Thursday, March 16, 2023
Hello CQD. Thank you for providing this service and I look forward to reading it every morning. My question is, where is the line drawn from when you need to get a UL evaluation for field installation of devices in an enclosure, as compared to installing one or two listed UL devices in an enclosure? Do you need UL evaluation of even the smallest of devices installed? Not sure of the process how this is determined. Is it up the AHJ? Thank you and awaiting your response. Keith Bailey
Keith, great question. The AHJ is the ultimately the one that approves an installation. Section 110.2 requires an installation to be approved, and Section 110.3 offers guidance on considerations for evaluating and judging if equipment is suitable or safe. Listing is one element to consider when evaluating equipment. For example, Article 409 provides guidance on the field wiring of Industrial Control Panels, an AHJ may approve an installation because the field wired Industrial Control Panel complies with Article 409, whereas an AHJ would like to require a listing of a factory assembled Industrial Control Panel for approval.
Field Evaluations are a listing mechanism for when equipment has already been installed or is already on site. Often a Contractor or AHJ may have some concerns about a piece of equipment, or maybe the authenticity of the listing is in question. A National Recognized Testing Lab (NRTL) can be hired to come out and perform a field evaluation and if the evaluation deems the equipment meets the appropriate standards, the NRTL will apply their Field Evaluation marking label. That marking provides assurance to the AHJ that the equipment is acceptable for the intended use, ultimately aiding in the AHJ’s approval. One important note about Field Evaluations, they are a one-off, and only apply to the specific installation site and piece of equipment that was evaluated. Here is a complete up-to-date list of NRTLs in OSHA’s NRTL program.