ECN Forum Forums Code Related Discussion NEC & other Code issues Metal Clad Cable

What is the best way to determine if the sheath of metal clad cable is suitable for equipment grounding. (Frank) cinkerf

Go to http://www.afcweb.com./ and enroll in their online learning program. It doesn't take long. AFC manufactures MC cable.

It looks to me that MC armor by itself is not approved for Grounding. But AC armor w/strip is.

Table at: http://www.afcweb.com./groundcp.html

I located section 250.18(8)(11) "The metallic sheath OR the combined metallic sheath and grounding conductors of type MC cable". It falls under Types of Equipment Grounding Conductors. If read word for word it seems as if the sheath of MC cable would be suitable for an equipment grounding method. (Frank) cinkerf

Correction. That is section 250.118(8)(11)

Frank,

You got me wondering what's going on then. If you look at AFC's FAQ page it lists some Qualities of the MC cable types


"The difference between HCF and MC cables (as manufactured by AFC Cable Systems) is the grounding capabilities of the cable assemblies.

Type HCF cable has a green grounding conductor plus the armor/bond wire combination, thereby providing redundant or isolated grounding capability. HCF is a Type AC cable and is manufactured in accordance with U.L. 4.

HCF cable may be installed in compliance with NEC 517 for health care facilities.

Type MC has only one equipment grounding means, a green grounding conductor. There are types of MC cable manufactured by AFC with two grounding conductors for additional grounding capability."

This is from page: http://www.afcweb.com./faq.html
and would seem to indicate that it is not approved for Grounding. I can see why you're questioning it.

The UL White Book indicates that the interlocked metal tape sheath is NOT suitable as a grounding conductor and an insulated or bare EGC will be provided. It also says that "the sheath of the smooth or corrugated tube Type MC calbe or a combination of the sheath and a supplemental bare or green insulated conductor is suitable for use as the required EGC".
Don(resqcapt19)

Don,
In the margin of section 250.118(8)(11) there is a verticle line which indicates a code change from the previous (1996) NEC. It does not specify smooth or interlocked metal sheath. It simply states type MC cable. I would have to agree with you based on your findings in the UL White Book.
(Frank) cinkerf