General Grounding Question

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funky_gorilla

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CA
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Controls Eng.
Hello, I understand that a cable shield will need to be bonded and grounded, however I had a quick question regarding what will constitute bonded.

Currently we have a terminal block that is tied to the 120VAC ground of the system. If we wire in a cable shield to this grounding terminal block, are we able to consider this as "bonding"? Or would we need a separate busbar to tie into the grounding TB? This is a simple 120VAC system and we are looking to ground the armored shield of a fiber optic cable.
 
I had to look this up, I have installed a lot of non shielded fiber, so was not familiar with shielded fiber. The rules are in Art 770 Fiber Optic Cables, Part IV Grounding methods. You will need to run your grounding conductor to an intersystem bonding termination, lacking that terminal see section 770.100 B 3 and see IN figure 100.100 B 2.
This grounding/bonding connection is for protection from lightning and high voltage contact with the shield. Take a look at the IN 2 in 770.100 D
 
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One other comment, is this an outside plant fiber that is not listed to be inside a building? If so you are limited on how far past the point of entrance you can come into the building - thats 50 ft. See Section 770.48. I would come into the building with conduit, install a FO break out box, terminate the shield as above, and then run a jumper into your cabinet. If lightning or HV comes in contact with the shield, you don't want the energy getting into your control panel ground
 
Maybe being a bit picky, but since there are no conductors or other current carrying material inside the typical fiber optic cable it is misleading to call it shielded.
There may be a central steel core for strength in cable for aerial use or long pulls, and there may be a concentric metal layer to limit accidental low radius bending, provide cut and crush resistance, and reduce the effects of rodent damage.
To recognize this distinction, I would call it armored fiber rather than shielded fiber.
As a metallic connection entering the building it still needs to be bonded. The same would apply, IMHO to any central steel core.
 
Thank you gold digger. Looking back, I actually have terminated armored fiber cable, it was direct bury, the armor looked like MC cable armor. It was very difficult to cut the armor off. Non armored fiber is non conductive and can be run with power conductors.
 
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