UL 508A Industrial Control Panel Build
The Difference: UL Listed vs. Recognized Components in UL 508A Industrial Control Panels
UL Listed components are complete, stand-alone products (e.g., power supplies) evaluated for safety in their intended use. Install them per manufacturer instructions.
UL Recognized components are "building blocks" (e.g., terminal blocks) evaluated for specific conditions within a larger UL Certified product. Use them strictly according to their "Conditions of Acceptability."
The key is that UL Listed items are ready-to-go, while UL Recognized items require careful integration based on their specific limitations.