Where are you getting 3ft length? Stipulations that GEC be in some form of protection is found in as Roger stated in 250.64(B) particularly (B)(2) if exposed to physical damage, but it is not limited to EMT can be RMC, IMC, PVC, RTRC-XW, or even cable armor. But even there, no reference to 3ft.
That’s why I always use pvc! Also don’t use metal mineralac straps, as they cause a “choke” effect according to Verizon’s engineers.
Do you understand what ferrous means? If not, I suggest you find out. You can answer the question yourself.
It is. Look up the definition it is a substantial part of several code sections.
my guess is whatever "choke" effect there might be really does not matter much in the grand scheme of things. If you get hit by lightning, I doubt that having the GEC bonded to whatever ferrous metal might surround it will make any difference.
Do you also use plastic locknuts?
No TA or locknuts, it is just a sleeve protecting the GEC, it does not have to be terminated at either end.
Just what an engineer told me at a Verizon switching station. He wanted either a two hole metal strap, or a pvc strap, but no metal completely encompassing the pvc.
It does make a difference to bond the GEC to each end of the metallic raceway enclosing it. Since lightning is high frequency it travels more on the surface and the raceway having a larger surface area decreases the impedance. It’s the same reason why a flat copper strip is used instead of a wire. My source on bonding a metal race way is the IEEE green book.
I don't doubt that it is "better". I doubt it matters all that much one way or the other.
While it exists in nonferrous, that is fairly rare, and other than at a trade show, I have never seen the nonferrous version.
