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?
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?