Bonding point for phone, cable TV and internet lines
Each service, and the disconnect of each building fed by a feeder or branch circuit, needs an intersystem bonding termination (or the alternative busbar): a listed, accessible connection point with room for at least 3 bonding conductors from phone, cable TV, antenna and fiber systems.
What the code requires
The intersystem bonding termination, usually called the IBT, is where communications systems bond to the building's electrical grounding. It is required outside the enclosures at the service equipment or meter enclosure, and at the disconnect of any building supplied by a feeder or branch circuit.
The IBT must be accessible, have terminals for at least 3 intersystem bonding conductors, not get in the way of opening any enclosure, and be listed as grounding and bonding equipment.
At the service, it mounts on the metal service or meter enclosure or on an exposed nonflexible metal service raceway, or connects to the grounding electrode conductor's metal enclosure with at least 6 AWG copper. At other buildings, it mounts on the disconnect's metal enclosure or connects to the grounding electrode conductor enclosure with at least 6 AWG copper.
As an alternative, a busbar at least ¼ in. by 2 in., with room for at least 3 communications terminations and listed connectors, may be used. It is tied to the grounding electrode system by a conductor at least as large as the biggest grounding electrode conductor on the bar or the size required under 250.94(A), whichever is larger.
On the job
- A new service with no IBT is a common correction.
- Cable TV or phone wiring with no bond back to the building's electrical grounding at the IBT gets flagged.
- The IBT is for communications, cable TV, radio and TV antenna, and optical fiber systems (Articles 770, 800, 810 and 820). It is not the bonding point for solar PV systems.
Exceptions that matter
- Existing buildings that already have the bonding or grounding conductors required by 770.100(B)(2), 800.100(B)(2), 810.21(F)(2) or 820.100 need no IBT. An accessible external connection point is permitted instead, such as an exposed nonflexible metal raceway, an exposed grounding electrode conductor, or another approved means.
- No IBT is required where communications systems are not likely to be used.
What changed in 2023
The 2023 edition reorganized the mounting rules and added a rule for sizing the conductor that ties the alternative busbar to the grounding electrode system.
Related sections
- NEC 770.100
- NEC 800.100
- NEC 810.21
- NEC 820.100
- NEC 250.64
- NEC 250.92
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CSLB #354550 · C-10 Electrical · Licensed since 1978 · $25,000 contractor's bond