Motor and Generator Institute has received several questions from students regarding proper placement of the remote manual stop station for an emergency power supply (EPS) located outside with an enclosure. Some have stated the manual stop station must be located in a “remote” location some distance away from the enclosure, while others have stated, there is no specific location stated other than “outside” the room housing the prime mover. Motor and Generator Institute recently contacted CMS for interpretation.
Question: “Is the CMS now disallowing remote manual stop stations from being located on the outside of a generator enclosure, located outside of a building?”
Answer: “CMS’s long-standing interpretation is that a manual stop needs to be “remote” from the generator as prescribed by 2010 NFPA 110, 22.214.171.124. As such, to be “remote,” a manual stop could not be located on the generator housing.”
The CMS adopted NFPA 99, Health Care Facilities Code, and NFPA 101, Life Safety Code, 2012 edition in 2017. Both reference NFPA 110, Emergency and Standby Power Systems, 2010 edition.
NFPA 110, 2010 Edition
126.96.36.199* All installations shall have a remote manual stop station of a type to prevent inadvertent or unintentional operation located outside the room housing the prime mover, where so installed, or elsewhere on the premises where the prime mover is located outside the building.
188.8.131.52.1 The remote manual stop station shall be labeled.
As you can imagine there are several implications and possible conflicts, especially since emergency stop switches have been placed on the outside of generator enclosures since the 80s. With the release of the National Fire Protection Association (NFPA) 110, 2019 Edition, the above reference was modified.
NFPA 110, 2019 Edition
184.108.40.206 All installations shall be provided with at least one remote emergency stop switch for each prime mover.
220.127.116.11.1 The remote emergency stop switch shall be located outside the room housing the prime mover or exterior enclosure and shall be permitted to be mounted on the exterior of the enclosure.
18.104.22.168.2 Provisions shall be made so access is limited to qualified persons.
22.214.171.124.3 The remote emergency stop switch shall identify the prime mover it controls.
Also NFPA 70, 2017 Edition states:
445.18 Disconnecting Means and Shutdown of Prime Mover.
(A) Disconnecting Means. Generators other than cord-and-plug-connected portable shall have one or more disconnecting means. Each disconnecting means shall simultaneously open all associated ungrounded conductors. Each disconnecting means shall be lockable in the open position in accordance with 110.25.
(B) Shutdown of Prime Mover. 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
Generators with greater than 15kW rating shall be provided with an additional requirement to shut down the prime mover. This additional shutdown means shall be located outside the equipment room or generator enclosure and shall also meet the requirements of 445.18(B)(1) and (B)(2).
(C) Generator Installed in Parallel. Where a generator is installed in parallel with other generators, the provisions of 445.18(A) shall be capable of isolating the generator output terminals from the paralleling equipment. The disconnecting means shall not be required to be located at the generator.
As you can see the latest edition of NFPA 70 (NEC®) calls for the remote stop station to be “located outside the equipment room or generator enclosure” and the latest edition of NFPA 110 states “outside the room housing the prime mover or exterior enclosure and shall be permitted to be mounted on the exterior of the enclosure.” With generators located outside in weatherproof enclosures, there seems to be confusion on compliant locations.
MGI would like your comments as we plan to continue discussions with the CMS.