National Electrical Code nuances... believe it, or not
OK, time for a short National Electrical Code/telecommunications quiz.
OK, time for a short National Electrical Code/telecommunications quiz.
- Where do you look for requirements for optical-fiber cabling? If you said Article 770, you're correct!
- Where do you look for requirements for CATV cabling? If you said Article 830, you're correct!
- Where do you look for requirements for telephone cabling? If you said Article 800, you're correct!
- Where do you look for requirements for data cabling? If you said Article 800, you're... wrong!
Article 725.41(A)(4) says:
Listed information technology (computer) equipment limited power circuits.
FPN: One way to determine applicable requirements for listing of information technology (computer) equipment is to refer to UL 1950-1995, Standard for Safety of Information Technology Equipment, Including Electrical Business Equipment. Typically, such circuits are used to interconnect information equipment for the purpose of exchanging information (data).
So, it's Article 725—believe it or not!
Article 800 currently covers traditional telephony and digital telephony circuits, while Article 725 covers those between information technology equipment (computers)—unless the voice and data are in the same cable, in which case Article 725.56(D)(1) refers back to Article 800.
Confused yet? Just wait, it gets better (or worse, depending on your perspective).
While it is not big news for most of us that Communications (codespeak for "voice") and Information Technology (codespeak for "data") have converged, this is not apparent from the recent reorganization of the NEC Code Panels by the Technical Correlating Committee, which placed Article 725 under the jurisdiction of Panel 3 and the communications articles (770, 800, 820, 830) under Panel 16. Logically, all the telecommunications articles should be under one panel.
BICSI will make a proposal to change the scope of Article 800.1 to read:
This article covers telephone, signaling/communications circuits and equipment not in an information technology equipment room, telegraph (except radio), outside wiring for fire alarm and burglar alarm, and similar central station systems; and telephone systems not connected to a central station system but using similar types of equipment, methods of installation, and maintenance.
FPN No. 1: For further information for fire alarm, guard tour, sprinkler waterflow, and sprinkler supervisory systems, see Article 760.
FPN No. 2: For installation requirements of optical-fiber cables, see Article 770.
FPN No. 3: For installation requirements for network-powered broadband communications circuits, see Article 830.
FPN No. 4: For installation requirements for equipment and circuits in an information technology equipment room, see Article 645.
Delete Section 725.41(A)(4) including the FPN.
Delete 'Exception: Limited power circuits used by listed information technology equipment' in Chapter 9 Section Tables 11(A) and 11 (B)."
Telecommunications structured cabling systems designers do not specify unique cabling for use with telephony or information technology. The cabling specified in Article 800 is to support voice, data, and countless other telecommunications applications.
This proposal would simplify the Code by bringing all data communications under Article 800. Don't you agree?
Next month, I plan to cover subtle changes in Code language that may have a huge effect on telecommunications cabling designs and specifications in the future.
Q: NEC Article 645 is causing us problems. In some instances, we have even had this article applied to computer labs in elementary schools.
Bitting Electric Inc.
A: I do not believe that a change in the NEC would correct your problem. The applicability of Article 645 is plainly stated in Article 645.2 Special Requirements for Information Technology Equipment Room, which says the following:
This article shall apply, provided all the following conditions are met:
- Disconnecting means complying with 645.10 are provided.
- A separate heating/ventilating/air-conditioning (HVAC) system is provided that is dedicated for information technology equipment use and is separated from other areas of occupancy. Any HVAC system that serves other occupancies shall be permitted to also serve the information technology equipment room if fire/smoke dampers are provided at the point of penetration of the room boundary. Such dampers shall operate on activation of smoke detectors and also by operation of the disconnecting means required by 645.10.
- Listed information technology equipment is installed.
- The room is occupied only by those personnel needed for the maintenance and functional operation of the installed information technology equipment.
- The room is separated from other occupancies by fire-resistant walls, floors, and ceilings with protected openings.
So, if the room does not meet each of these five requirements, it fails the applicability test. It would be highly unlikely that an elementary school computer lab would meet 645.2(4), which bars use of the computer equipment in the room by those for whom the computer room was constructed—the students. A point to tactfully address with your AHJ on your next project.
Q: I have a concern about the NEC requirement for optical-fiber innerduct to be installed per non-metallic tubing requirements. What purpose is served by installing pull boxes to eliminate bending in excess of 360°?
Recently, a "local governing authority" made us remove the listed plenum innerduct (and, of course, the fiber that was in it) because there were no pull boxes. He also said that the innerduct was "not suited for a plenum environment and unsafe for the childen in the school."
This requirement is counter-productive for optical-fiber installations, and I would like to see it taken out of the Code.
Victor D. Lanahan
A: First, an explanation of a few terms. In the NEC 2002, "innerduct" is used to describe the unlisted non-metallic flexible raceway used in underground or outside-plant construction. It is important to remember that innerduct must be terminated at the point of entrance. "Non-metallic optical-fiber raceway" is the listed non-metallic flexible corrugated raceway used inside the building. Code-making panels are very fussy about correct terminology.
Now for the details. Article 770.6, Raceways for Optical-Fiber Cables, says:
The raceway shall be of a type permitted in Chapter 3 and installed in accordance with Chapter 3. Exception: Listed non-metallic optical-fiber raceway identified as general-purpose, riser, or plenum optical-fiber raceway in accordance with 770.51 and installed in accordance with 362.24 through 362.56, where the requirements applicable to electrical non-metallic tubing shall apply.
Article 362.26, Bends Number in One Run, says:
There shall not be more than the equivalent of four quarter bends (360° total) between pull points, for example, conduit bodies and boxes.
This is the crux of your problem. I agree that it is illogical to require that pull points be installed in a raceway specifically designed to facilitate cable placement for extended distances without pull points. But this will certainly require a change in the NEC. This requirement is placing undue hardship on the technician installing the raceway and cable, and undue expense to the owner, while not affording any additional safety from electrocution where both the raceway and the listed cable are non-conductive.
The easiest solution would be to change Article 770.6 Exception to read,
Listed non-metallic optical-fiber raceway identified as general-purpose, riser, or plenum optical-fiber raceway in accordance with 770.51 and installed in accordance with 362.24 and 362.28 through 362.56, where the requirements applicable to electrical non-metallic tubing shall apply.
Subtle, isn't it? But this would eliminate the 360º restriction between pull points, while maintaining all other requirements.
I strongly suggest that you also submit a proposal to the NFPA before the November 1, deadline. See www.nfpa.org/ Codes/ProposalsAndComments.asp for an explanation of the process.
As for the suitability of non-metallic optical-fiber raceway for use in plenum spaces, the optical-fiber raceways covered in Article 770.51(E), (F), and (G) are raceways listed for use in plenum, riser, or general-purpose applications. Another point to tactfully address with the AHJ on your next project.
I am still having trouble visualizing how having a greater-than-360º bend in a non-metallic optical-fiber raceway could possibly endanger the safety of school-aged children.
Donna Ballast is BICSI's standards representative, and a BICSI registered communications distribution designer (RCDD). Send your questions to Donna via e-mail: firstname.lastname@example.org.