Does armored fiber optic cable need to be grounded? Yes!

How to bond and ground

Understanding how to bond and ground a fiber-optic system with armored cable can be confusing. First, it is important to understand the difference between the terms bonding and grounding. According to the NEC and industry standards, bonding is the permanent connection of metallic parts to form an electrical path that will be conductive and continuous. Grounding is the act of connecting that path to the earth or some conducting body that serves as the earth. When all the components of a system are properly bonded together and grounded to the earth, the risk associated with electrical current harming personnel or damaging property and equipment is reduced.

The first step is to connect/bond the cable armor to a bonding or grounding electrode conductor. This can be accomplished right after the cable is accessed, and the armor is exposed. A bonding conductor or jumper is a short length of conductor, such as copper wire, that maintains electrical conductivity between two metal objects. The bonding conductor is required to be UL-listed and made of either copper or another corrosion-resistant conductive metal. This stranded or solid wire can be insulated, covered or bare. Most cable manufacturers supply an insulated, UL-listed 6-AWG copper strand. The 6-AWG size is preferred for the bonding conductor because that allows it to comply with both the NEC and ANSI-J-STD-607. The bonding conductor can be attached to the armor by the use of a listed clamp, lug or connector, as stated in NEC Article 250.70.

Once the clamp is installed, vinyl tape can be applied around the clamp and exposed armor to protect the installer and the fiber from any sharp edges where the armor is exposed.

grounding armored fiber

For the conductive fiber-optic cable to be fully grounded, the bonding conductor from the cable needs to be bonded to the intersystem bonding termination (if present), or another accessible location per NEC Article 770.100. The intersystem bonding termination is the device that connects the bonding conductors to the building’s grounding electrode and ultimately, to earth. Typically this is accomplished by connecting the bonding conductor to a dedicated path back to the telecommunications main grounding busbar (TMGB) or the telecommunications grounding busbar (TGB). The dedicated path can be a direct run or created by attaching to a rack or cabinet’s bonding system that bonds the rack or cabinet back to the TMGB or TGB. Specific requirements on how the TMGB or TGB are designed can be found in ANSI-J-STD-607 and other industry standards. When the armored cable is correctly bonded and grounded, it minimizes the risk of unwanted electrical current that could potentially harm personnel, property or equipment.

Props to Sara Chase with Corning Cable Systems.

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