National Electrical Installation Standards

Standards as High as Your Own

Thursday, November 2, 2017


In definitions of 517 for “Essential Electrical System” and “Critical Branch” and “Life Safety Branch” it is clear that parts of these systems include Feeders and Branch circuits. In my mind I see this not only from the service disconnecting means bout also from the alternate source of power ie: generator. In section 517.30(C)(3) under “Mechanical Protection…”. In number (1) of this section if PVC is used Schedule 80 is required. In Number 2 of this section if schedule 40 PVC is used it shall be encased in 2” of concrete.

Q- Would this requirement be from the alternate source ie: Generator all the way to the building (ie: underground installation) / the branch circuit Panel Board?


Lukas Koomen



Hey Lukas thanks for your question. The rules for mechanical protection of the essential electrical system wiring are now in 517.31(C)((3)  in the 2017 NEC. Yes, this rule applies to all the wiring regardless of its location to its source.

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