Code Change Summary: New code section on replacement panelboards.

In the 2023 NEC^®, language previously found in Section 408.8(A) was used to create new code section 408.9 which addresses replacement panelboards.

Keep in mind that panelboards are covered in NEC^® Article 408 while cabinets that enclose the panelboards are covered in NEC^® Article 312.

Sometimes it may be easier to remove and replace an obsolete panelboard and reuse the existing panelboard cabinet, especially when the cabinet is recessed into a wall.

Several manufacturers sell replacement retrofit panelboards that can be installed in an existing cabinet. The process typically involves providing measurements to the replacement panelboard manufacturer so they can provide the retrofit panelboard, as well as a new deadfront and panelboard cabinet cover. The defective or obsolete panelboard and circuit breakers can be removed and replaced with new components into the existing cabinet.

There are two distinctions to make regarding panelboards:

1. Underwriters Laboratories (UL) certifies (lists) panelboards without the enclosure. UL listed panelboards are certified using UL 67 which is the Standard for Safety for Panelboards.
2. UL also certifies panelboards with the enclosure which includes testing of the panelboard and the cabinet the panelboard is installed in. Enclosed Panelboards are certified using UL 67 and UL 50 or UL 50E (E for Environment in case the cabinet is used in wet, damp, corrosive, or other unique locations) which covers the testing of the panelboard cabinet.

When a panelboard without the enclosure is submitted for testing to a Nationally Recognized Testing Laboratory (NRTL) such as UL (as in item 1 above), the panelboard is tested to see if it complies with the requirements in UL 67, and no additional testing occurs related to any enclosure. These panelboards end up receiving a listing mark as a Listed “Panelboard”. Since the panelboard is not tested as a combination with a specific enclosure to see how the assembly contains arcs and sparks under short-circuit conditions with high available fault currents, a listed “Panelboard” is given a short-circuit current rating of not more than 10,000 amps.

When a panelboard with the enclosure is submitted for testing to a NRTL (as in item 2 above), the panelboard is tested to see if it complies with the requirements in UL 67, as well as the related requirements in UL 50 or UL 50E. These panelboards end up receiving a listing mark as a Listed “Enclosed Panelboard”.

Listed “Enclosed Panelboards” receive additional testing that Listed “Panelboards” do not. This testing can include adequate ventilation, sharp edges, wiring space, barriers, separation of circuits, the containment of arcs and sparks under short-circuit conditions, and the like. Enclosed panelboards are often tested to be able to contain arcs and sparks under high short-circuit current conditions and commonly have short-circuit current ratings significantly higher than 10,000 amps.

The differences in the required testing of Listed “Panelboards” versus Listed “Enclosed Panelboards” during the product certification process created the need for new code Section 408.9 to have separate requirements in subsections A and B.

The following is a summary of the new 2023 NEC^® code language in Section 408.9:

Panelboard replacements are permitted to be installed in existing enclosures in accordance with 408.9(A) or (B).

Section 408.9(A) is about Listed “Enclosed Panelboards”. If the replacement panelboard is listed for use with the existing specific enclosure (identified by either catalog number or dimensional information), the enclosed panelboard is permitted to maintain its original short-circuit current rating that is marked on the cabinet cover.

Section 408.9(B) is about Listed “Panelboards” that are not listed for use with a specific enclosure. If the available fault current where the retrofit panelboard is to be installed is greater than 10,000 amperes, the panelboard replacement will require a field evaluation by a Field Evaluation Body (as defined in Article 100) and must be field labeled. If the available fault current is 10,000 amperes or less, the replacement panelboard shall be identified for the application. Any previously applied listing marks on the cabinet that pertain to the panelboard must be removed.

Always determine the available fault current at the panelboard being replaced before the work is performed in order to ensure that the overcurrent devices in the new panelboard have an interrupting rating at least equal to the available fault current. This has been a requirement in Section 110.9 since the 1978 NEC^®. Compliance can also be achieved by using overcurrent devices that are part of a listed series rated system in accordance with 240.86.

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.