Rapid Shutdown with 128 Cell PV Module

[msheets]

I am validating a preliminary rooftop PV system design for a potential client and found something that I haven't had to consider before. Their preliminary design calls for a 128-cell PV module with a rated Voc of more than 90 V. Given the requirements of NEC 2017 690.12 that the conductors inside the array boundary be limited to not more than 80 V, can this module be installed on the roof of a building? I have reviewed all the relevant information I could find from the manufacturer, and it doesn't give any indication one way or the other, though the only promotional photos I've seen of these particular modules have been ground-mounted systems.

Thanks.

 

[Carultch]

The 80V limit rules this module out of this application. Without the AHJ providing an exception to the 80V limit, its use is limited to non-buildings or where NEC2014 applies.

At one point, there was a "VC" version of this module, that limited Voc to always be 80V and less. I'd like to see it come back, so it could be a viable option for use on buildings.

 

[msheets]

The 80V limit rules this module out of this application. Without the AHJ providing an exception to the 80V limit, its use is limited to non-buildings or where NEC2014 applies.

At one point, there was a "VC" version of this module, that limited Voc to always be 80V and less. I'd like to see it come back, so it could be a viable option for use on buildings.

That is what I suspected. Even with module level controls, it still exceeds the 80V limit. Hypothetically, if the MLPE were installed so as to eliminate the leads entirely, would it then be compliant?

 

[pv_n00b]

If you used an integrated MLPE it would probably pass, but an add on MLPE still has conductors from the module to the MLPE that could be above 80V. There has always been a discussion on if this 80V limit applies internally to the module since if the module is damaged that could expose a bit of conductor at more than 80V. Modules that have a Voc over 80V were not considered appropriate for roof installation when designing the RSS requirements.It was assumed they would stay in utility-scale ground mounts. You can also wait for UL 3741 to come out and hope someone makes a listed system using these modules.