Guide to Network Cabling Fundamentals Chapter 2

Chapter 2 - Grounding and Bonding Discuss how grounding and bonding work Differentiate between “grounding and bonding systems” and “grounding and bonding equipment” Understand cable protection and equipment-grounding practices Identify the three types of telecommunications circuit protectors Understand how documentation helps you and your network

A Closer Look at Grounding and Bonding Standards from the following organizations are the four main sources for information about grounding and bonding codes and practices National Electrical Code (NEC) ANSI/EIA/TIA-607: Commercial Building Grounding and Bonding for Telecommunications Underwriters Laboratories UL-497: Protectors for Paired Conductor Communication Circuits IEEE Standard 142-1991: Grounding of Industrial and Commercial Power Systems

A Closer Look at Grounding and Bonding Grounding, Bonding, and Effective Ground: A ground is a conducting connection between an electrical circuit and the earth, or a conducting body Bonding is the permanent joining of metallic parts to form a conductive path that ensures electrical continuity and safely conducts current An effective ground is an intentional connection to a low-resistance earth ground that permits current to discharge into the earth without buildup of hazardous voltages on the cable, equipment, or people

A Closer Look at Grounding and Bonding Grounding and bonding network components: When designed and installed following the appropriate codes, specifications, and safety practices, the grounding and bonding network components create a system that effectively safeguards personnel, property, and equipment The most common hazard in grounding and bonding networks is electric shock, which occurs from accidental contact with energized devices The effects of electrical shock are determined by the magnitude of current and duration of the shock

A Closer Look at Grounding and Bonding Grounding and bonding network components: Every building has a grounding electrode, a conductor that provides a direct, low-resistance connection to the earth A grounding conductor connects the electrical equipment to the grounding electrode and the building's main grounding busbar The main grounding busbar is a conductor that serves as a common connection point for two or more circuits; the busbar is solid copper with insulated standoffs

A Closer Look at Grounding and Bonding Grounding and bonding network components: Conductors used specifically for bonding are called bonding conductors; the conductor that connects the building’s service equipment ground to the telecommunications grounding system is called the bonding conductor for telecommunications (BCT) The BCT is a No. 6 AWG (American Wire Gauge) or larger insulated copper conductor that connects the equipment ground to the telecommunications main grounding busbar

A Closer Look at Grounding and Bonding Grounding and bonding network components: The telecommunications main grounding busbar (TMGB) is the foundation of the grounding system and it serves as an interface to the building’s power The TMGB also serves as a central connection point for the telecommunications bonding backbone (TBB) and equipment Usually there is one TMGB per building; it is typically in the entrance room (facility), the building entrance for both public and private network service cables, or in the main telecommunications room

A Closer Look at Grounding and Bonding Grounding and bonding network components: In each telecommunications room the telecommunications grounding busbar (TGB) provides a common access point of connection for systems and equipment bonding to ground The TGB is built in a similar fashion to the TMGB and it should be installed as close as possible to the panel board in the telecommunications room If a backboard (a panel for mounting system hardware and equipment) is located in the same room as a TGB, it should be bonded to the TGB

A Closer Look at Grounding and Bonding Grounding and bonding network components: The TMGB and all TGBs are interconnected by a No. 6 AWG or larger insulated conductor, the TBB The TBB’s primary function is to reduce or equalize differences in the telecommunications systems bonded to it; it is considered part of the grounding and bonding infrastructure, but it is independent of all equipment and cable The TBB begins at the TMGB and extends throughout the building, using the telecommunications backbone pathways

A Closer Look at Grounding and Bonding When planning TBB installation, the following design considerations are important: Be consistent with the design of the telecommunications backbone cabling system Use multiple TBBs if the building size permits it, but they must be bonded together at the top floor Bonding conductors between a TBB and TGB must be continuous and routed as directly as possible Don’t use interior water pipe systems or metallic cable shields as a TBB

Grounding and Bonding System vs. Equipment A building has six types of grounding and bonding systems designed to provide overall protection for the building and its occupants: Lightning protection system Grounding electrode system Electrical bonding and grounding system Electrical power protection system Telecommunications bonding and grounding system Telecommunications circuit protector system

Grounding and Bonding System vs. Equipment Grounding systems: Lightning protection systems provide a designed path for lightning current to travel Lightning protection systems are made up of several components: air terminals (lightning rods); conductors; ground terminations (ground rods); surge arresters; and surge protectors The telecommunications ground must be bonded to the lightning protection system within 3.7 meters of the base of the building

Grounding and Bonding System vs. Equipment Grounding systems (cont.): Grounding electrode systems are the end product of bonding together all metal underground water pipes, the metal frame of the building, any electrode that is encased in concrete, any ground ring, and any made or other electrodes Other electrodes include rod and pipe electrodes, plate electrodes, and metal underground systems Grounding electrode system forms a single, reliable ground for a building

Grounding and Bonding System vs. Equipment Grounding systems (cont.): Both the electrical bonding and grounding systems and the electrical power protection system refer to the requirements for all electrical installations, such as types, sizes, methods and locations of conductors and connections Three scientific principles guide bonding conductors: equalization, diversion, and coupling The type of bonding conductors used in most commercial buildings depends on the application and the fault-current-carrying capacity needed

Grounding and Bonding System vs. Equipment Equipment grounding: Each type of grounding equipment has its own set of grounding and bonding specifications The primary purpose of equipment grounding is to remove potentially dangerous voltages; it also protects against electrical shock and prevents heat building up in the equipment Earth grounding is an intentional connection from a circuit conductor to a ground electrode placed in the earth and it provides a safe path for the dissipation of fault currents

Grounding and Bonding System vs. Equipment Equipment grounding (cont.): The grounding conductor should be bonded to the nearest accessible earth-ground The bonding jumper must be no smaller than AWG 6 copper, it must be connected between the communications system grounding electrode and the building’s power grounding electrode system Termination is the connection of a cable to connecting hardware; the earth ground must terminate to the grounding electrode using either exothermic welding, listed lugs or clamps, or listed pressure connector

Grounding and Bonding System vs. Equipment Equipment grounding (cont.): An intrinsically safe system operates by preventing ignition of flammable or combustible material under normal or abnormal conditions The primary advantage of intrinsically safe systems is that ordinary wiring is allowed Intrinsically safe systems are composed of safe interconnecting cables, cable shields, enclosures, cable trays, and raceways; all items must be grounded with an equipment grounding electrode, and bonded with an approved method

Cable Protection and Equipment-Grounding Practices Inside cable and wire is that which runs from communications equipment to the protector All types of inside communication cables and wires must be rated for resistance to the spread of fire, be suitable for the installation site, and have a voltage rating of at least 300 volts; the conductors in these cables, other than fiber, must be copper Specific installation requirements include: the separation of communications cables and electrical power cabling; using approved firestopping methods; proper conduit use

Cable Protection and Equipment-Grounding Practices Inside cable and wire (cont.) When using an unshielded backbone cable, a TBB conductor should be used with it; the TBB must be bonded to the grounding using the grounding busbar nearest the termination point of the cable The shields of shielded cable are usually grounded at each end to a connector panel, which must be bonded to the closest approved ground In smaller equipment rooms, equipment is usually grounded via the closest ground; larger buildings with multiple equipment rooms require multiple TGBs

Telecommunications Circuit Protectors A telecommunications circuit protector is a device that protects telecommunications facilities and equipment from abnormally high voltages and current High voltage and currents are usually caused by exposure to lightning, accidental contact with electrical light, or power conductors operating at over 300 volts to ground There are three types of telecommunications circuit protectors: primary; secondary; and data and fire alarm

Telecommunications Circuit Protectors Primary protectors are most typically made from carbon blocks, glass tubes, or solid state When ready to install, follow these installation practices: they should be installed immediately adjacent to the exposed cable’s point of entrance; for long-term reliability, ensure that the installation is in a noncorrosive atmosphere; adequate lighting is very important; when installed in a metal box, bond the box with a grounding conductor directly to the protector’s ground; when installed outside, use cabinets, boxes and mounting hardware

Telecommunications Circuit Protectors Secondary protectors are typically made from heat coil, sneak-current fuse, or PTC resistors Secondary protectors must coordinate with the lightning transient and power-fault requirements of primary protection For this reason, secondary protectors often include primary protection device materials, and secondary protection is usually available as an option on primary protectors Secondary protectors must handle sneak current

How Documentation Helps You and Your Network The advantages of keeping documentation: It serves as a comprehensive reference It allows for easier additions, moves, and changes to equipment and workstations It can be a valuable source when troubleshooting It can provide the necessary justification for adding staff or equipment It provides proof that the installation meets a manufacturer’s hardware or software requirements It makes security management more effective

Chapter Summary All telecommunications systems require grounding and bonding systems. Several associations provide codes, standards, and minimum requirements for installing these systems. ANSI/EIA/TIA-607, “Commercial Building Grounding and Bonding Requirements for Telecommunications,” is the primary source of installation information. The second most important source is the NEC

Chapter Summary A grounding and bonding network is made up of insulated copper conductors. These conductors are run in parallel with the telecommunications cables, and link rooms containing telecommunications equipment to a common ground. The recommended size for these conductors range from No. 6 to No. 3 /0 AWG insulated copper

Chapter Summary These conductors are bonded to solid copper grounding busbars, which are installed in the entrance facility, the main telecommunications room, and all other telecommunications rooms. In addition to the conductors that run throughout the building, telecommunications equipment, frames, cabinets, raceways, and protectors are grounded to the busbars

Chapter Summary The busbars throughout the building are bonded together with a backbone cable of at least No. 6 AWG insulated copper. This backbone cable is also connected to the main grounding busbar, which is bonded to the electrical service (power) ground and an earth ground

Chapter Summary Telecommunications circuit protectors are used to protect telecommunications facilities and equipment from abnormally high voltages and currents. This protection is in addition to the requirements and recommendations for grounding and bonding telecommunications systems Documentation makes your job easier and helps you and your networks work more efficiently