Do raceway wire fill restrictions apply to limited energy cable pulls?
As part of a remodeling project at a school, an electrical contractor needed to run data lines to each seat in the classroom. The principal wanted every student to be able to be on-line at the same time:allowing the teacher to float from student to student, checking their internet research. This resulted in a large number of cables feeding into a network connection point within an adjacent communications wiring closet. This closet contained a network node point, connecting the signals to a central server, which, in turn, maintained the connection to the exterior telephone lines and the internet. Although the contractor successfully pulled these lines into an existing raceway, the cable fill easily exceeded the normal threshold of 40%. The inspector rejected the job, saying the 40% limitation applied.
The EC&M Panel's response. We think the 40% limitation doesn't apply to these cables, but we recognize the Code may be moving in the opposite direction. The cabling comes under Art. 725 because it involves signaling without a direct connection to the telephone system.
The circuits between the classroom computers and the central server undoubtedly qualify under the provisions of Sec. 725-41(a)(4) as limited energy circuits. Sec. 725-52 requires such circuits meet the insulation and application requirements of Sec. 725-61 and Sec. 725-71 (we assume the appropriate cabling was used, since the inspector never challenged that). In addition, Sec. 725-52 requires separation between the limited energy cabling and power wiring, but that isn't in question either.
Sec. 90-3 nominally requires the application of all relevant Chapter 1-4 provisions to Chapter 5-7 applications, unless those articles supplement or modify the general rules. Sec. 725-3 does just that by saying only the provisions of Art. 300 (mentioned specifically within Art. 725) apply.
In the ca se of Class 1 circuits, Sec. 725-28(b) does reference Sec. 300-17. In so doing, it implicitly embraces the wire fill restrictions within the various Chapter 3 raceway articles. We think it highly significant that for Class 2 circuits no such reference exists. We think it would be contrary to the overall intent of the requirements to impose a wire fill limitation at this point, nor can we think of any safety issue. Remember, Sec. 725-8 applies Class 1 wiring restrictions (including wire fill) on these circuits only if their failure constitutes a life or fire hazard. We doubt a failure to complete an internet connection rises to this degree of importance. Finally, we aren't aware of any serious or widespread attempts to apply wire fill restrictions to these circuits over the past half century.
If the phone lines come to each desktop... All that said, we do want to point out a major change in Art. 800. Sec. 800-48 includes wire fill and similar restrictions on communications circuits, for the first time since the 1940 NEC. It does this by way of mandating compliance with all Chapter 3 rules on the enclosing raceways, not just Art. 300. If an outside telephone system extends to each desktop, then you need to observe these limits. There wasn't any substantiation of a safety issue to motivate this change. The proposal's (from the nonmetallic raceway industry) principal objective was to set up the exception that follows, recognizing nonmetallic communications raceways that aren't Chapter 3 wiring methods. In addition, none of the other Chapter 8 articles contain correlating language.
We think the panel should revisit this issue and either return this to historical practice, or else substantiate a safety issue behind the restriction. If the panel does the latter, it should also entertain similar changes throughout Chapter 8 for the sake of technical consistency.
