The 3rd edition of UL 508A was published in 2018, and it introduces several significant changes and improvements to the standard. Some of the key changes include:

If you need UL 508A for active panel design or UL listing, purchase the 4th Edition . If you specifically require the 3rd Edition for legacy equipment, contact UL Standards directly at 1-888-853-3503 or visit https://www.shopulstandards.com and request a historical PDF – specifying you want the “final revision of the 3rd Edition before the 4th Edition was issued.”

Using a pre-3rd edition PDF is not just inefficient—it is non-compliant with current NEC and OSHA expectations.