Do you know the purpose of the UL 508A standard for industrial control panels and the key topics it covers? This post explains the intent of UL 508A and summarizes the major sections of the standard. Additional topics covered in this post include:
- What is UL 508A certification?
- What is UL 508A Listing?
- 2 types of UL 508A industrial control panel listing labels
- Addition to the UL 508A standard – Manufacturer’s Technical Representative (MTR) program
The UL 508A Standard
What is UL 508A?
UL 508A is the Underwriters Laboratories (UL) reference standard for the construction of industrial control panels in the United States. Industrial control panels are defined by the National Electric Code (NEC) section 409.2 as “an assembly of two or more power circuit components, control circuit components, or any combination of power and control circuit components.”
Based on the safety rules recommended by the NEC, control panel manufacturers follow UL 508A for guidance in various areas of design and assembly. The standard also includes specifications to ensure that industrial control panels can endure environmental factors such as dust, moisture, temperature fluctuations, and corrosion.
Key Areas of UL 508A
The UL 508A standard is organized into sections; each addresses specific aspects of industrial control panel construction, marking, and performance. Key sections include:
- Electrical Safety: Control panel design guidelines to prevent various hazards, such as electrical shock, short circuits, overheating, arc flash, and fire hazards.
- Component Selection: Specific requirements for properly selecting and using electrical components within industrial control panels to ensure their safety and reliability. Addresses compatibility, listing and certification, suitability for intended use, and documentation.
- Wiring Methods: Specifications for control panel wiring installation and routing to avoid electrical hazards, mechanical damage, interference, and crosstalk. Includes wire sizing and selection criteria, routing and bundling, termination, grounding and bonding, and identification and marking.
- Environmental Considerations: Guidelines for ensuring that industrial control panels can tolerate environmental factors and operate reliably in their intended application. Addresses areas such as enclosure type, gasketing and sealing, ventilation and cooling, temperature variations, and corrosion resistance.
- Marking and Labeling: Instructions for labeling control panels with appropriate information about the manufacturer, standards compliance, ratings, warnings, and instructions.
- Construction and Assembly: Specifications for control panel construction and assembly, including mounting of components, enclosure design, accessibility, and serviceability.
- Documentation: Criteria for required documentation related to the design, construction, and installation of industrial control panels. Drawings, schematics, component lists, and testing records may be included.
- Special Applications: Specific requirements and considerations for industrial control panels used in specialized or unusual applications that may pose unique challenges or hazards.
UL 508A Certification
What is UL 508A Certification?
UL 508A certification refers to the process industrial control panel manufacturers go through to obtain a UL Listing Mark on their panels. While the term UL 508A certification is used frequently, the official UL term is UL Listing.
UL 508A Listing
The UL 508A Listing Mark on an industrial control panel indicates that the panel has been independently evaluated and tested by a UL inspector and certified to comply with the standard. UL 508A Listing is important to the municipal inspection authority and the purchaser of the panel, indicating that the control panel meets recognized safety standards for electrical equipment used in industrial settings.
The UL 508A Listing covers panels operating from a voltage of 1000 volts or less.
Why Your Industrial Control Panel Should Be UL 508A Listed
There are many reasons to obtain a UL 508A Listing for your industrial control panels. Some include: ensuring compliance with globally recognized safety standards, increasing customer confidence in your products, maximizing market opportunities, facilitating inspection, and preventing panel rejection.
Types of UL 508A Control Panel Listing Labels
There are two types of UL Listing labels for industrial control panels:
- Enclosed Industrial Control Panel
- Open Industrial Control Panel
The two types differ primarily in their design and level of protection for electrical components.
Enclosed Industrial Control Panel
Industrial control panels can be installed in two ways: In an enclosure as “enclosed type” equipment, or arranged onto a mounting panel as “open type” equipment. The enclosed type listing label refers to a complete control panel assembly housed within a protective enclosure. The enclosure provides a barrier between the electrical components and the outside environment, protecting against hazards such as dust, moisture, and accidental contact. Enclosed panels commonly have doors or covers that permit access to the internal components while ensuring safety and adhering to applicable standards.
Open Industrial Control Panel
The Open Industrial Control Panel listing label refers to a control panel assembly where the electrical components are not housed within a protective enclosure. Instead, the components are exposed and accessible without any barrier. Open panels must be installed in an enclosure that is built into the machine or is available at the installation site.
UL 50 Electrical Enclosure Ratings
Type 1 – Indoor Use
Provides basic protection against contact with the enclosed equipment and against falling dirt
A UL 508A panel shop is able to build an industrial control enclosure but is limited to rating the enclosure at Type 1.
Type 2 – Indoor Use
Provides protection against contact with the enclosed equipment, falling water or dirt, and dripping and light splashing of non-corrosive liquids
Type 3 – Indoor or Outdoor Use
Provides protection against contact with the enclosed equipment, falling dirt, windblown dust, rain, sleet, and snow, and will be undamaged by the formation of ice on the enclosure
Type 3R – Indoor or Outdoor Use
Provides protection against contact with the enclosed equipment, falling dirt, rain, sleet, and snow, and will be undamaged by the formation of ice on the enclosure
Type 3S – Indoor or Outdoor Use
Provides protection against contact with the enclosed equipment, falling dirt, windblown dust, rain, sleet, and snow; external mechanisms remain operable while ice-laden
Type 4 – Indoor or Outdoor Use
Provides protection against contact with the enclosed equipment, falling dirt, splashing water, windblown dust, rain, sleet and snow, hose-directed water, and corrosion; will be undamaged by the formation of ice on the enclosure
Type 4X – Indoor or Outdoor Use
Provides protection against contact with enclosed equipment, falling dirt, splashing water, windblown dust, rain, sleet and snow, hose-directed water, and corrosion; will be undamaged by the formation of ice on the enclosure
Type 5 – Indoor Use
Provides protection against contact with enclosed equipment, falling dirt, settling airborne dust, lint, fibers, and flyings, dripping and light splashing of non-corrosive liquids
Type 6 – Indoor or Outdoor Use
Provides protection against contact with enclosed equipment, falling dirt, rain, sleet, snow, hose-directed water, corrosion, and the entry of water during occasional temporary submersion at a limited depth; will be undamaged by the formation of ice on the enclosure
Type 6P – Indoor or Outdoor Use
Provides protection against contact with enclosed equipment, falling dirt, rain, sleet, snow, hose-directed water, corrosion, and the entry of water during prolonged submersion at a limited depth; will be undamaged by the formation of ice on the enclosure
Type 12 – Indoor Use (for enclosures without knockouts)
Provides protection against circulating dust, falling dirt, lint, fibers, flyings, dripping and light splashing of non-corrosive liquids, light splashing and seepage of oil and non-corrosive coolants
Type 12K – Indoor Use
Provides protection against contact with the enclosed equipment, dust, dirt, fiber flyings, dripping water, and external condensation of non-corrosive liquids
Type 13 – Indoor Use
Provides protection against contact with the enclosed equipment, lint, dust seepage, external condensation, and spraying of water, oil, and non-corrosive liquids
For proper enclosure selection, an enclosure’s rating is important to consider along with application requirements and environmental considerations
Addition to UL 508A – MTR Program
What is the Manufacturer’s Technical Representative (MTR) Program?
The MTR program relates to a provision added to the UL 508A Industrial Control Panel (ICP) Shop Program requiring UL 508A Listed panel manufacturers to maintain a certified manufacturer’s technical representative on staff. This requirement is designed to ensure there is at least one employee at each manufacturing location who can effectively interpret and accurately apply the requirements of UL 508A to control panel design and manufacturing.
MTR Certification Requirements
MTRs must complete a certification course, pass a certification exam, and recertify every three years.
How Does the MTR Program Help Me?
In order to receive authorization to apply the UL Listing Mark, panel manufacturers must complete mandatory training on the UL 508A Standard when they enter the UL Industrial Control Panel (ICP) Shop Program. However, after the initial training is completed, there are no ongoing requirements for training. Over time this means that as staff turnover and other events occur, panel manufacturers could be left with no staff formally trained on the UL 508A Standard. Methods for addressing this issue vary across manufacturers.
The MTR program is designed to ensure panel manufacturers maintain UL 508A-qualified staff.
If a customer’s engineering team is completing the company’s control panel design, customers may find the MTR course helpful as it can help eliminate mistakes that can delay manufacturing and drive unforeseen costs.
“Qualification as an MTR provides the manufacturer, UL and code authorities the confidence that qualified, competent staff are engaged in the design and manufacture of industrial control panels bearing the UL Mark.”
Tony Robertson, Program Manager, Energy and Industrial Automation at UL
Conclusion
Based on the safety rules recommended by the NEC, industrial control panel manufacturers follow UL 508A for guidance in various areas of design and assembly, including proper component selection, calculation of short circuit current ratings, and wiring methods. The safety guidelines prevent various hazards such as electrical shock, short circuits, overheating, arc flash, and fire hazards. In addition, the standard includes specifications to ensure that industrial control panels can endure environmental factors such as dust, moisture, temperature fluctuations, and corrosion.
