Goodbye UL 508: A Transition More Than a Decade in the Making

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When it comes to standards that control panel builders have to abide by, I have an interesting view. On the one hand, I represent Schneider Electric on various standards committees and industry groups, including the National Electrical Manufacturers Association (NEMA). On the other, I work with customers, so I see how the decisions made by standards bodies play out in practice.

Right now there’s a transition underway regarding UL 508 that customers would do well to be aware of. It’s the result of more than 10 years of work by NEMA, UL and others to harmonize international standards from UL and its counterparts including the Canadian Standards Association and the International Electrotechnical Commission (IEC) in Europe.

The story starts some 15 or 20 years ago, at a meeting where a number of manufacturers of industrial control panels made the point that it was time-consuming and difficult for them to test each of their products to the various standards from each region, including UL, CSA, IEC and others in Asia and elsewhere. They made the point that it took longer to complete all the testing for their products than it did to develop and manufacturer them.

The UL representative at the meeting understood their predicament and vowed to try to harmonize the UL 508 standards with the latest IEC standards. And UL , with help from industry representatives like me, has been working on doing just that for a good 10 years.

The UL 508 standard is more than 200 pages long. We formed a committee that went through it paragraph by paragraph to find differences between IEC and UL test protocols. We tried to compare them to see what the differences were, determine whether both methods were acceptable or if one was better than the other. In short, we tried to keep the best of both worlds in the revised standard, while always making safety our primary goal.

The end result is a new series of standards, UL 60947 that are now being phased in. If you haven’t already come across that standard, chances are you soon will.

UL 60947-4-1 is the standard that most closely resembles UL 508. The phase-in plan works like this. Prior to Jan. 26, 2012, products were evaluated to the UL 60947-4 unless the customer specifically requested it be evaluated using UL 508. Between Jan. 26, 2012 and Jan. 26, 2017, new products are to be evaluated to UL 60947-4 only, but revisions to existing products may be evaluated using UL 508 if requested. After Jan. 27, 2017, all products must meet UL 60947-4 specifications.

So what are the big differences between the two standards? Honestly, there’s nothing terribly dramatic. Here’s the official word from an FAQ (PDF) that the UL put together on the transition:

This harmonization work was undertaken with the intent of creating standards that, while being based upon and adopting IEC requirements, would incorporate sufficient national differences to ease the transition from UL 508 to UL 60947-4-1. This goal has largely been accomplished in all cases. While the UL 508 and UL 60947 series standards do not look the same, when taking into account the national differences included in the harmonized standards, they are essentially technically identical.

We did our best to harmonize the UL and IEC standards, but could go only so far because there are intrinsic differences in voltages used around the world. In North America, for example, industrial voltages are 480v at 60Hz while in Europe it’s 400v at 50Hz. Those seemingly small differences are in fact huge in terms of how you test products and qualify them to a standard.

But, within those parameters, we did our best to normalize the standards so manufacturers should have an easier time testing their products against the various iterations.

For customers including panel builders, it’s simply an education process, which is the purpose of this blog post. You’ll need to understand the transition is taking place and what it means when you see a reference to UL 60947 when you were expecting UL 508.

To learn more, check out the UL’s FAQ (PDF) on the transition.