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Mike Holt's 2005 NEC Changes Summary
Articles 312 through 330
ARTICLE 312 Cabinets, Cutout Boxes, and Meter Socket Enclosures
This article addresses the installation and construction specifications for the items mentioned in its title. Why do we need a Code article telling us how to install these things? What can possibly go wrong? In Article 310, we observed that you need different ampacities for the same conductor, depending on conditions of use. The same thing applies to these items-just in a different way. For example, you can't use just any enclosure in a wet area or in a hazardous location. The conditions of use impose special requirements for these situations.
For all such enclosures, certain requirements apply-regardless of the use. For example, you must cover any openings, protect conductors from abrasion, and allow sufficient bending room for conductors.
Part I is where you'll find the requirements most useful to the electrician in the field. Part II applies to manufacturers. If you use name brand components that are listed or labeled, you do not need to be concerned with Part II. However, if you are specifying custom enclosures, you need to be familiar with these requirements to ensure the authority having jurisdiction approves the enclosures.
Part I. Installation
Article 314 - Outlet, Device, Pull and Junction Boxes, Conduit Bodies, and Handhole Enclosures
Article 314 contains installation requirements for outlet boxes, pull and junction boxes, conduit bodies, and handhole enclosures.
This is another article that can make you pause and ask, "What do we need this for?" It might seem there is no secret to installing a conduit body, fitting, or anything else mentioned in the title. But as with Article 312, conditions of use apply. If you're running raceway in a hazardous location, for example, you must use the correct fittings and the proper installation methods. But consider something as simple as a splice. It makes sense that you wouldn't put a splice in the middle of a raceway-doing so means you cannot get to it. But if you put a splice in a conduit body, you're fine, right? Not necessarily. Suppose that conduit body is a "short radius" version (think of it as an elbow with the bend chopped off). You do not have much room inside such an enclosure and for that reason; you cannot put a splice inside a short radius conduit body.Properly applying Article 314 means you will need to account for the internal volume of all boxes and fittings, and then determine the maximum wire fill. You'll also need to understand many other requirements, which we'll cover. If you start to get confused, take a break. Look carefully at the illustrations, and you'll learn more quickly and with greater retention.
Part I. Scope and General
The scope of Article 314 was expanded to include the requirements for handhole enclosures. See 314.30 for details.
Part II. Installation
Armored cable is an assembly of insulated conductors, 14 AWG through 1 AWG that are individually wrapped within waxed paper and contained within a flexible spiral metal sheath. Armored cable looks like flexible metal conduit.
Key point: The metal sheath serves as the effective ground-fault current path and there are no limitations to the number of bends between terminations.
Part II. Installation
ARTICLE 330 Metal-Clad Cable: Type MC
Metal-clad cable encloses one or more insulated conductors in a metal sheath of either corrugated or smooth copper or aluminum tubing, or spiral interlocked steel or aluminum. The physical characteristics of MC cable make it a versatile wiring method you can use in almost any location and for almost any application. The most common type of MC cable is interlocking type, which looks similar to armored cable or flexible metal conduit. Because the outer sheath of interlocking type cable isn't suitable as an effective ground-fault current path, it contains a separate equipment grounding (bonding) conductor.
Part III. Construction Specifications
Mike Holt's Comment: If you desire more information about any of the above changes, be sure to order my Changes book and/or library (Video/DVD).
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