PI: 240.4 (First)

[wwhitney]

A couple technical corrections so the literal meaning of the section matches the common understanding.

Cheers, Wayne


240.4 Protection of Conductors Circuit conductors, other than flexible cords, flexible cables, and fixture wires, shall be protected against overcurrent in accordance with their ampacities specified in 310.14, unless otherwise permitted or required in 240.4(A) through (H).

Statement of Problem and Substantiation for Public Input

Overcurrent devices are not installed in equipment grounding conductors and other conductors that are not part of a circuit. So while obvious, that distinction should be made explicit.

 

[tortuga]

I say an EGC is indirectly protected by circuits OCPD, thats why 250.122 references a OCPD.

 

[wwhitney]

I say an EGC is indirectly protected by circuits OCPD, thats why 250.122 references a OCPD.

OK, but I don't see that statement as being at odds with either the PI or the substantiation. EGCs definitely aren't "protected against overcurrent in accordance with their ampacity."

Cheers, Wayne

 

[LarryFine]

EGCs definitely aren't "protected against overcurrent in accordance with their ampacity."

That's because of the short duration of (most) direct-to-grounded-parts faults.

 

[wwhitney]

That's because of the short duration of (most) direct-to-grounded-parts faults.

I agree. But the point of the thread and PI is that read strictly, 240.4 would currently require EGCs to be "protected against overcurrent in accordance with their ampacity." Because it applies to all "conductors," and EGCs are conductors.

Does the substantiation need rewriting because I haven't explained that?

Cheers, Wayne

 

[yesterlectric]

I personally don’t think this clarification is necessary although I guess it won’t hurt if they take the time to debate it and put it in. The only thing it would hurt is that the NEC keeps getting to be a larger and larger volume and in many cases full of hastily generated conflicted language. And NFPA is trying to hide this by just increasingly shrinking the font in their books even as the average age of the electrician continues to increase. This change however would hardly fall into that category.

Hopefully anyone who’s qualified to actually do work understands well that you wouldn’t fuse an equipment ground as you may as well forget any overcurrent protection if you did so.

Are we going to add a clarification also to make it clear that when EMT conduit is used as the equipment grounding conductor, that it doesn’t need to be on an overcurrent protection device? Or what about metallic parts like a building frame that likely will conduct full current even though it’s not necessarily intentional? Do we need to clarify that you don’t need to add an insulator between beams, then include a jumper with a fuse in between two metal parts that are bolted together?

 

[wwhitney]

I personally don’t think this clarification is necessary although I guess it won’t hurt if they take the time to debate it and put it in. The only thing it would hurt is that the NEC keeps getting to be a larger and larger volume and in many cases full of hastily generated conflicted language.

This PI is the opposite of "hastily generated conflicted language." This PI is about adjusting the language to actually say what is intended. And EGCs are not intended to be "protected against overcurrent in accordance with their ampacities."

Cheers, Wayne