UL3741

G

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Consulting Electrical Engineer - Photovoltaic Systems
I have never invoked UL3741 but I now have a customer who is requesting it. I am using Unirac RM5 racking with SMA Core1 inverters, and Unirac touts their compliance with the standard on their website. My question is this: If I place the inverters within one foot of the arrays they serve and I run all the DC conductors through the one foot gaps, am I done with UL3741 compliance? I have called Unirac several times but I have not been able to get an answer.
 
ggunn said:
I have never invoked UL3741 but I now have a customer who is requesting it. I am using Unirac RM5 racking with SMA Core1 inverters, and Unirac touts their compliance with the standard on their website. My question is this: If I place the inverters within one foot of the arrays they serve and I run all the DC conductors through the one foot gaps, am I done with UL3741 compliance? I have called Unirac several times but I have not been able to get an answer.
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Apparently, no one else knows, or else my question has exposed me as being so incompetent that no one will stoop to answering my question. I don't know which to wish for. :D
 
ggunn said:
... If I place the inverters within one foot of the arrays they serve and I run all the DC conductors through the one foot gaps, am I done with UL3741 compliance? ...
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I think, as the engineer, you are also required to put a large-font-size note in bold on each page of the plans, stating precisely what docs the installer has to follow to make you done. 😉
 
UL3741 to me seems to cover items mentioned in 90.2, like the installation of electrical equipment and raceways, not like the normal UL product standard.
Almost like a alternate solar installation code to 690 that you can do under an engineers supervision.
I have never worked on nor seen such a system, it would be interesting to see one, seems like having more options is good.
 
One thing that concerns me is how one can prove that a UL3741 PV system would do what it is supposed to do.
 
ggunn said:
One thing that concerns me is how one can prove that a UL3741 PV system would do what it is supposed to do.
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Not your problem as the EOR. 😉 Just cite all the UL and manufacturer documentation and give instructions to follow it to a T.

The idea is that it has been proved to an NRTL. I agree somewhat with tortuga's comment but we are also still talking about instructions that are specific to a manufacturer's particular product.
 
tortuga said:
UL3741 to me seems to cover items mentioned in 90.2, like the installation of electrical equipment and raceways, not like the normal UL product standard.
Almost like a alternate solar installation code to 690 that you can do under an engineers supervision.
I have never worked on nor seen such a system, it would be interesting to see one, seems like having more options is good.
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It's more like 'additional' than 'alternate'.
 
electrofelon said:
Well isnt going thru the process of getting the system certified to the standard what assures that?
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How does one do that for a particular system? Does someone inspect it and green tag it after it is completed? I don't think so but I could be wrong.

Have any of us designed and built a UL3741 compliant PV system? If so, please speak up.
 
ggunn said:
How does one do that for a particular system? Does someone inspect it and green tag it after it is completed? I don't think so but I could be wrong.

Have any of us designed and built a UL3741 compliant PV system? If so, please speak up.
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I did get a quote from unirac on one, but the project fell thru after that.

While i admit i dont know the specifics of what design requirements and aspects go into designing a racking system to comply with UL3741 (isnt it mostly non metallic?) someone has thought it thru and if it meets the standard than the NEC has decided that rapid shutdown is not required. Sorry to be blunt, but what is so hard to understand about that? 😉
 
electrofelon said:
I did get a quote from unirac on one, but the project fell thru after that.

While i admit i dont know the specifics of what design requirements and aspects go into designing a racking system to comply with UL3741 (isnt it mostly non metallic?) someone has thought it thru and if it meets the standard than the NEC has decided that rapid shutdown is not required. Sorry to be blunt, but what is so hard to understand about that? 😉
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I have the same question I started with. For a Unirac RM5 racking system is all I have to do is install the inverter within 1 foot of the array and I'm done? I haven't been able to get Unirac to tell me.
 
jaggedben said:
The AHJ does?
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Is an AHJ likely to know enough about UL3741 to make that determination? Should I just tell them that is is compliant and let them prove me wrong? :D

Unirac does have a page that has links to UL3741 installation guides for their different racking systems but the link for RM5 gets an "Oops! That page can’t be found" msg
 
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It seems one starts by determining the hazard level in a unfaulted array, then the faulted array.
Appendix F has examples.
ggunn said:
Is an AHJ likely to know enough about UL3741 to make that determination? Should I just tell them that is is compliant and let them prove me wrong? :D
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Yeah I think the EE or designer in essence bears all the liability, so they should take your word.
 
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