Article 366 Auxiliary Gutters






Listing Requirements

If they are used outdoors they must be listed for use in wet locations, exposure to sunlight, and the maximum ambient temperature that they will be used in. If they are used indoors they must be listed for the maximum ambient temperature that they will be used in.

II. Installation


Uses Permitted

Auxiliary gutters can be used to supplement wiring spaces at meters, switchboards, and similar places as well as enclosed conductors or busbars.

  1. Sheet metal auxiliary gutters can be used outdoors or indoors. If they are installed in a wet location they must be suitable for a wet location.
  2. Nonmetallic auxiliary gutters have to be listed for the ambient temperature where they are being used and marked for the temperature rating of the conductor. If they are installed outdoors they must be listed and marked for that use. They can be used indoors.


Uses Not Permitted

They cannot be used to enclose equipment, switches, overcurrent devices, or similar equipment. They must not extend more than 9 m (30 ft.) from the equipment they supplement.


Number of Conductors

Not more than 30 conductors are allowed at any point without the derating factor of 310.15(B)(2)(a) and the area of the conductors cannot be more than 20% of the area of a sheet metal auxiliary gutter. For signaling or motor controller circuits where the conductors are used only for starting duty, they are not considered current carrying conductors. The area of the conductors in a nonmettalic auxiliary gutter cannot be more than 20% of the area of the gutter.


Ampacity of Conductors

The following refer to sheet metal auxiliary gutters. When there are not more than 30 current-carrying conductors, the derating factors for ampacities do not have to be applied. The capacities of bars cannot exceed 1.55 A per square millimeter (1000 A per square inch) for copper and 1.09 A per mm2 (700 A per square inch) for aluminum. For nonmetallic auxiliary gutters, use the derating factors in Section 310.15(B)(2)(a).


Securing and Supporting


Expansion Fittings


Splices and Taps


Insulated Conductors



Metal gutters must be grounded.

III. Construction Specifications





The following article titles are listed for reference:

Article 368Busways. Article 370Cablebus. Article 372Cellular Concrete Floor Raceways.

Article 90 Introduction


Wiring and Protection

Wiring Methods and Materials

Equipment for General Use

Special Occupancies

Special Equipment

Special Conditions


Annex C. Conduit and Tubing Fill Tables for Conductors and Fixture Wires of the Same Size

Annex D. Examples

Annex E. Types of Construction

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Pocket Guide to the National Electrical Code 2005
Pocket Guide to the National Electrical Code(R), 2005 Edition (8th Edition)
ISBN: 0131480014
EAN: 2147483647
Year: 2004
Pages: 120 © 2008-2017.
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