Roger, how would putting it in pipe help with spec's. Does it decrease overall impedance of the length of wire when done in pipe and properly bonded, or is this just something you normally see in hospitals and sensitive electronics labs.
I've never seen it done in my day like that in all the machine shops and commercial buildings I've seen.
But if it helps in overall performance, it is something I'd like to rethink and do.
Any more info you have on this application is appreciated.
Dnk, specs are not always for performance, alot of the times I see this in specs, it is basically for neatness or asthetics.
Now as far as performance is concerned, let's take the "Choke Effect" out of the conversation, and think parallel conductor.
When the metallic raceway and GEC are bonded together at both ends they become a parallel conductor reducing the resistance and impedance of the path, so with this in mind, it would make sense to bond the raceway and conductor regardless of any other considerations.
DNK, what you are asking is answered "4 ga or larger does not *normally* require physical protection". 250.64(B) ...A 4 AWG copper or aluminum or larger conductor shall be protected if exposed to severe physical damage.
What is "severe"? Ask your AJH what it is that day.