Listed Disconnect for PV applications, NEC 690.17, UL, ETL

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MechEdetour

Member
Location
NY, USA
Riddle me this.

According to 690.17(A), there's quite a list of various disconnects that can be used and be compliant with that particular section of the article. Really anything from listed PV switches marked for PV systems to Listed DC rated enclosed switches.

Let's say a system designer is at the point where he/she needs to spec a disconnect for the PV system. With what is allowed per 690.17(A), a switch that is listed to UL98B and installed in any enclosure would satisfy this requirement. Correct? Now, a listed switch bought with the enclosure from a manufacturer (as an assembly) and listed to UL1741 would also satisfy this requirement. Correct?

If both these are true, why would someone go through the hassle of finding an assembly that is listed to UL1741 when they can just use a switch listed to UL98B, place it in an enclosure, and still meet the requirements of 690.17(A)?

Now a second "question" that is somewhat related,

When UL evaluates an assembly for listing to UL1741, they require that a switch also be listed for the use. So technically a UL98B switch with the proper ratings would need to be used in a disconnect assembly to be listed to UL1741 with the same use/ratings. ETL however, as I know it, does not require the switch to be listed to UL98B when the assembly is being listed to UL1741. Any switch, such as one listed to UL98, or even to IEC standards can be used so long as it meets all the criteria in the outline for UL1741. (Which by looking at PV equipment on the market, vast majority is listed by ETL and not UL. Seems like everyone went to ETL because there was more lenience with what components they were allowed to use to get their listing. UL would require evaluation to UL98B for the switch, and then UL1741 for the assembly. I can see someone saying screw that and going through ETL to avoid the need for multiple evaluations.)

With that being said, lets take a switch with part number ABC that is rated for 200A at 1000VDC to UL98B. The same switch ABC to some IEC standard is rated for 300A at 1000VDC. ETL will let you use the switch IEC rating of 300A at 1000VDC if that is what it is being evaluated for during testing/evaluation to UL1741.

So in essence, the switch that normally would not be allowed to satisfy NEC requirements for 690.17(A) for 300A at 1000VDC because it isn't listed to UL98B for that rating, can now be used because it is listed to UL1741 for that rating. . .

Is this confusing enough?
 

SolarPro

Senior Member
Location
Austin, TX
If it helps you solve the riddle, this goo all disappears in NEC 2017. Why? Because the Code-Making Panel recognizes that this content belongs in the product safety standards that pertain to PV system components and not in the NEC.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Although I'm not actually familiar with it, my understanding is that UL 1741 is for inverters, so I don't really understand what it has to do with the question. There's that one brand of over-priced DIN-rail j-box that proudly states "Conforms to UL1741" on the box. I chuckle whenever I see that.

I think the intent of the code section was to give AHJs some leverage when people try to use AC switches.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Although I'm not actually familiar with it, my understanding is that UL 1741 is for inverters, so I don't really understand what it has to do with the question. There's that one brand of over-priced DIN-rail j-box that proudly states "Conforms to UL1741" on the box. I chuckle whenever I see that.

I think the intent of the code section was to give AHJs some leverage when people try to use AC switches.
So I would assume that the product has not actually been tested and listed by a NRTL.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
So I would assume that the product has not actually been tested and listed by a NRTL.

No it probably has. Just not to UL1741 because it isn't covered by that product standard. They are trying to give the impression that their j-box is somehow specially appropriate for solar as compared to a bell box or a NEMA4 PVC box, or any other such appropriate box. It's a load of hooey. Perhaps it helps with some AHJs who don't know the difference between a j-box and a combiner. The latter is required to be listed specifically for PV applications, the former is not.
 

MechEdetour

Member
Location
NY, USA
If it helps you solve the riddle, this goo all disappears in NEC 2017. Why? Because the Code-Making Panel recognizes that this content belongs in the product safety standards that pertain to PV system components and not in the NEC.

Yea I came across that too. So a lot of it goes away. But as of now, and since 2014 this goo still needs to be applicable some how.

Although I'm not actually familiar with it, my understanding is that UL 1741 is for inverters, so I don't really understand what it has to do with the question. There's that one brand of over-priced DIN-rail j-box that proudly states "Conforms to UL1741" on the box. I chuckle whenever I see that.

I think the intent of the code section was to give AHJs some leverage when people try to use AC switches.

Inverters, converters, controllers, and interconnection system equipment, etc. Maybe I could have narrowed it down to something a bit more specific. How about a combiner with an integral disconnect? Combiners would be listed to UL1741, and the disconnect selected for it would be subject to what I am asking. . . I could find some examples of PV disconnects listed to UL1741 too.

So I would assume that the product has not actually been tested and listed by a NRTL.

Correct. I am strictly talking about Listed equipment, not anything that "conforms to" "compliant with" or "built to" UL1741 standards.
 
Location
California
I'm not really sure why combiners are listed to UL 1741 other than considering the combiners integral to the whole system. We had an inspector asking for phases and frequency ratings for a combiner box...
 

SolarPro

Senior Member
Location
Austin, TX
Combiners have to be listed to UL 1741 per 690.4(D) (emphasis added):

(D) Equipment. Inverters, motor generators, photovoltaic modules, photovoltaic panels, ac photovoltaic modules, source-circuit combiners, and charge controllers intended for use in photovoltaic power systems shall be identified and listed for the application.

This content appears under 690.4(B) in NEC 2014 with minor revisions:

(B) Equipment. Inverters, motor generators, PV modules, PV panels, ac PV modules, dc combiners, dc-to-dc converters, and charge controllers intended for use in PV power systems shall be listed for the PV application.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Typically where I see words that say "conforms to" or something like that, it means that they really didn't get the product listed...they just built it to what they think the standard says and are trying to make you think it is a listed product.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Typically where I see words that say "conforms to" or something like that, it means that they really didn't get the product listed...they just built it to what they think the standard says and are trying to make you think it is a listed product.

Well then, the mystery deepens, because I looked up this product and the datasheet actually says it is listed by ETL to UL1741. But on the box itself it says 'conforms to.' Maybe they just didn't bother to change the label when they got the listing?

At any rate, just looking at the table of contents for UL1741, I can't figure that more than 5% percent of the product standard might in anyway apply to this j-box. And the NEC does not require PV listing for the purpose this box normally serves. So I just find it comical, that's all.
 

MechEdetour

Member
Location
NY, USA
So to clear up the first part where I was asking why someone would bother with UL1741 vs. any one of the many other options.

For example,

Option 1
Disconnect box Listed to UL1741 (Standard for Inverters, Converters, Controllers and Interconnection System Equipment for Use With Distributed Energy Resources).

http://www.solarbos.com/data/files/26/2015 SolarBOS Load Break Disconnect Enclosure.pdf
http://www.bentek.com/wp-content/uploads/991-003912-000-B-Bentek-MDSS-DS.pdf

Option 2
Use any enclosure, and use a disconnect switch suited for PV systems that is Listed to UL98B (Outline of Investigation for Enclosed and Dead-front Switches for use in Photovoltaic Systems). Or even a switch that is just Listed to UL98 (Enclosed and Dead-Front Switches).

Either of the two switches satisfy 690.17(A). Specifically, UL98B switch would meet 690.17(A)(4) and UL98 for 690.17(A)(8) so long as it's applied within its rating.

https://library.e.abb.com/public/9e11163ebee48f00c1257d710049c400/1SCC301014B0201.pdf
http://www.socomec.us/files/live/sites/systemsite/files/DOCUMENTATION/SCP_hors_cata/dcg_152033us.pdf

I included a few examples to show that the options I speak of, do exist. And there are many others. . .

So.

I don't understand why manufacturers would go through the hassle of listing their disconnect boxes to UL1741, when requirements for disconnects for PV systems can be satisfied by just offering enclosures with disconnects Listed to UL98, UL98B, etc.

Am I right or am I right? If an AHJ challenged a disconnect box that isn't listed to UL1741, seems like it'd be easy to prove that it doesn't need to be so long as it meets the requirements of one of the many other alternatives. . .
 

SolarPro

Senior Member
Location
Austin, TX
As long as the "disconnect box" isn't a "combiner box," I'd agree with you. But if the "disconnect box" is a recombiner or subarray combiner, the Code is pretty clear that these need to be listed specifically for PV applications. The UL product safety standard that applies to dc combiners is UL 1741.

Put another way, the SolarBOS and Bentek products need to be listed as an assembly to UL 1741 because these are dc combiner boxes. In all likelihood these recombiners use recognized components, like the ABB switches you link as disconnecting means. These individual switches do not need to be listed to UL 1741 to be part of an assembly that is listed to UL 1741.
 

MechEdetour

Member
Location
NY, USA
Well then, the mystery deepens, because I looked up this product and the datasheet actually says it is listed by ETL to UL1741. But on the box itself it says 'conforms to.' Maybe they just didn't bother to change the label when they got the listing?

At any rate, just looking at the table of contents for UL1741, I can't figure that more than 5% percent of the product standard might in anyway apply to this j-box. And the NEC does not require PV listing for the purpose this box normally serves. So I just find it comical, that's all.

I always just go for the CoC from UL or ATM from ETL (I think that's what ETL issues). Manufacturers should have that readily available. It shows what the product is listed to if at all. People use words interchangeably all over the place without realizing each one has a specific meaning or no meaning at all. . . "listed" "recognized" "certified" "conforms to" "compliant with" "constructed to" "classified" and so forth. . .
 

Carultch

Senior Member
Location
Massachusetts
I always just go for the CoC from UL or ATM from ETL (I think that's what ETL issues). Manufacturers should have that readily available. It shows what the product is listed to if at all. People use words interchangeably all over the place without realizing each one has a specific meaning or no meaning at all. . . "listed" "recognized" "certified" "conforms to" "compliant with" "constructed to" "classified" and so forth. . .

How is anyone supposed to be able to keep track of this vocabulary anyway? It seems like every day there's a new past tense verb that goes with all these different testing agencies, and no easy way to look at a datasheet to get a straight answer for "CAN I USE IT OR CAN I NOT USE IT?". Instead, you just end up in an endless semantics debate.
 

MechEdetour

Member
Location
NY, USA
It's loopy for sure.

Recognized, Listed, Classified, and now Certified are the official designations per UL. All the others are ways people try to convey their third-party evaluation, or suck you into thinking something is third-party recognized, listed, etc.

Just gotta look for that Mark and Certificate!
 

GoldDigger

Moderator
Staff member
Location
Placerville, CA, USA
Occupation
Retired PV System Designer
Don't know if it is common anymore but in consumer goods you used to see the UL sticker on the power cord, applying to the cord only, the appliance never having even been tested.
 
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