6 Oct 2016
What’s the Difference Between AC and MC Cables?
The current construction of Armored Cables (Type AC) that is approved by UL® 4, has an aluminum bonding wire in contact with the metal armor that provides a low-impedance ground path that is required for the proper operation of overcurrent protection devices. This style cable was in use for many years before the introduction of Metal Clad Cables (Type MC).
Traditional Metal Clad Cables utilize one or more green copper grounding conductors and the armor is not an approved equipment grounding means. This is one of the major differences between the two styles of cable. In addition, Type MC Cables also utilize a polypropylene assembly tape rather than the Kraft paper tape on individual conductors that is used on traditional Type AC cables.
As technology advanced, so too did the construction of Metal Clad Cables. Over the years, contractors realized the benefits to using Type MC cable versus Type AC, however, the need for the armor to be an approved equipment ground still persisted.
The birth of MCI-A Style Cables
In the late 2000’s, a new style of Type MC Cable was designed that incorporated full-sized bare aluminum ground wire plus the armor as the equipment grounding means. This cable was referred to as Type MCI-A, referencing the style of fitting needed in order to ensure the bonding wire was properly installed. The MCI-A cables are the ideal fit for a contractor that prefers Type MC Cables with the benefit of the armor/ bond wire ground path. An additional benefit of MC Cables is that you are not limited to the number of conductors within the armor. Per UL® 4, AC cables may only have a maximum of four circuits, whereas this limitation does not apply to MC Cables.
Special attention should be paid to terminating Type MCI-A cables as the aluminum bonding wire must maintain contact with the armor upon termination. There are several ways to do this, as noted by AFC Cable Systems® installation instructions. MCI-A style cables are now common in the electrical industry and also come in healthcare facility (HCF) versions.
AFC Cable Systems® introduced their Type MCI-A style cables in 2012, MC-Quik® Cable and MC-Stat® Cable for healthcare. In addition to the armor/ bond wire ground path, AFC also provides labor savings to the contractor by eliminating the overall polypropylene assembly tape, instead a protective covering is extruded directly onto each individual conductor. Removing the overall tape eliminates the time to remove it to access the conductors and eliminates the waste of the scrap.
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