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Cord Wiring From Overhead

Apr 1, 1998 12:00 PM, Frederic P. Hartwell

When dropping cord out of an overhead wireway or busway, the Code limits the amount of horizontal travel to a point of attachment. What if it isn't attached?

With today's flexible equipment layouts to accommodate changes in production styles, many designers call for cord connections to overhead raceways. That allows the enterprise to reposition this equipment quickly as needed. We got a question recently as to how the distance restriction (6 ft) in the NEC might limit repositioning equipment. Specifically, could a cord be draped horizontally any distance as long as it wasn't attached to the building surface beyond the stated Code limits? In this case, everyone did agree the facility was providing adequate strain relief at the supply end of the cord; the only issue was horizontal travel of the cord.

The EC&M Panel's response. We think the distance limit only applies to a building surface attachment, but nevertheless there are other rules that limit horizontal positioning. Sec. 400-8 Ex. covers the general case: Flexible cord and cable shall be permitted to have one connection to the building surface for a suitable tension take-up device. Length of cord or cable from the supply termination to the take-up device shall be limited to 6 ft (1.83 m).

This exception dates from the 1990 NEC, and the substantiation for the exception directly referenced the prohibition in Sec. 400-8(4) against using flexible cord "where attached to building surfaces." Therefore, we don't think either the literal text or the original intent go beyond the surface attachment point.

However, we also think going very far away from a direct vertical drop begins tosmell like using cord to substitute for the permanent wiring of a building, not to mention raising subjective problems of workmanship. Exactly how much, however, is a judgment call on the part of the AHJ. For example, 8 ft off vertical in a high-bay building originating 35 ft above the floor could look reasonable, but the same horizontal offset distance below a wireway 10 ft above the floor might be problematic.

The other issue concerns the weight of the cord. If it hangs straight down, standard tension devices work very well. As you run it horizontally and try to keep it taught to avoid floor traffic, you also increase the stress on the cord and its supports. Remember cords, particularly the larger ones, weigh a lot. When you add the strain of the catenary as you pull on it, you add even more stress to the segment of cord being squeezed by the strain-relief basket. We think this could be a legitimate concern of an inspection authority.

Note that if the cord originates at a busway, Sec. 364-8(b)(2) Ex. for industrial establishments allows longer cord lengths attached at multiple points to building surfaces, provided there is qualified maintenance and supervision. We think that is a better approach, although it only applies to busway drops.

The exception in Sec. 400-8 presently applies to other sources as well, such as wireways, which have been used for this purpose for generations. In these other cases, there isn't any way to avoid the 6-ft single-attachment restriction, although again, we think there needs to be some latitude for horizontal movement under this support, as long as it isn't tantamount to substituting flexible cord for permanent wiring. This is, and must remain, a judgment call on the part of the inspector.

These answers are given by our panel of experts. This author chairs the panel. Other panel members include: Bill Summers, James Stallcup, and Dan Leaf. The opinion expressed is that of the panel. If a panelist disagrees with the majority opinion, his explanation is printed following the answer. Although authoritative, the answers printed here are not, and cannot be relied on as formal interpretations of the NEC.

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