The rules in 250.94 are all about proper termination of communications system bonding terminals. If done correctly, properly terminating the bonding terminals in a communications system results in preventing a situation where a difference in voltage potential exists between the premises electrical system and the communications system. The most common method to bond communications systems is with an intersystem bonding terminal (IBT) in accordance with 250.94(A).

The IBT is required to be installed external to the service equipment, or for buildings supplied by other than a service, adjacent to the disconnecting means for the building or structure. Having the IBT external to the service or disconnect ensures that those installing communications systems can access the terminal without the need to open an electrical panel that may not be covered within the scope of their license.

Section 250.94(B) also recognizes an additional bonding method besides the IBT. This section allows connections to an aluminum or copper busbar not less than 1∕4 in. thick × 2 in. wide and of sufficient length to accommodate at least three terminations for communication systems in addition to other connections. This is commonly used in multi-occupancy commercial buildings for grounding electrode conductors in accordance with 250.64(D) & (F).

Using the method in 250.94(B) permits communications system bonding conductors as well as other bonding conductors to land on this common busbar. This provides relief for those installing new gas piping, vacuum or compressed air lines that require bonding. Often a new gas water heater or other appliance is installed on an existing building and proper gas pipe bonding is never done since the scope of the license for the gas piping installer may not allow opening the electric panel to make grounding or bonding terminations.

Below is a preview of the NEC^®. See the actual NEC^® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2020 NEC^® edition of NFPA 70.

2020 Code Language:

250.94 Bonding for Communication Systems. Communications system bonding terminations shall be connected in accordance with 250.94(A) or (B).

(A) The Intersystem Bonding Termination Device. An intersystem bonding termination (IBT) for connecting intersystem bonding conductors shall be provided external to enclosures at the service equipment or metering equipment enclosure and at the disconnecting means for any additional buildings or structures. If an IBT is used, it shall comply with the following:

Refer to the NEC^® text for six bonding requirements mentioned in 250.94(A). (These only apply to the intersystem bonding terminal, NOT the “other means” which is in 250.94(B))

(B) Other Means. Connections to an aluminum or copper busbar not less than 6 mm thick × 50 mm wide (1∕4 in. thick × 2 in. wide) and of sufficient length to accommodate at least three terminations for communication systems in addition to other connections. The busbar shall be securely fastened and shall be installed in an accessible location. Connections shall be made by a listed connector. If aluminum busbars are used, the installation shall also comply with 250.64(A).

Exception to (A) and (B): Means for connecting intersystem bonding conductors are not required where communications systems are not likely to be used.

Informational Note: The use of an IBT can reduce electrical noise on communication systems.