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Grounding of Armored Fiber Optic Cables

National Electrical Code 2008 covers the grounding or interruption of non-current-carrying metallic members of optical fiber cables.

The grounding rules are defined for outside or inside of a building. The main rule is defined in NEC section 770.100 – Entrance Cable Grounding.

Entrance Cable Grounding

Grounding conductor needs to be insulated, made of copper (or other corrosion resistant material), and stranded or solid.

The size must be no smaller than 14 AWG and having an ampacity equal or larger than the conductive elements of the cable assembly, but it doesn’t need to be larger than 6 AWG.

It must be run in as straight a line as possible, and be guarded from physical damage. If run in a metal raceway, both ends must be bonded.

Electrode terminations are also covered. If an intersystem bonding terminations exist, then the termination should be to that point. If there is no intersystem bonding point, but there are grounding electrodes, then the connection must be made to that grounding system.

If the building has no intersystem bonding termination and no grounding electrode system, then you can ground to the nearest building electrodes such as water pipe, building steel, ground ring, etc.

If you cannot find all the above, then the grounding should be done to a 5 feet ground rod which is driven into permanently damp soil.

The electrode, although required to be at least 6 feet from other electrodes, must be bonded to the power system grounding with no smaller than 6 AWG copper conductor.

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