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Are Type AC and Type MC cables considered pre-wired raceways?

Posted By Joseph Wages, Jr., Thursday, November 01, 2012
Updated: Tuesday, December 11, 2012

Question

Is the definition of a raceway applicable to Type AC cable and Type MC cable since these wiring methods are factory assembled with insulated conductors? Are Type AC cables and Type MC cables considered pre-wired raceways? KJ

Answer

This is an interesting question, and I appreciate an opportunity to address it. Let’s begin by looking at a few definitions. I am referencing the 2011 NEC for this information. A raceway is defined in Article 100 as an "enclosed channel of metal or nonmetallic material designed expressly for holding wires, cables, or busbars, with additional functions as permitted in the Code. Raceways include, but are not limited to, rigid metal conduit, rigid nonmetallic conduit, intermediate metal conduit, liquidtight flexible conduit, flexible metallic tubing, flexible metal conduit, electrical nonmetallic tubing, electrical metallic tubing, underfloor raceways, cellular concrete floor raceways, cellular metal floor raceways, surface raceways, wireways and busways.”

In Article 320, Type AC cable is defined as "a fabricated assembly of insulated conductors in a flexible interlocked metallic armor.” Looking closer at 320.100, it further states that "Type AC cable shall have an armor of flexible metal tape and shall have an internal bonding strip of copper or aluminum in intimate contact with the armor for its entire length.”

Article 330 defines Type MC (metal clad) cable as "a factory assembly of one or more insulated circuit conductors with or without optical fiber members enclosed in an armor of interlocking metal tape, or a smooth or corrugated metallic sheath.”

Article 300 will give us further guidance concerning a raceway as 300.18 tells us that "raceways, other than busways or exposed raceways having hinged or removable covers, shall be installed complete between outlet, junction, or splicing points prior to the installation of conductors.” This section further goes on to state that "prewired raceway assemblies shall be permitted only where specifically permitted in this Code for the applicable wiring method.”

I could not locate a definition for prewired raceway assemblies and feel that it does not apply to AC or MC cable. Article 354 covers Nonmetallic Underground Conduit with Conductors. This is known as Type NUCC. The definition states that this is "a factory assembly of conductors or cables inside a nonmetallic, smooth wall conduit with a circular cross section.” This item may fall under the nonexistent definition of a prewired factory assembly.

In conclusion, a raceway must be installed as a complete system before the routing or installation of conductors, which also provides for the removal of conductors. Cables are prewired assemblies whereby conductors cannot be installed or removed. Type AC cables and MC cables are not considered pre-wired raceways. They are fabricated assemblies of insulated conductors in a flexible metallic enclosure, interlocking metal tape, or a smooth or corrugated metallic sheath. —Joseph Wages, Jr. IAEI Alternate Rep CMP-3

Read more by Joseph Wages, Jr.

Tags:  Focus on the Code  November-December 2012 

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