Approved-by whom?

Specify which standards body is doing the approving

DOCUMENTS DEALING WITH electrical system or apparatus safety often include a requirement that some material or device be "approved" for the specific application. That has resulted in some controversy, including repeated revisions of portions of the National Electrical Code.

For an explosion-proof motor, "approved" is usually taken to mean labeling by Underwriters Laboratories for a particular class and group of hazardous atmosphere. Is UL the only agency that could be allowed to apply such labeling? No; government regulations provide for certification of other "nationally recognized Testing Laboratories" (NRTL's) to establish product design and manufacturing criteria based on tests. As yet, however, UL is the only significant NRTL for electric motors.

Over the years, much argument has concerned the use of the words listed, approved, and identified to signify product acceptability. In the 1978 NEC, for example, lighting fixtures in hazardous atmospheres had to be "approved" for the purpose. By whom, or in what way, was not stated. The corresponding passages in today's NEC use the term "identified" instead, which in 1978 referred only to distinction between one conductor or terminal and another. A much broader meaning of "identified" is now made clear.

NEC section 600.3 requires electric signs to be "listed" rather than approved or identified, and Article 422 mentions certain "listed" appliances. Not surprisingly, the Code defines "listed" as "included in a list" published by an NRTL, inspection agency, or "other organization concerned with product evaluation." Again, most (but not all) such listings originate with UL.

Based on all that, "listed" and "identified" have clear meanings-at least in the context of the NEC-whereas "approved" is much less clear. When specifying apparatus or methods for any electrical installation, then, use the term "approved" only when you define who does the approving, how approval is to be expressed, and what backs it up. Otherwise, approval may mean nothing more than what a supplier considers appropriate.

By Richard L. Nailen, P.E., EA Engineering Editor

Copyright Barks Publications May 2005
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