Verify a sign fabrication shop's UL 48 listing status and confirm what a sign's UL label actually covers before accepting, installing, or permitting an electric sign

Steps

1. Ask the shop for its NRTL file/listing number and confirm the listing is under UL 48 (Standard for Electric Signs) at the sign-assembly level, not just a component-level listing such as the transformer alone
2. Look up that file number in the certifier's own online directory (e.g., UL's certifications lookup) to confirm the listing is active and the listee name matches the name printed on the sign's label
3. Read the physical label itself: it must show the certifier's mark plus manufacturer/listee identification and electrical ratings consistent with NEC 600.4 marking rules; note that current UL practice allows a single 'Electric Sign' mark on the raceway/enclosure housing the power supply instead of a separate mark on every section, so absence of a label on a given section is not automatically a defect
4. Confirm the listing's scope actually matches what was built (sign type, illumination method, number of sections, any field-added retrofit kit) — a UL 48 label does not itself certify code compliance; the local electrical inspector still separately enforces NEC Article 600 and any local sign ordinance
5. If any section was field-labeled rather than shop-certified, identify which NRTL or field-evaluation body issued that label, since not every AHJ accepts every field-labeling service