Code Change Summary: Revised code language now includes bonding requirements for cable armor.

NEC Section 210.64(E) provides requirements for ferrous metal raceways and enclosures that contain a grounding electrode conductor. Ferrous metals contain appreciable amounts of iron such as steel and are usually magnetic. A non-ferrous metal does not have magnetic properties and includes metals such as aluminum and copper.

The general rule for ferrous metal raceways and enclosures containing a grounding electrode conductor requires them to be electrically continuous from the point of attachment to cabinets or equipment to the grounding electrode and to be securely fastened to the ground clamp or fitting.

In the 2020 NEC^®, cable armor must now comply with this section. Cable armor is similar to armored cable type AC, but there is little space between the armor and the conductor inside. The NEC^® does not have a specific article covering cable armor. Most cable armor is made of a ferrous galvanized steel interlocking armor applied over a bare conductor (see image).

The revised code language requires ferrous metal raceways, enclosures, and cable armor to be bonded at each end of the raceway or enclosure to the grounding electrode or grounding electrode conductor to create an electrically parallel path. Bonding methods permitted to accomplish this include the following three methods from Section 250.92(B)(2) through (4):

• Connections using threaded couplings or listed threaded hubs on enclosures if made up wrenchtight
• Threadless couplings and connectors if made up tight for metal raceways and metal-clad cables
• Other listed devices, such as bonding-type locknuts, bushings, or bushings with bonding jumpers

There are currently fittings that can be used to bond the cable armor to the service enclosure, but it will be interesting to see what methods will be used at the other end to bond the cable armor to the actual grounding electrode.

Below is a preview of the NEC^®. See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2020 NEC^® edition of NFPA 70.