250.148 Continuity and Attachment of Equipment Grounding Conductors to Boxes.

A wire type equipment grounding conductor of a circuit passing through the box is not required to be connected to the box.
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A wire type equipment grounding conductor of a circuit passing through the box is not required to be connected to the box.

Code Change Summary: Clarifications were made regarding the connection of equipment grounding conductors in a box.

When conductors are spliced inside a box or terminated to equipment in/connected to the box, the equipment grounding conductors for those circuits must connect to the metal box. The 2014 language in this section was a bit misleading and did not best represent what the code section was intending to accomplish.

The previous wording required “any” equipment grounding conductor to be connected to the box. In the 2017 NEC®, “all” equipment grounding conductors of circuits spliced inside the box need to be connected to the box.

Sometimes, a box may contain several different sized circuits, each requiring a specific sized equipment grounding conductor. The old code language, if misapplied, could allow just one of the equipment grounding conductors to make connection to the box; possibly even the smallest equipment grounding conductor inside the box. This would render the box insufficiently grounded in the event that the largest circuit in the box faulted and energized the metal box.

Requiring the equipment grounding conductors of all spliced circuits in a box to be connected to the metal box ensures that a metal box with several different sized equipment grounding conductors will be properly grounded for the largest fault condition likely to be imposed on the box.

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.

2014 Code Language:

250.148 Continuity and Attachment of Equipment Grounding Conductors to Boxes. Where circuit conductors are spliced within a box, or terminated on equipment within or supported by a box, any equipment grounding conductor(s) associated with those circuit conductors shall be connected within the box or to the box with devices suitable for the use in accordance with 250.148(A) through (E).

2017 Code Language:

250.148 Continuity and Attachment of Equipment Grounding Conductors to Boxes. If circuit conductors are spliced within a box or terminated on equipment within or supported by a box, all equipment grounding conductor(s) associated with any of those circuit conductors shall be connected within the box or to the box with devices suitable for the use in accordance with 250.8 and 250.148(A) through (E).

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250.148 Continuity and Attachment of Equipment Grounding Conductors to Boxes.

Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:

Which of the following is true when installing circuits inside a junction box?

A: If circuits are present inside a plastic box, the equipment grounding conductors associated with those circuits must be connected to the box.
B: If circuits are present inside a plastic box, the box must be grounded.
C: If circuits are spliced inside a metal box, the equipment grounding conductors associated with those circuits must be connected to the box.
D: Conductors being pulled through a plastic box without a splice must be connected to the box.
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