408.38 Enclosure.

This enclosed panelboard has a short-circuit current rating of up to 100kA and can be installed at a point in the electrical system where the available fault current is higher than 10kA in compliance with NEC 110.9, 110.10, 408.6, and 408.38.
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This enclosed panelboard has a short-circuit current rating of up to 100kA and can be installed at a point in the electrical system where the available fault current is higher than 10kA in compliance with NEC 110.9, 110.10, 408.6, and 408.38.

Code Change Summary: New requirements added to address the evaluation of panelboards and enclosures as a combination.

In the 2023 NEC®, A sentence derived from the UL 67 Standard for Panelboards was added to Section 408.38 which provides insight on the evaluation of panelboards with specific enclosures for installations where the available fault current is greater than 10,000 amps.

Section 25.1.1 of UL 67 states that “Panelboards” (not provided with an enclosure) shall be rated 10,000 amps maximum, unless they are marked for use with a specific enclosure as noted in 34.12.9.

Panelboards with a short-circuit rating higher than 10,000 amps are tested in combination with a specific enclosure and listed as an “Enclosed Panelboard”. Additional testing occurs for listed “Enclosed Panelboards” that does not occur for listed “Panelboards” including the containment of arcs and sparks under short-circuit conditions where the available fault current can exceed 10,000 amps. It would be a violation to take a listed “panelboard” and fit it into a cabinet (without proper evaluation as a combination) if the installation was at a location in the electrical system where the available fault current is higher than 10,000 amps.

The short-circuit current rating of a listed “Enclosed Panelboard” is marked on the listed equipment so that the electrician can determine the available fault current at the point in the electrical system where the enclosed panelboard is to be installed and then select an enclosed panelboard with the proper short-circuit current rating in compliance with NEC® Section 110.10 which has been in the NEC® since 1965, and Section 408.6 which was added in 2020.

In the 2023 NEC®, the code change in Section 408.38 makes it clear that if a panelboard is to be installed in a location of the electrical system where the available fault current is greater than 10,000 amperes, the panelboard and enclosure combination shall be evaluated for the application.

The NEC® has no definition of “evaluated” in Article 100, but Section 110.3(C) makes it clear that product testing, evaluation, and listing (product certification) shall be performed by recognized qualified electrical testing laboratories in accordance with applicable product standards. See also Section 90.7 where the authority having jurisdiction is permitted to base their approval on equipment evaluated and listed by a qualified electrical testing laboratory.

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 2023 NEC® edition of NFPA 70.

2020 Code Language:

408.38 Enclosure. Panelboards shall be mounted in cabinets, cutout boxes, or identified enclosures and shall be dead-front.

2023 Code Language:

408.38 Enclosure. Panelboards shall be mounted in cabinets, cutout boxes, or identified enclosures and shall be dead-front. Where the available fault current is greater than 10,000 amperes, the panelboard and enclosure combination shall be evaluated for the application.

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408.38 Enclosure.

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

Based on the 2023 NEC, which of the following is true?

A: If a panelboard is to be installed in a location of the electrical system where the available fault current is greater than 10,000 amperes, the panelboard and enclosure combination shall be evaluated for the application.
B: If a panelboard is to be installed where the available fault current is 1000 amperes, the panelboard and enclosure combination shall be third party inspected.
C: A panelboard installed where the available fault current is 100,000 amperes must be listed as a “Panelboard”.
D: Panelboards are NOT permitted to be installed where the available fault current exceeds 100 amps.
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