Code Change Summary: New code sections to address selective coordination when replacements or modifications related to the emergency system occur.
In the 2023 NEC®, new requirements were added in 700.32 which address maintaining selective coordination and ensuring overcurrent protective devices (OCPDs) maintain their required selectivity when OCPD replacements or modifications occur related to the emergency system.
The existing code language in Section 700.32(A) still requires emergency system OCPDs to be selectively coordinated with all supply-side OCPDs but in the 2023 NEC®, the words “load-side” were added to make it clear that selective coordination must be examined both upstream and downstream.
Analyzing overcurrent device trip characteristics to determine if selective coordination can be achieved is not the job of the site electrician or the inspector. All too often, the inspector is asked by the site electrician for help in deciding how the adjustable settings on an OCPD should be set to achieve selective coordination since adjustments are typically preset to a default position by the factory when the OCPD is boxed up and sent to the job site.
Section 700.32(A) makes it clear that Selective coordination shall be selected by a licensed professional engineer or other qualified persons engaged primarily in the design, installation, or maintenance of electrical systems. The selection shall be documented and made available to those authorized to design, install, inspect, maintain, and operate the system.
In the 2014 NEC®, carefully chosen language was added to the Article 100 definition of Selective Coordination to make it clear that achieving selective coordination includes more than just picking the right overcurrent devices that are compatible for selective coordination. “Selection and installation” of the overcurrent devices is key. Part of installing them correctly is ensuring that any adjustable settings are properly set. Since adjustable overcurrent devices come from the factory with the settings dialed to the most restrictive condition, these adjustments must be properly set in the field according to the coordination study performed by the electrical engineer.
In the 2023 NEC®, there are two new requirements which require a careful read:
Even though the language in 700.32(B) and (C) above is triggered by replacing an OCPD in the “emergency system” or a modification, addition, or deletion “to the emergency system”, selective coordination should be reevaluated any time a replacement or modification occurs related to any overcurrent device that could impact the emergency system to comply with the new language in Section 240.11.
It would be a violation of 240.11 to replace an adjustable trip circuit breaker (not technically part of the emergency system) downstream of a service OCPD with no regard to maintaining existing selectivity in an installation where an emergency system feeder OCPD is required to be selectively coordinated with the same service OCPD.
A similar code change occurred in 701.32 for selective coordination in legally required standby systems.
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:
The language in Sections 700.32(B) and (C) did not exist.
2023 Code Language:
700.32 Selective Coordination.
N (B) Replacements. Where emergency system(s) OCPDs are replaced, they shall be reevaluated to ensure selective coordination is maintained with all supply-side and load-side OCPDs.
N (C) Modifications. If modifications, additions, or deletions to the emergency system(s) occur, selective coordination of the emergency system(s) OCPDs with all supply-side and load-side OCPDs shall be reevaluated.
Based on the 2023 NEC, which of the following is true?
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