Code Change Summary: New requirements were added to 408.6 requiring field marking, calculation, documentation, and verification of available fault current (AFC) and short-circuit current ratings (SCCR) for switchboards, switchgear, and panelboards.

SME commentary: In the 2026 NEC^®, Section 408.6 was reformatted into a list and expanded to include 5 line items for other than one- and two-family dwellings that dictate how available fault current (AFC) and short-circuit current rating (SCCR) requirements are to be applied to switchboards, switchgear, and panelboards. These revisions strengthen the link between 408.6 and the foundational rules in Sections 110.9, 110.10, 110.22, 110.24, and 240.86 by aligning marking, documentation, and recalculation procedures whenever changes occur that could affect available fault current levels.

Item (1) retains previous language and still requires the available fault current at the line terminals of the switchboard, switchgear, or panelboard and the date the calculation was performed to be field marked in a readily accessible location on the enclosure at the point of supply for other than one- and two-family dwellings.

A major addition is the new item (2), which requires field marking in a readily accessible location on the enclosure to indicate the short-circuit current rating of the equipment based on the OCPDs installed. This field marking enables installers, inspectors, and maintenance personnel to verify that the installed overcurrent protective devices (OCPDs) and the available fault current at the line terminals are properly aligned. The SCCR of a switchboard or panelboard is directly dependent on the OCPD protecting it. Some units contain an integral main circuit breaker (MCB) or main overcurrent device, while others are configured as main-lug-only (MLO) and supplied by an OCPD located elsewhere in the upstream equipment. The installer must first determine the AFC at the equipment location in accordance with NEC^® 110.9 and 110.10, and then select a switchboard or panelboard and OCPDs based on manufacturer literature to ensure that the protective device combination yields a sufficient SCCR.

Many switchboards and panelboards have several tested combinations of main and branch OCPDs that can achieve different SCCR levels. For example, if the AFC where a panelboard will be installed is 65,000 amperes (65 kA), and the manufacturer specifies that achieving this SCCR requires the use of a Type X main breaker with Type Y branch breakers, the selected combination must be field marked so future maintenance personnel know that the original installation was coordinated for that level of protection. If the OCPD types are later replaced with others that are incompatible with the existing field marked SCCR, the assembly could become underrated for the available fault current, creating a significant safety hazard. This level of marking clarity intends to ensure compliance with NEC^® 110.9 and 110.10 and prevent future misapplications.

A new item (4) now requires the available fault current calculation to be documented and made available to those authorized to inspect, install, or maintain the installation. This aligns with 110.24(A), 409.22(B), 430.99, and 440.10, emphasizing that having the AFC calculation documented is equally important for switchboards, switchgear, and panelboards as it is for service equipment, industrial control panels, motor control centers, and HVAC equipment.

Item (5) was added to require recalculation when system modifications occur that could change the available fault current, and a new last sentence before the informational note clarifies that if OCPDs are added or replaced, the interrupting rating of the replacement OCPDs shall be equal to or greater than the available fault current marked on the equipment in accordance with 408.6(1).

Finally, a new informational note directs code users to Section 110.22 for series combination systems, reinforcing that both protective coordination and series-rated combinations must be maintained after installation. Also see 240.86.

These comprehensive updates unify the relationship between AFC, SCCR, and field marking requirements across multiple NEC^® sections. By mandating documentation, verification, and accessible field markings, the 2026 NEC^® ensures that equipment ratings remain consistent with the available fault current throughout the life of the electrical system, greatly improving safety and accountability for installers, inspectors, and maintenance professionals.

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 2026 NEC^® edition of NFPA 70.

2023 Code Language:

408.6 Short-Circuit Current Rating. Switchboards, switchgear, and panelboards shall have a short-circuit current rating not less than the available fault current. In other than 1 & 2-family dwelling units, the available fault current and the date the calculation was performed shall be field marked on the enclosure at the point of supply. The marking shall be of sufficient durability to withstand the environment involved.

2026 Code Language:

408.6 Short-Circuit Current Rating. Switchboards, switchgear, and panelboards shall have a short-circuit current rating not less than the available fault current. In other than 1 & 2-family dwellings, switchboards, switchgear, and panelboards shall comply with the following, as applicable:

(1) The available fault current at the line terminals and the date the calculation was performed shall be field marked in a readily accessible location on the enclosure at the point of supply.

(2) The short-circuit current rating of switchboards and panelboards, at nominal circuit voltage, based on the OCPDs installed, shall be field marked in a readily accessible location on the enclosure.

(3) The marking required by 408.6(1) and 408.6(2) shall comply with 110.21(B).

(4) The available fault current calculation shall be documented and made available to those authorized to inspect, install, or maintain the installation.

(5) When modifications to the electrical installation occur that affect the available fault current at the line terminals of the equipment, the following shall apply:

a. The available fault current shall be verified or recalculated as necessary to ensure the equipment ratings are not less than the available fault current at the line terminals of the equipment.

b. The required field markings in 408.6(1) shall be adjusted to reflect the new level of available fault current.

When OCPDs are added or replaced, the interrupting rating of the replacement OCPDs shall be equal to or greater than the available fault current marked on the equipment in accordance with 408.6(1).

Informational Note: See 110.22 for series combination systems.