NEC Requirements for Generators | EC&M

The generator’s feeder neutral must be sized to carry the maximum unbalanced current as determined by Sec. 220.61. 

Disconnecting means and emergency shutdown

Generators, other than cord- and plug-connected portable generators, must have one or more disconnecting means capable of being locked in the open position per Sec. 110.25 [Sec. 445.18(A)].

A rule that’s new with the 2023 revision allows the disconnecting means to be located behind a hinged cover, door, or enclosure. Another new rule applies if the disconnect is located within the generator. In that case, a field-applied label conforming to Sec. 110.21(B) must be provided, and it must indicate the location of the generator disconnect.

Generators must have provisions to shut down the prime mover [445.19(A)]. The means of shutdown must comply with both 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 can satisfy the requirements of Sec. 445.18(A) if the shutdown device is capable of being locked in the open position per Sec. 110.25.

For other than one- and two-family dwelling units, generators with a rating greater than 15kW must have a remote emergency stop switch to shut down the prime mover [Sec. 445.19(B)]. The remote emergency stop switch must be outside the equipment room or generator enclosure and must also meet the requirements of Sec. 445.18(B)(1) and (B)(2). It can be mounted on the exterior of the generator enclosure.

For one- and two-family dwelling units, an emergency shutdown device must be located outside the dwelling unit at a readily accessible location [Sec. 445.19(C)]. Cord- and plug-connected portable generators are excluded from this requirement.

More to the job

Article 445 doesn’t cover everything you need to know for a Code-compliant generator installation. You must apply other Articles from Chapters 1 through 4. It gets tricky when you consider how to correctly apply Parts II and III of Art. 250 because the rules differ depending on the type of transfer equipment installed. For example, if your transfer switch switches the grounded conductor, the generator must be grounded as a separately derived system per Sec. 250.30. This topic could make for a multi-part article series.

These materials are provided by Mike Holt Enterprises in Leesburg, Fla. To view Code training materials offered by this company, visit www.mikeholt.com/code. 

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