Code Change Summary: The exception allowing an isolated metal elbow to remain ungrounded if at least 18 inches deep has been revised.

The previous wording in the 2014 NEC^® exception to 250.80 could be a bit misleading for those who like to play word games rather than install based on the intent of the code section.

The main rule for grounded electrical systems is to require all metal enclosures and raceways for service conductors and equipment to be connected to the grounded system conductor. The 2014 exception to the rule stated that a metal elbow, installed in an underground nonmetallic raceway, and isolated from possible contact by a minimum cover of 18 inches “to any part of the elbow” shall not be required to be connected to the grounded system conductor or grounding electrode conductor.

Technically, one could comply with the letter of the previous code language by installing the lowest part of a large pull elbow with at least 18 inches of cover while the upper portion of the pull elbow extends shallower or even above grade (see image).

The revised 2017 text makes it clear that the rule applies to all metal components (not just metal elbows) that are installed in a run of underground nonmetallic raceway. As well, the exception clears up the depth issue. Now, an isolated metal component can remain ungrounded if it has a minimum cover of 18 in. to all parts of the metal component.

A similar change occurred in 250.86 pertaining to isolated metal components used in underground runs of nonmetallic raceways, other than service raceways.

Below is a preview of Article 250. See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2017 NEC^® edition of NFPA 70.