Isolated Structural Steel

[Dennis Alwon]

Someone can start a survey and see how many people have seen wires that were fraid and energized the steel or metal where it was in contact. I did get knock on my butt touching a flex metal duct under a house once but I am not sure where the problem was as the furnace & wiring got replace and problem went away. Old wiring no ground etc.....

I am not certain I have every seen an energized beam.

 

[don_resqcapt19]

With all due respect to Mr. Sargent, if the term is not defined in the NEC itself, there is nothing that tells us that we should look to the NEC Style Manual for a definition.
Yes, the term likely to become energized is listed in Annex B as a "standard term", Section 3.2.1 of the NEC Style Manual says:

3.2.1 Unenforceable Terms. The NEC shall not contain references or requirements that are unenforceable or vague. The terms contained in Table 3.2.1 shall be reviewed in context, and, if the resulting requirement is unenforceable or vague, the term shall not be used.

Table 3.2.1 lists terms that are "possibly unenforceable and vague". The word "likely" is found in this table.

likely to become energized -- failure of insulation on

Even with that in the style manual, it still hinges on what is "likely". Give the relatively few cases of insulation failures as compared to the total number of electrical installations, I conclude that insulation failure is not likely....sure it is possible and it does happen, but it is not likely.

 

[Smart $]

I would surely hate to bond every truss together in the entire building.

Standard trusses stand alone, not sure about metal trusses.

Structurally, I don't believe there to be any truss system that does not require cross bracing, which is typically done with the same material and fasteneing means as the truss members.

My reference to a portion of a building frame was regarding the framework being electrically isolated (i.e. lacking an effective fault-current path path) from the building's electrical system. And in determining such, it seems the NEC ignores any grounding that occurs through attachment of metal conduit or metallic-sheathed cable.