Selecting Components for UL508A Control Panels

Selecting components for UL508A industrial control panels can seem difficult, but knowing these methods makes it easy.

There are several ways to go about selecting hardware that is listed for use in a UL508A enclosure.  Every device that is UL listed has 2 pieces of information attached to it.  The Category Control Number (CCN) and the E-file number.  Each piece of information can be used to select listed parts or confirm if a part is listed.

Selecting A UL508A Compliant Device

So, you know you need a piece of hardware and that it needs to comply with UL508A, but where do you start? This is where CCN’s are the most help. The CCN indicates the category or standard the part is listed for (Ex. NMTR, NRAQ, QQFU2). There are 4 different types of CCN’s:

  • XXXX – UL listed for use in the U.S. and comply with U.S. NEC requirements.
  • XXXX7 – UL listed for use in Canada and comply with the CSA standards.
  • XXXX2 – UL Recognized for use in the U.S
  • XXXX8 – UL Recognized for use in Canada.

Included in UL508A documentation is the Supplement A (SA) table which lists all the CCN’s that are applicable to UL508A. This table can be found at Keep in mind, UL Recognized components are considered incomplete and therefore the notes column of the SA table must be referenced for special instructions. To find the CCN for the device being selected, look through or search the various categories (power supplies, enclosures, relays, etc.) in the SA table to find a CCN that fits the need. Then go on UL’s Product iQ website and search using the selected CCN. This will bring up a list of all the manufacturers that have products that are listed to the searched CCN. The draw back is that some of the CCN’s are fairly broad and cover various types of hardware, but at this point a manufacturer can be contacted with the confidence that they have a part that complies.

Evaluating A Device for UL508A Compliance

The other common scenario is having a part number, but not knowing for sure if it is UL listed and if that listing is acceptable for use under UL508A.  There are 2 ways to confirm a parts listing.

    •  Search for the part number or a portion of the number on the UL Product iQ site.  However, this can prove difficult as parts can be documented in listing files in various forms (partial number, model number, generic manufacturer series, etc.
    • Get the E-file number from the manufacturer directly.  A manufacturer is given an E-file number for each CCN they have hardware listed to.  E-file number can be searched on the UL Product iQ site, which will provide the CCN of the part being evaluated.  The CCN can then be looked up in the UL 508A SA table and any special requirements can be addressed.  Unfortunately if a manufacturer does not have an E-file number, the component is considered to not be listed.  There are ways to use un-listed products, but that is a story for another day.

One of These Things is Not Like the Other

One of the most common assumptions I see made is that National Electrical Manufacturer’s Association (NEMA) is interchangeable with UL. NEMA standards are self-declared by manufacturers and the testing requirements are not always as stringent as UL’s. So, beware of any product that only declares itself as NEMA compliant and does not have an equivalent UL E-file to go with it. For example, wire ways. Many wire ways are NEMA 12 environment rated. However, they are only UL Type 1. So, any UL508A enclosure intended to be used with a wire way attached can be listed, although its environmental rating is limited to UL Type 1.

In Summary (aka TLDR)

All in all at the end of the day, picking parts for a UL508A listed industrial control panel can be simple. Category control and E-file numbers compared to the table at indicate what devices can be used. When CCN’s and E-file numbers cannot be found, reaching out to manufacturers to get those numbers for comparison to the table is the best approach. Manufacturers will know the listings and intended uses of their products.