NEC 445.18 Disconnecting Means for Generators

[FaradayFF]

Greetings,

NEC 445.18 requires generators to be equipped with disconnects. Can a generator circuit breaker, if it is lockable in the open position, serve this purpose? I haven't seen separate disconnect switches supplied with standby generators on the past projects I've worked on.

Thanks,
EE

 

[tom baker]

Our WA state code rules allow a generator CB to be used and most of the generator CBs can have LO kit installed.

 

[iceworm]

445.18 was completely rewritten for 2017. I have not installed any generators under the 2017 code. I have not yet seen 2020 code.
Following is just my opinion. Yes, I have a lot of time with generators.
445.18.A and 445.18.B are intertwined. Should discuss together

445.18.A Disconnecting Means: My take is the CB/disconnect supplied with package unit generators meets the intent of 445.18.A. There is no requirement for the disconnect to be separate.

445.18.B Shutdown of Prime Mover: This one does require a separate shutdown (lockable? - maybe, probably) outside of the generator enclosure.
Considering normal installations 2017 code and earlier, generally not an issue.

Package generators with sheetmetal enclosures, controls mounted on the outside of the enclosures:​

A START key or a maintained, lockable E-STOP is sufficient. No change​

​

Generators with separate controls​

Controls inside building with generator​

A maintained lockable E-Stop located outside the generator building (enclosure) is required​

This one is really the only one that would have anything different or extra from 2017 code (and prior) installations. The normal Maintained, lockable STOP associated with the controls would have to have an additional Maintained, lockable E-STOP​

​

Controls in same building, but separate room​

A maintained lockable E-Stop located in controls room is required. No Change.​

 

[shortcircuit2]

2017 NEC...

445.18(A) disconnect needs provisions to lock.

445.18(B) prime mover shutdown is NOT required to be lockable, but qualifies as the 445.18(A) disconnect if it is lockable.

445.18(B) requires ALL generators to have a prime mover shutdown, and generators over 15KW to have an additional shutdown outside the equipment room or generator enclosure.

700.12(B)(6) requires the disconnect for outside generator sets to be within sight of building or structure supplied or an additional one must be provided at the building or structure.

From my research, the NEC drafted these rules from existing requirements in NFPA 110 section 5.6.5.6

 

[shortcircuit2]

2020 NEC...

Section 445.18 is restructured with basically the same rules except the added 445.18(D) provision...

445.18(D) 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 in a readily accessible location.

IMO...the Prime Mover Shutdown provision would satisfy this rule. I consider that it provided this Emergency Shutdown action under the 2017 rules. Being able to shutdown the generator set is a important safety provision for first responders so as to kill all power to a structure when necessary.

For 2020 the 445.18(D) Emergency Shutdown requirement for 1 & 2 family dwelling units coincides with the 230.85 Emergency Service Disconnect and the 706.15(A) ESS exterior shutdown requirement. But, IMO article 705 missed this provision.