UL 508A Standard for Industrial Control Panels

UL 508A certification is an industrial control panel directive, which is sought by electrical inspectors. The UL 508A Listing Mark on an industrial control panel provides evidence of third party certification to the municipal inspection authority and to the purchaser of the panel. A UL 508A Listing Mark shows that the panel complies with an acceptable safety standard.

The official definition of an industrial control panel, according to UL, is "an assembly incorporating two or more pieces of industrial control equipment or related control circuit devices, provided with interconnecting wiring and terminals for connections in the field. To allow the installer to properly install the panel in accordance to National Electrical Code (NEC) and other codes, electrical ratings and instructions are to be clearly explained on the panel."

Installation of a control panel can be completed in two ways: in an enclosure as "enclosed type" equipment, or arranged onto a mounting panel as "open type" equipment. For "open type" equipment, the assembly is installed in an enclosure provided by others, or at the installation site. Any of the outdoor enclosures or cabinets manufactured by Purcell Systems that carry the UL 508A Listing Mark would be classified as “enclosed type”, and complies with the applicable requirements for outdoor panels noted in the UL 508A standard.

UL 508A Certified Enclosures

Benefits of selecting an enclosure or cabinet that carry the UL 508A certification include:

  • UL 508A certification provides the inspection authority and your customer evidence that the control panel complies with nationally recognized safety standards. These standards ensure public safety, and provide assurances that the electrical control panel is compliant with national and local electrical codes.
  • Manufacturers that carry the UL 508A certification are subject to periodic unannounced inspections of their facilities by UL personnel. Through periodic audits of the manufacturers, UL can insure the manufacturer continues to meet the UL requirements for 508A certification.
  • For a control panel to carry the UL 508A Listing Mark, the panel must contain only UL recognized and listed components. The UL Mark on a component means that UL has evaluated and tested samples of this component and has concluded that they meet the UL requirements. This protects the quality and integrity of the enclosure and provides guarantee of safe performance.

Outdoor Enclosures and Cabinets

Within the UL 508A standard, there are two sections that are more relevant to outdoor enclosures and cabinets. The GENERAL section addresses requirements for all enclosures, and these requirements include:

  • Protection Against Corrosion
  • Support and Securement of Live Parts
  • Spacings
  • Conduit Bushings
  • Insulating Barriers
  • Insulating Materials
  • Grounding - General
  • Grounding - Size of Terminal or Bonding Conductor
  • Identification of Grounding and Grounded Circuit Conductors and Terminals


The OUTDOOR PANEL section addresses requirements for outdoor enclosures, and these requirements include:

  • Enclosure Openings
  • Accessibility of Live Parts
  • Ventilation Openings
  • Bonding
  • Enclosure Environmental Control Devices
  • Field Wiring
  • Internal Wiring
  • Disconnect Switches
  • Branch Circuit Protection
  • Markings