Article 366

Auxiliary Gutters

Part I. General

1. Scope. This article covers the use, installation, and construction requirements of metal auxiliary gutters and nonmetallic auxiliary gutters and associated fittings.
2. Definitions.

Metal Auxiliary Gutter. A sheet metal enclosure used to supplement wiring spaces at meter centers, distribution centers, switchgear, switchboards, and similar points of wiring systems. The enclosure has hinged or removable covers for housing and protecting electrical wires, cable, and busbars. The enclosure is designed for conductors to be laid or set in place after the enclosures have been installed as a complete system.

366.6 ARTICLE 366 — AUXILIARY GUTTERS

Nonmetallic Auxiliary Gutter. A flame-retardant, nonmetallic enclosure used to supplement wiring spaces at meter centers, distribution centers, switchgear, switchboards, and similar points of wiring systems. The enclosure has hinged or remova‐ ble covers for housing and protecting electrical wires, cable, and busbars. The enclosure is designed for conductors to be laid or set in place after the enclosures have been installed as a complete system.

366.6 Listing Requirements.

1. Outdoors. Nonmetallic auxiliary gutters installed outdoors shall be listed for all of the following conditions:
   1. Exposure to sunlight
   2. Use in wet locations
   3. Maximum ambient temperature of the installation
2. Indoors. Nonmetallic auxiliary gutters installed indoors shall be listed for the maximum ambient temperature of the installation.

Part II. Installation

366.10 Uses Permitted.

1. Sheet Metal Auxiliary Gutters.
   1. Indoor and Outdoor Use. Sheet metal auxiliary gutters shall be permitted for indoor and outdoor use.
   2. Wet Locations. Sheet metal auxiliary gutters installed in wet locations shall be suitable for such locations.
2. Nonmetallic Auxiliary Gutters. Nonmetallic auxiliary gutters shall be listed for the maximum ambient temperature of the installation and marked for the installed conductor insu‐ lation temperature rating.Informational Note: Extreme cold may cause nonmetallic auxili‐ ary gutters to become brittle and therefore more susceptible to damage from physical contact.
   1. Outdoors. Nonmetallic auxiliary gutters shall be permit‐ ted to be installed outdoors where listed and marked as suita‐ ble for the purpose.
   2. Indoors. Nonmetallic auxiliary gutters shall be permitted to be installed indoors.

366.12 Uses Not Permitted. Auxiliary gutters shall not be used:

1. To enclose switches, overcurrent devices, appliances, or other similar equipment
2. To extend a greater distance than 9 m (30 ft) beyond the equipment that it supplements

Exception: As permitted in 620.35 for elevators, an auxiliary gutter shall be permitted to extend a distance greater than 9 m (30 ft) beyond the equipment it supplements.

Informational Note: For wireways, see Articles 376 and 378. For busways, see Article 368.

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366.20 Conductors Connected in Parallel. 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(H), 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 reac‐ tance.

1. Number of Conductors.
   1. Sheet Metal Auxiliary Gutters. The sum of the cross- sectional areas of all contained conductors and cables at any cross section of a sheet metal auxiliary gutter shall not exceed20 percent of the interior cross-sectional area of the sheet metal auxiliary gutter. The adjustment factors in 310.15(B)(3)(a) shall be applied only where the number of current-carrying conductors, including neutral conductors clas‐ sified as current-carrying under the provisions of 310.15(B)(5), exceeds 30. Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as current-carrying conductors.
   2. Nonmetallic Auxiliary Gutters. The sum of cross-sectional areas of all contained conductors and cables at any cross section of the nonmetallic auxiliary gutter shall not exceed 20 percent of the interior cross-sectional area of the nonmetal‐ lic auxiliary gutter.
2. Ampacity of Conductors.

1. Sheet Metal Auxiliary Gutters. Where the number of current-carrying conductors contained in the sheet metal auxil‐ iary gutter is 30 or less, the adjustment factors specified in 310.15(B)(3)(a) shall not apply. The current carried continu‐ ously in bare copper bars in sheet metal auxiliary gutters shall not exceed 1.55 amperes/mm2 (1000 amperes/in.2) of cross section of the conductor. For aluminum bars, the current carried continuously shall not exceed 1.09 amperes/mm2 (700 amperes/in.2) of cross section of the conductor.
2. Nonmetallic Auxiliary Gutters. The adjustment factors specified in 310.15(B)(3)(a) shall be applicable to the current- carrying conductors in the nonmetallic auxiliary gutter.

366.30 Securing and Supporting.

1. Sheet Metal Auxiliary Gutters. Sheet metal auxiliary gutters shall be supported and secured throughout their entire length at intervals not exceeding 1.5 m (5 ft).
2. Nonmetallic Auxiliary Gutters. Nonmetallic auxiliary gutters shall be supported and secured at intervals not to exceed 900 mm (3 ft) and at each end or joint, unless listed for other support intervals. In no case shall the distance between supports exceed 3 m (10 ft).

366.44 Expansion Fittings. Expansion fittings shall be instal‐ led where expected length change, due to expansion and contraction due to temperature change, is more than 6 mm (0.25 in.).

366.56 Splices and Taps. Splices and taps shall comply with 366.56(A) through (D).

1. Within Gutters. Splices or taps shall be permitted within gutters where they are accessible by means of removable covers or doors. The conductors, including splices and taps, shall not fill the gutter to more than 75 percent of its area.
2. Bare Conductors. Taps from bare conductors shall leave the gutter opposite their terminal connections, and conductors shall not be brought in contact with uninsulated current- carrying parts of different voltages.ARTICLE 368 — BUSWAYS 368.10
3. Suitably Identified. All taps shall be suitably identified at the gutter as to the circuit or equipment that they supply.
4. Overcurrent Protection. Tap connections from conduc‐ tors in auxiliary gutters shall be provided with overcurrent protection as required in 240.21.

366.58 Insulated Conductors.

1. Deflected Insulated Conductors. Where insulated conductors are deflected within an auxiliary gutter, either at the ends or where conduits, fittings, or other raceways or cables enter or leave the gutter, or where the direction of the gutter is deflected greater than 30 degrees, dimensions corresponding to one wire per terminal in Table 312.6(A) shall apply.
2. Auxiliary Gutters Used as Pull Boxes. Where insulated conductors 4 AWG or larger are pulled through an auxiliary gutter, the distance between raceway and cable entries enclos‐ ing the same conductor shall not be less than that required in 314.28(A)(1) for straight pulls and 314.28(A)(2) for angle pulls.

366.60 Grounding. Metal auxiliary gutters shall be connected to an equipment grounding conductor(s), to an equipment bonding jumper, or to the grounded conductor where permit‐ ted or required by 250.92(B)(1) or 250.142.

Part III. Construction Specifications

366.100 Construction.

1. Electrical and Mechanical Continuity. Gutters shall be constructed and installed so that adequate electrical and mechanical continuity of the complete system is secured.
2. Substantial Construction. Gutters shall be of substantial construction and shall provide a complete enclosure for the contained conductors. All surfaces, both interior and exterior, shall be suitably protected from corrosion. Corner joints shall be made tight, and where the assembly is held together by rivets, bolts, or screws, such fasteners shall be spaced not more than 300 mm (12 in.) apart.
3. Smooth Rounded Edges. Suitable bushings, shields, or fittings having smooth, rounded edges shall be provided where conductors pass between gutters, through partitions, around bends, between gutters and cabinets or junction boxes, and at other locations where necessary to prevent abrasion of the insu‐ lation of the conductors.
4. Covers. Covers shall be securely fastened to the gutter.
5. Clearance of Bare Live Parts. Bare conductors shall be securely and rigidly supported so that the minimum clearance between bare current-carrying metal parts of different voltages mounted on the same surface will not be less than 50 mm (2 in.), nor less than 25 mm (1 in.) for parts that are held free in the air. A clearance not less than 25 mm (1 in.) shall be secured between bare current-carrying metal parts and any metal surface. Adequate provisions shall be made for the expansion and contraction of busbars.

366.120 Marking.

1. Outdoors. Nonmetallic auxiliary gutters installed outdoors shall have the following markings:
   1. Suitable for exposure to sunlight
   2. Suitable for use in wet locations
   3. Installed conductor insulation temperature rating
2. Indoors. Nonmetallic auxiliary gutters installed indoors shall be marked with the installed conductor insulation temperature rating.