My question actually concerns a telecommunications bonding backbone (TBB) and/or the branch(es) that land on telecom equipment. However, the way it is handled per ANSI/TUA/EIA-607, the TBB is similar to the GEC on the way it is dealt with in the NEC. Both ends of a ferrous conduit must be bonded to avoid the potential of a choking effect. I will give sinarios followed by my opinion.
1) GEC exits the side of a main service panel, through a chase nipple (or Romex connector), and lands on a steel beam next to the service. No bond bushing/wedge is required.
2) GEC exits the bottom of the main service, through a chase nipple, directly into a steel gutter/trough mounted to the panel. It then continues through another chase nipple before making its way outside to a ground rod. A gutter/trough is not defined as a conduit but does it essentially act as one with the cover on? I still say, no bond bushing/wedge(s) is/are needed.
3) Take the #2 sinario, but instead of using a chase nipple, cut out the bottom of the main panel (leaving just a 3/4" flange around the outside) and bolt it directly to the top of the gutter with a matching hole. The panel and gutter are now, essentially, the same, oddly-shaped box. If #1 did not require a bond bushing then #3 definitely does not either.
4) Again, take sinario #2 but gradually increase the length of the conduit connecting the panel and the gutter. Go from a chase, to a close, to a short nipple (and beyond). At what point is/are bond bushings needed? Also, is the length of gutter ever a determining factor? Since my question actually is for a TBB (and its branches) not a GEC, the ANSI/TIA/EIA-607 rule is that the ferrous "conduit" cannot be longer than 3' without requiring bond bushings. Do I count the total length of wire from where it exits the panel to where it exits the steel gutter in 1, 2, and 4 above?
I understand that IT equipment is typically bonded by a #6 landed on the OUTSIDE of the cabinet, but the layout of the room may make this less than a clean install. Thanks for reading this far.
