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Illustrated Catastrophes

Sep 1, 2009 12:00 PM, By Brian J. McPartland, NEC Consultant

More Code catastrophes uncovered and corrected in these faulty installations

These two installation photos were contributed by Pierre Belarge, president of Electrical Training Solutions in Elmsford, N.Y. Belarge, who is an International Association of Electrical Inspectors (IAEI)-certified inspector, encountered these examples of what not to do while conducting a routine inspection.

In both cases, the installations violate the wording of 300.15, which clearly states that “at each conductor splice point, outlet point, switch point, junction point, termination point, or pull point” a box or conduit body must be used where the wiring method employed is “conduit, tubing, Type AC cable, Type MC cable, Type MI cable, nonmetallic sheathed cable, or other cables,” unless one of the subsections [300.15(A) through (M)] to the basic rule permits such application. The installations shown in these two photos are not covered by any of those subsections, which are essentially exceptions to the basic requirement for some sort of Code-recognized enclosure at each “switch point” and “splice point.”

The attic switch (see Photo above) is also in violation of the general secure-support requirements given in 300.11. The use of a single nail to attach the switch to a building structure should not be considered as meeting the criterion of “…securely fastened in place” simply because the switch can still move, which will put stress on the connection point. Note the use of masking tape on the device terminals. Yikes! It makes you wonder what was on the mind of the installer.

Additionally, the flying splice (see Photo below) shows a violation of the specific support requirements for Type NM cable given in 334.30. As stated in 334.30, “Nonmetallic sheathed cable shall be supported and secured…at intervals not exceeding 1.4 m (4½ ft) and within 300 mm (12 in.) of every outlet box, junction box, cabinet, or fitting.” It appears the installation is a bit light on staples.

Although you can't see it in the flying splice photo, thanks to the beautiful tape job, the two cables are of dissimilar metals. One is copper; the other is aluminum. This clearly fails to comply with the requirement of 110.14, which states, “Conductors of dissimilar metals shall not be intermixed in a terminal or splicing connector where physical contact occurs between dissimilar conductors.” That wording is followed by examples of dissimilar metals, which specifically identify “copper and aluminum” as one example.

The co-mingling of copper and aluminum is especially dangerous, as was revealed in the past when aluminum conductors were attached to wiring devices (e.g., toggle switches and receptacles) that were equipped with copper terminating screws. The expansion and contraction rate of these two metals is quite different. What happened during thermal cycling was a phenomenon known as “creep and cold flow,” which resulted in a high-impedance connection. These high-impedance terminations became excessively hot during normal use and resulted in a number of fires.

Although the NEC is to be applied and enforced as written, sometimes compliance with the “letter of the law” is next to impossible. Where a job does not appear to meet the literal wording of a Code rule, one should determine whether or not the installation has satisfied the “spirit of the law.” If there was no practical way to fully meet the literal wording of the NEC — but the safety issue at the heart of the rule has been satisfied — then such an installation generally should be accepted.

In the coming editions of “Illustrated Catastrophes,” a focus will be placed not only on the Code's literal wording, but also on the hazard the rule is meant to address. By developing a clear understanding for the “letter” and “spirit” of the law, one will be better able to evaluate specific installations, especially those that do not seem to be directly addressed in the Code or so-called “gray areas.” This form of analysis will provide a sound basis for safe and effective design and installation.

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