Last edit: 12/06/2026
The Chicago Connection
The origins of UL 508A can be traced directly to the City of Chicago during the early 1970s. At that time, industrial control panels were widely used in factories, commercial buildings, and industrial processes, but there was no comprehensive certification program specifically intended for custom-built control panels.
Many industrial control panels were essentially “one-off” assemblies built for a specific machine or process. Individual components inside the panels—such as motor starters, relays, disconnect switches, pushbuttons, timers, and transformers—might have been UL Listed or UL Recognized, but the panel as a complete assembly typically had no overall certification.
This situation created difficulties for electrical inspectors. Local code officials needed a consistent method for evaluating whether industrial control panels were electrically safe, especially when the equipment was custom-built and lacked a formal listing.
The individual most often associated with initiating the effort to create an industrial control panel evaluation program was William Hogan, the Chief Electrical Inspector for the City of Chicago. Hogan recognized that inspectors needed a practical and technically sound method for evaluating industrial control panels that did not have complete certification as finished assemblies.
The City of Chicago approached Underwriters Laboratories in the early 1970s and requested the development of a program that could be used to evaluate industrial control panels for electrical safety. This request became the foundation for what would eventually evolve into UL 508A.
The request was particularly important because Chicago had long maintained one of the most rigorous electrical inspection environments in the United States. A program accepted in Chicago would likely gain credibility in other jurisdictions as well.
