14.4 Communications Systems: Chapter 8 & Intersystem Bonding

14.4 Communications Systems: Chapter 8 & Intersystem Bonding

Prov's Kentucky journeyman outline lists Communication Systems as a separate content area (3 of 80 questions), and the ICC outline touches it through Special Equipment and grounding questions. Chapter 8 of the NEC covers telephone and data circuits, radio and television antennas, community antenna television (CATV), and broadband systems. These systems often share a building's grounding electrode system with the power wiring, so electricians install the bonding that ties them together.

---

1. How Chapter 8 Fits the NEC

Under NEC 90.3, Chapter 8 covers communications systems and is not subject to the requirements of Chapters 1 through 7 except where Chapter 8 specifically references them. When a question asks about a communications installation, look in Chapter 8 first, then follow only the references it makes, such as 250.94 or 300.22.

The 2023 NEC organizes Chapter 8 this way:

The 2017 and 2020 editions placed more of these rules in Article 800. If you test with an older NEC through Prov, the same topics are there under different section numbers. For example, Prov's sample question on listing communications equipment cites 800.18 from that numbering. Optical fiber cables and raceways are in Article 770 (Chapter 7).

---

2. Protection at the Building Entrance

Primary protectors (805.90)

A listed primary protector is required on each communications circuit that is run partly or entirely in aerial wire or cable not confined within a block, and on each circuit that could be exposed to accidental contact with electric light or power conductors operating at more than 300 volts to ground. The protector is located in, on, or immediately next to the building served, as close as practicable to the point where the conductors enter. The serving utility usually installs it, but the electrician often provides the bonding point.

Metallic sheaths and coaxial shields

The metallic sheath of a communications cable must be bonded or interrupted as close as practicable to its point of entrance (805.93). The outer conductive shield of a CATV coaxial cable must be bonded as close as practicable to its point of entrance (820.93).

Bonding conductor and the 20-foot rule (800.100)

If a 20-foot bonding conductor cannot reach the building's grounding means at a one- or two-family dwelling, the exception permits a separate communications ground rod at least 5 feet long, bonded to the power grounding electrode system with a conductor not smaller than 6 AWG copper. Separate electrodes must always be bonded together. Otherwise, a lightning strike or power fault can create a large voltage difference between the systems, and that difference appears across the equipment that connects them, such as a television or modem.

---

3. The Intersystem Bonding Termination (250.94)

An intersystem bonding termination (IBT) is a device that gives communications, CATV, and antenna installers a clean place to bond to the power grounding system. At the service equipment (and at the disconnecting means for any additional building or structure), the IBT must:

1. Be accessible for connection and inspection.
2. Have terminals for not fewer than three intersystem bonding conductors.
3. Not interfere with opening the service, building disconnecting means, or metering equipment enclosure.
4. Be securely mounted and connected to the service equipment enclosure, the meter enclosure, or an exposed nonflexible metallic service raceway, or be mounted at one of these enclosures and connected to it or to the grounding electrode conductor with at least 6 AWG copper.
5. Be listed as grounding and bonding equipment.

An exception to 250.94 waives the IBT in existing buildings where the communications bonding conductors are already installed, provided an accessible means for connecting them exists.

---

4. Radio and Television Antennas (Article 810)

• Avoid contact with power (810.13): Outdoor antennas and lead-in conductors may not cross over open conductors of electric light or power circuits, and they must be kept well away from them to avoid accidental contact.
• Masts and metal structures (810.15): Antenna masts and metal structures that support antennas must be grounded through a bonding conductor.
• Antenna discharge units (810.20): Each lead-in conductor from an outdoor antenna must have a listed antenna discharge unit (lightning arrester). It may be located outside the building or inside between the point of entrance and the radio or TV set, as near as practicable to the entrance of the conductors.
• Bonding conductor (810.21): The conductor from the mast and the discharge unit must be not smaller than 10 AWG copper, 8 AWG aluminum, or 17 AWG copper-clad steel or bronze. It is run in as straight a line as practicable and connects to the intersystem bonding termination or another point on the building's grounding electrode system.

---

5. Cables, Raceways, and Separation

Cable types and substitutions

Communications cables are listed by their fire performance. A cable with a higher rating can always replace a cable with a lower rating:

Communications raceways are listed as plenum, riser, or general-purpose types and are used like the matching cables.

Separation from power conductors (805.133)

• Communications wires and cables must not be placed in any raceway, compartment, outlet box, junction box, or similar fitting with conductors of electric light, power, Class 1, non-power-limited fire alarm, or medium-power broadband circuits, unless a permanent barrier or a listed divider separates them, or the power conductors are in the enclosure only to supply the communications equipment and are routed to keep at least 1/4 inch (6 mm) of separation.
• In other applications, communications conductors must be separated by at least 2 inches (50 mm) from light and power conductors, unless the power conductors are in a raceway or in metal-sheathed, metal-clad, nonmetallic-sheathed, Type AC, or Type UF cable, the communications conductors are in a raceway, or a continuous, firmly fixed nonconductor separates them.

Outside the building (800.44, 800.47, and 800.53)

• Communications cables on poles run below power conductors, and above roofs they must have at least 8 feet of vertical clearance, with exceptions for certain roofs and short spans.
• Underground communications cables in a raceway, handhole, or manhole with power conductors must be separated from them by brick, concrete, or tile partitions or another suitable barrier.
• Where practicable, communications wires and cables on buildings are kept at least 6 feet from lightning protection conductors.

Inside the building

Cables must be supported by the building structure, not by ceiling grid or ceiling support wires, and the accessible portion of abandoned communications cable must be removed unless it is tagged for future use (800.25). Penetrations of fire-resistance-rated walls, floors, and ceilings must be firestopped (800.26).

---

6. Kentucky Licensing Note

KRS 227A.030(8) says Kentucky's electrical licensing law does not apply to a person performing work for a telecommunications company where the voltage is 50 volts or less. A journeyman working for an electrical contractor still installs the intersystem bonding termination, the bonding conductors to the power grounding system, and any power circuits that supply communications equipment.