This is more of an "insurance" issue than a mandate...Also UL is not the only firm permitted to "approve" equipment for use as marketed by the vendor. There are a few agencies, UL simply is the most common. Most Nationally Recognized Testing Laboratories (NRTL) are registered and approved with exception to crossing European standards or Canadian. The client and their insurance holders will determine the needs to list something as approved. In most cases (99%) it will be required.
Hope this helps - Also inquire to local codes as the AHJ could very well require this certification as an additional means of assurance to a quality standard.
Agree with Tom, and I will add:
Hope this helps.
Mr. Greene thank you for your most interesting inquiry.
As described within the 2017 NEC Handbook Article 100 on page 20, commentary on the term "Labeled" includes:
"Equipment and conductors required or permitted by the NEC are acceptable only if they have been approved for a specific environment or application by the AHJ as stated in Section 110.2. "Approval." Listing or labeling by a qualified testing laboratory provides the basis for approval."
Further commentary in Article 100 involving usage of the term "Approved" is worth reading as well. The commentary involves NFPA_79 "Electrical Standard for Industrial Machinery" which can be used in the process of determining suitability by the AHJ using Field Evaluation by a qualified laboratory or individual.
When such an evaluation is conducted on site, NFPA_790 "Standard for Competency of Third-Party Field Evaluation Bodies" can be used to qualify evaluation services. NFPA_791 "Recommended Practice and Procedures for Unlabeled Equipment Evaluation" can be used to evaluate unlabeled equipment in accordance with nationally recognized standards and any requirements of the AHJ.
Purchasing a copy of the NEC Handbook might be valuable as it contains many examples and illustrations of code questions. You can purchase a copy at: www.nfpa.org/70purchase
Hope this helps,
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