UL 508A Resources (Landing Page)

[APDahlen]

Explore DigiKey’s TechForum UL 508A control panel content.

This collection of engineering briefs is designed to help you select and integrate DigiKey products into your UL-certified industrial control panels and machines. This includes stand-alone wall-mounted panels as well as machine-mounted panels.

The Phoenix Contact TMC 81A 01A is a representative UL-listed product. This is a UL 489 listed circuit breaker suitable for branch circuit protection in a UL 508A control panel.

Figure 1: Image of a UL 489 listed circuit breaker suitable for branch protection in a UL-508A certified control panel.

What is UL 508A?

UL 508A is an American standard describing how to safely construct industrial control panels. It is harmonized with Canadian standards.

Where can I learn more about UL 508A?

The UL 508A standard is located here.

You are encouraged to participate in UL’s Industrial Control Panel Shop Program (ICP Program). On an individual level, there is value in obtaining UL’s Manufacturer Technical Representative (MTR) certification. This will give you the knowledge to understand how panels are constructed in accordance with the UL 508A standard so that they may then be UL-listed.

Core UL 508A topics

• What is Short Circuit Current Rating (SCCR)?

• Peak Let-Through Current FAQs for UL 508A Industrial Control Panel Fuses

• Understanding SCCR: Aligning Control Panel with Feeder Fault Current

Representative components for UL 508A control panel construction

• Circuit Breaker Branch Protection vs Supplementary Protector in a UL 508A Listed Control Panel

  • Circuit Breaker Auxiliary Contacts for PLC Monitoring

• Introduction to the Magnetic Motor Starter

  • Introduction to the 3-Wire Start-Stop Circuit
  • Use of an Interposing Relay for Increased Contactor Speed
  • Permanent Magnets as an Energy Saving Feature of a 3-phase Motor Starter
  • How Does a Motor Starter’s Thermal Overload Block Work?
  • What is Single-Phasing in a 3-phase system?

• What is a motor starter’s solid-state overload relay?

• Locating Siemens SMF Starters and MMS Switches for Fractional HP Motor Control

UL 508A Control Panel Construction

• Navigating UL 508A for Industrial Control Panel Enclosures

• How to Select a Wire Ferrule?

• Integrating a 120 VAC Programming Receptacle into a UL 508A Listed Control Panel

Related information

Please follow these links to related and useful information:

• DigiKey’s product selection guides

About this author

Aaron Dahlen, LCDR USCG (Ret.), serves as an application engineer at DigiKey. He has a unique electronics and automation foundation built over a 27-year military career as a technician and engineer which was further enhanced by 12 years of teaching (interwoven). With an MSEE degree from Minnesota State University, Mankato, Dahlen has taught in an ABET-accredited EE program, served as the program coordinator for an EET program, and taught component-level repair to military electronics technicians. Dahlen has returned to his Northern Minnesota home and thoroughly enjoys researching and writing articles such as this.