UL 508 and UL 508A are standards for industrial electrical equipment that apply to operation in the United States and Canada. They were developed by Underwriters Laboratories (UL), the world’s leading provider of safety standards testing and certification.
The two standards cover different areas: UL 508 is the standard for the safety of industrial control devices. It covers industrial control devices and device accessories with a rated voltage of 1,500 volts or less that are used to start, stop, regulate, control, or protect electric motors. UL 508A is a subset of UL 508 and applies specifically to industrial control panels (Industrial Control Panels). While the UL 508A standard is up to date, the UL 508 standard is obsolete. It was gradually phased out between 2012 and 2017 and replaced by UL 60947.
Can you choose between UL 508 and UL 508A?
For some products, there is overlap, and certification is possible under both UL 508A and UL 508. In these cases, specific details such as the application and requirements determine which standard the product is built to and certified under. However, industrial control panels must always be certified to UL 508A.
The UL 508A standard specifies the guidelines for industrial control panels in detail and defines how the connections, fuses, and protective devices used must be designed to comply with the UL 508A standard.
UL 508 vs. UL 508A
There are several important differences between the two standards, UL 508 and UL 508A:
- The UL 508A standard applies to control cabinets and control devices with an operating voltage of up to 600 volts. The UL 508 standard applies to a rated voltage of 1,500 volts.
- If a product is certified to UL 508A, the manufacturer may modify it as desired, as long as the manufacturer uses components that are already“UL-listed.” In addition, the design and manufacturing must comply with the requirements of the UL 508A standard. In contrast, a product certified to UL 508 can no longer be modified. It can only be put into service in the configuration in which it was certified.
- Another difference concerns the enclosure: for Industrial Control Panels, the enclosures are referred to as control cabinets or control panels. These must be accessible via a door or a special panel. If products are built and certified to UL 508, the enclosures do not have to be accessible to the user.
- Article 409 of the National Electrical Code (NEC) addresses industrial control panels and refers to the UL 508A standard. This gives the standard the force of law. UL 508 is not mentioned directly in the NEC.
- Article 409 of the National Electrical Code (NFPA 70) requires that industrial switchboards be marked with their short-circuit current rating (SCCR). This value must be based on that of a listed and certified assembly, or another appropriate method must be used to determine the value. (Further information on determining the SCCR of industrial control panels in accordance with UL 508A can be found directly on the UL website.)
Thus, while UL 508A requires that the short-circuit current rating (SCCR) be specified for industrial switchgear, UL 508 does not require this for auxiliary products, for example. - Another difference lies in the protection of the internal electrical circuit. This protection is required for industrial control panels, but not for UL 508 certification.
The following table summarizes the differences:
How do you write UL 508 and UL 508A correctly?
As with all details, UL is very precise about spelling as well. All designations are written with a space after UL. So UL 508 and UL 508A. Spellings such as UL508, UL508A or UL 508 A are not correct. Nevertheless, UL508, UL508A and UL 508 A keep appearing.
Are you exporting your machine to the U.S. or Canada?
In the U.S. and Canada, strict safety standards and regulations apply that differ fundamentally from those in Europe. For example, the UL 508A standard applies to industrial control panels in all operating environments except hazardous locations. However, a certified control panel is only one part of the overall process. Many companies are daunted by the time-consuming and complicated export process and therefore choose to forego these lucrative markets.
But there is a simple and convenient solution: If you want to export your machinery and systems to the USA or to Canada, Krayer and its partners will handle the entire export process. You can find out more in our article “Across the pond in four steps”.
Transition: UL 60947 replaces UL 508
UL 508, the standard for industrial control equipment, has been harmonized with the essential product standards of the IEC standard for low-voltage switchgear, IEC 60947. The transition took place in three phases between 2012 and 2017.
The goal of this harmonization was to establish standards based on and incorporating IEC requirements, while at the same time allowing for sufficient national variations to facilitate the transition from UL 508 to UL 60947-4-1A. This goal has been largely achieved.
The UL 508 and UL 60947 series of standards do not look the same. However, when the national differences included in the harmonized standards are taken into account, they are essentially technically identical.
