What is UL Standard 508A?

UL508A is the UL standard for the construction of Industrial Control Panels. This document gives guidelines to panel builders on various issues including proper component selection, wiring methods and calculation of short circuit current ratings. If a customer follows UL508A’s construction requirements and recommendations, they can apply to have their panel listed by UL. Upon successful inspection, the panel would bear the UL label.

What is the impact of NEC 2005, Article 409?

The intent of Article 409 is to prevent the misapplication of control products and related equipment. This article will provide the minimum requirements to ensure safe installation and inspection of industrial control panels. Article 409 covers industrial control panels that are intended for general use and operate at a voltage of 600V or less. The entire panel and all components inside will be required to meet a defined Short Circuit Current Rating (SCCR) for the application, and the panel will have to be marked with the appropriate SCCR. The marking requirements of UL Standard 508A Industrial Control Panels for SCCR ratings took effect in April 2006.

What does a UL Listed Industrial Control Panel label signify?

A UL label signifies that the panel builder has met the requirements of UL508A, and that their panels are subject to inspection by UL field representatives. Not every panel is inspected by UL, but panels are subject to inspection by UL depending upon the quantity of UL Labeled panels made in a give time period. A UL Follow Up Services representative inspects the facility and reviews the panels to the UL508A Procedure for the particular panel shop being inspected. If the panels are found to be in compliance, they are permitted to continue production and apply the UL Label.

How do I obtain the SCCR for a panel I am building?

There are three options:
1. Purchase previously tested combinations from a major supplier that can be tabulated in the panel builder’s procedure. Eaton is a major component supplier that is committed to providing this information to our customers. Once you have all of the component ratings, either use an outside service or UL508A Supplement SB.
2. Test each panel construction and record the construction in a follow-up procedure. With the numerous possibilities for product combinations within a panel, this option will require a tremendous investment in testing and maintenance. The test has to be witnessed by a UL project engineer.
3. Utilize the method described in UL508A Supplement SB.


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