | — | — |
| 1 | 2/0 | 3 | 76.2 | — | — |
| 1/0-2/0 | 3/0-4/0 | 31/2 | 88.9 | 5 | 127 |
| 3/0-4/0 | 250-300 | 4 | 102 | 6 | 152 |
| 250 | 350 | 41/2 | 114 | 6 | 152 |
| 300-350 | 400-500 | 5 | 127 | 8 | 203 |
| 400-500 | 600-750 | 6 | 152 | 8 | 203 |
| 600-700 | 800-1000 | 8 | 203 | 10 | 254 |
| 750-900 | — | 8 | 203 | 12 | 305 |
| 1000-1250 | — | 10 | 254 | — | — |
| 1500-2000 | — | 12 | 305 | — | — |
Notes:
- Bending space at terminals shall be measured in a straight line from the end of the lug or wire connector (in the direction that the wire leaves the terminal) to the wall, barrier, or obstruction.
- This column shall be permitted to be used to determine the minimum wirebending space for compact stranded aluminum conductors in sizes up to 1000 kcmil and manufactured using AA-8000 series electrical grade aluminum alloy conductor material in accordance with 310.106(B). The minimum width of the wire gutter space shall be determined using the all other conductors value in this table.
Side wire-bending space shall be in accordance with Table E3907.9.1(2) based on the largest conductor to be terminated in that space. [408.55(B)]
The distance between the center of the rear entry and the nearest termination for the entering conductors shall be not less than the distance given in Table E3907.9.1(1). Where a raceway or cable entry is in the wall of the enclosure, opposite a removable cover, the distance from that wall to the cover shall be permitted to comply with the distance required in Table E3907.9.1(2). [408.55 (C)]
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