Code Change Summary: New code section permits a metal enclosure to serve as an effective ground-fault current path.

There are several examples in Article 250 of metal boxes and other enclosures being part of the effective ground-fault current path but until now, Article 250 has never officially recognized it.

• NEC 250.110 requires enclosures of fixed equipment containing ungrounded conductors to be connected to an equipment grounding conductor.
• Part V of Article 250 requires bonding to ensure electrical continuity and the capacity of an enclosure to conduct safely any fault current likely to be imposed on it.
• Section 250.97 considers a metal raceway carrying a 277/480 circuit as properly bonded if it is connected to a box with listed fittings.

But what about the metal box itself? Is there any language in the NEC^® officially allowing a metal box or enclosure to be part of an effective ground-fault current path?

In the 2020 NEC^®, metal enclosures are now permitted to be used to connect bonding jumpers or equipment grounding conductors, or both, together to become a part of an effective ground-fault current path.

There were several similar public inputs (code change proposals) this cycle to recognize metal boxes and enclosures as an “equipment grounding conductor” by adding another line item to Section 250.118. This section provides a list of fourteen different items that are considered an “equipment grounding conductor”.

The new code language was placed in a new section and was worded carefully so as not to give the impression that a metal box or enclosure is technically an “equipment grounding conductor” since not all metal boxes or enclosures are listed as grounding and bonding equipment.

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.