The 2008 National Electrical Code (NEC) includes a new definition covering “Intersystem Bonding Termination” and a total rewrite of Section 250.94 covering the requirements for installing a bonding connection point for communications systems. Only time will tell if the communications industry will use or disregard the intersystem bonding termination, as so often was the case with the old method of using a No. 6 bare copper conductor stubbed out of the service panel.
This new definition and text was suggested and supported in proposals and comments by the telecommunications industry. Since this new system provides an increase in usability and effectiveness, use of the intersystem bonding termination would seem a foregone conclusion.
In the 2005 and previous NEC editions, an accessible means external to the electrical enclosures must be installed for connecting intersystem bonding and grounding-electrode conductors. The connection point was required to be available or installed at the electrical service equipment for the premises and at the disconnecting means for any additional buildings or structures. This connection point was permitted to be on exposed nonflexible metallic raceways, such as the overhead or underground service conduit; connected to an exposed grounding-electrode conductor, such as the No. 4 copper grounding-electrode conductor to the concrete-encased electrode; or must be an approved means for the external connection of a copper or other corrosion-resistant bonding or grounding conductor to the metal raceway or to the equipment enclosure.
Often, a nonmetallic conduit was installed for the overhead or underground service or separate building conduit, or an insulated grounding--electrode conductor, or a painted grounding--electrode conductor was used, requiring a No. 6 AWG bare copper conductor to be provided. This No. 6 copper conductor, with one end connected to the metal of the disconnect enclosure and 6 inches or more of the conductor made available for terminating the grounding-electrode or bonding conductor from the communications system, could be used by the communications contractor.
At times, this bare copper conductor, the metal service conduit, and the metal of the disconnecting-means enclosure were all painted prior to the communications contractor installing the grounding electrode conductor connection with the resulting termination made without removing the paint. The paint provided a dielectric separation between the communications system and the electrical system resulting in either a poor bond or none at all between the systems.
The change for the 2008 NEC should provide a more reliable connection between the electrical system and the various communications systems installed. The new definition explains that an intersystem bonding termination is a device that provides a connecting point for communication grounding and bonding systems to the electrical service equipment or to the disconnecting means for a feeder or branch circuit at a separate building or structure. Section 250.94 requires the intersystem bonding termination to be accessible for connection and inspection of the communication grounding and bonding system. The termination must have the capacity for connection of not less than three intersystem bonding conductors and must not interfere with the opening of the service or metering equipment enclosure.
There are three different types of intersystem bonding terminations permitted. The first method is a set of terminals mounted and electrically connected to the meter enclosure. The terminals must be listed as grounding and bonding equipment. The second method is a bonding bar near the service or meter equipment enclosure or close to the raceway for the service conductors. This bonding bar must be connected with a minimum 6 AWG copper conductor to equipment-grounding conductor or conductors in the service enclosure, meter enclosure or in an exposed nonflexible metal raceway. The third method is the installation of a bonding bar near the grounding-electrode conductor. The bonding bar must be connected to the grounding-electrode conductor by a minimum 6 AWG copper conductor. The electrical contractor is responsible for the installation of the intersystem bonding termination, and the communications contractor is responsible for the connection of the communications bonding conductors to the terminal bar.
There is an exception in 250.94 permitting existing buildings or structures with intersystem bonding and grounding conductors from optical fiber cables per 770.93, telephone systems per 800.100(B), radio and television equipment grounding per 810.21(F), CATV system grounding per 820.100(B), and broadband communication system grounding per 830.100(B) to not have an intersystem bonding termination.
Additional text in the exception recognizes the installation requirements for grounding and bonding from the 2005 and previous Codes, but this only applies to existing buildings or structures.
The question, however, still remains: Will the communications systems in the future be connected to the new “intersystem bonding termination” or will the new terminations also be disregarded by the telecommunications industry?
ODE is a staff engineering associate at Underwriters Laboratories Inc., in Research Triangle Park, N.C. He can be reached at 919.549.1726 or at firstname.lastname@example.org.