445.18 & 19 Disconnecting Means and Emergency Shutdown of Prime Mover.
Code Change Summary: The disconnection and emergency shutdown requirements for generators have been revised and reorganized.
In the 2023 NEC®, the rules on emergency shutdown of a generator prime mover (previously in Section 445.18) have been moved to new Section 445.19 to separate the generator emergency shutdown requirements from the generator disconnect requirements still located in Section 445.18.
Section 445.18 now provides requirements only for the generator disconnect. This section requires generators (other than cord-and-plug-connected portable generators) to have one or more disconnecting means. Each disconnecting means must open all associated ungrounded conductors simultaneously. Each disconnecting means must also be lockable in the open position in accordance with Section 110.25.
Additionally, the 2023 NEC® brings a new provision in Section 445.18 that allows a generator disconnecting means to be located within the generator behind a hinged cover, door, or enclosure panel with field labeling to identify its location.
Some electrical inspectors were enforcing a literal interpretation of the code language in Section 702.12(A) and thought that the actual handle of the generator disconnecting means was required to be within sight of the building or structure supplied, and required additional safety switches where a circuit breaker type disconnecting means was within the generator assembly behind a cover.
In 2023 NEC® Section 445.18(A), if the generator disconnecting means is located within the generator, a field applied label that meets the requirements in Section 110.21(B) must be provided indicating the location of the generator disconnecting means.
The new labeling requirement does not specify where exactly the label must be applied at the generator, but affixing the label to the generator enclosure in a conspicuous place helps first responders searching for the generator disconnect if they intend to terminate all power to the premises as part of their operation.
One of the changes in new Section 445.19(B), which covers remote emergency shutdown is the exclusion of one- and two-family dwelling units from the requirement. In the 2020 NEC® this language was in Section 445.18(C) and applied to remote emergency shutdown of the prime mover for any generator rated greater than 15kW regardless of occupancy type. In the 2023 NEC®, Section 445.19(B) requires a remote emergency stop switch for generators rated more than 15kW in other than one- and two-family dwelling units.
Both the remote emergency stop switch specified in 445.19(B) and the emergency shutdown device in 445.19(C) must be labeled “Generator Emergency Shutdown”, and the label must meet the requirements of Section 110.21(B).
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.
2023 Code Language:
445.18(A) Disconnecting Means. Generators other than cord-and-plug-connected portable generators shall have one or more disconnecting means. Each disconnecting means shall simultaneously open all associated ungrounded conductors. Each disconnecting means shall be lockable open in accordance with 110.25.
The disconnecting means shall be permitted to be located within the generator behind a hinged cover, door, or enclosure panel. Where the generator disconnecting means is located within the generator, a field applied label meeting the requirements of 110.21(B) shall be provided indicating the location of the generator disconnecting means.
N 445.19(A) General. Generators shall have provisions to shut down the prime mover. The means of shutdown shall comply with all of the following:
(1) Be equipped with provisions to disable all prime mover start control circuits to render the prime mover incapable of starting
(2) Initiate a shutdown mechanism that requires a mechanical reset
The provisions to shut down the prime mover shall be permitted to satisfy the requirements of 445.18(A) where it is capable of being locked in the open position in accordance with 110.25.
N 445.19(B) Remote Emergency Shutdown. For other than one- and two-family dwelling units, generators with greater than 15 kW rating shall be provided with a remote emergency stop switch to shut down the prime mover. The remote emergency stop switch shall be located outside the equipment room or generator enclosure at a readily accessible location and shall also meet the requirements of 445.19(A)(1) and (A)(2).
The remote emergency stop switch shall be permitted to be mounted on the exterior of the generator enclosure. The remote emergency stop switch shall be labeled Generator Emergency Shutdown, and the label shall meet the requirements of 110.21(B).
N 445.19(C) Emergency Shutdown in One- and Two-Family Dwelling Units. For other than cord-and-plug-connected portable generators, an emergency shutdown device shall be located outside the dwelling unit at a readily accessible location and shall also meet the requirements of 445.19(A)(1) and (A)(2).
An emergency shutdown device mounted on the exterior of the generator enclosure shall be permitted to satisfy the requirements of this section. The shutdown device shall be marked as the Generator Emergency Shutdown, and the label shall meet the requirements of 110.21(B).