Confused over "Listed" Surge-Protective Devices

[Shackled Designer]

According to the NEC (2014), "285.5 An SPD shall be a listed device."

My first point of confusion is the scope. Since article 285's scope covers "surge-protective devices (SPDs) permanently installed on premises wiring systems of 1000 volts or less," would someone clarify whether this includes industrial panels? I know that the definitions in Article 100 seem to distinguish industrial panels from premises wiring, but there does seem to be some overlap. On the other hand, in my thinking, the most obvious understanding of premises wiring would be power/signal wiring inside and outside a building as opposed to that which is inside an industrial panel. Is that right, or is it an over-simplification?

My second problem relates to interpreting what UL might mean about listing on its own website concerning SPDs. Regarding SPDs of type 1, 2, and 3, UL1449 indicates that "These devices are listed." However, I have in my possession a Type 2 SPD that is labeled with the "Recognized" symbol instead of the "Listed" symbol, and I have found at least two more from other manufacturers also selling in the U.S. that also list both of their Type 2 devices as UL-Recognized and not listed. So my question is this: what does UL1449 mean when it states that Type 2 SPDs "are listed," given the fact that I can get several SPDs of that type which indicate that they are merely recognized?

What all this boils down to is whether it matters if I use an SPD that is labeled as recognized in an industrial panel. Common sense tells me yes, but I figured I should run these questions through a multitude of counselors first.

Kind regards,
The Shackled Designer

 

[mgookin]

I'll address the difference between "listed" and "recognized" for you.

Listed means it's been tested and approved by a nationally recognized testing laboratory (NRTL) for stand-alone use. An example is your refrigerator. You plug it in and use it without reliance on anything else.

Recognized means it's been tested and approved by a NRTL for use in a listed assembly when used within the specifications for the comonent, product or device. It's not intended to stand alone, but it's intended to be a component of a listed assembly. If you are a panel shop and you're building panels, you will be using "recognized" components to make your "listed" panel.

 

[Shackled Designer]

Thanks, mgookin.

Your explanation strengthens the distinction in my mind between industrial panels and premises wiring.

Thinking further about this subject, I realize that there is at least one exception to the allowance of "recognized" devices on a panel that is to become UL listed: where branches coming from a feeder line on the panel are protected by circuit breakers, a UL489, listed breaker is usually required. This requirement seems fairly clear from the perspectives of the NEC and NFPA 79.

I am still puzzled by the UL statement about SPD types 1 through 3 all being listed devices, however, but to be fair this is an NEC forum, not a UL forum. Since I initiated this question, however, I'll try to follow up with information I receive if my contact at UL responds.

Kind regards,
The Shackled Designer

 

[mgookin]

You can also contact the manufacturers of those products for assistance.

I'm not a "panel guy" but there are many around here, and there are also many people on here much more versed on the NEC than I am.

Can anyone else interject here?

 

[Shackled Designer]

I believe I have discovered the answer to my question.

UL makes a distinction between what it calls either "permanently connected SPDs" or "point of utilization SPDs," both of which are listed devices, and component assemblies, which are merely recognized devices. All of these can be designated for Type 1, 2, or 3 applications. So your distinction, mgookin, between listed and recognized devices seems to correspond with UL's break between the two categories. What I have been looking at are evidently component assemblies.

My contact at UL points out that recognized SPDs, as all recognized devices, "will typically have a stated criteria for use, identified as Conditions of Acceptability . . ." So, presumably, as long as the recognized SPD is used in a manner that meets this criteria, it would be acceptable to UL as a panel component.

Thanks for the input on this question. If anyone has any more to offer, please feel free . . .

Regards,
The Shackled Designer