Mayfield Renewables Code Corner: 2023 UL 9540 Listing and 9540A Testing 

Excellent question! The UL9540 listing certainly can apply to off-grid systems, but it is not required. NEC articles 706 (Energy Storage Systems) and 710 (Stand-Alone Systems) call out equipment listings, but there are multiple ways to comply. If a manufacturer has listed the *entire system* to UL9540, as it looks like this manufacturer has done with some products, then yes, all the listing requirements would be applicable. The updated standard does require the ESS to "employ an enclosure of non-combustible materials." Essentially requiring metallic enclosures. It would be up to the listing agency to deem what enclosure that applies to (cell, module, or unit). Therefore, the case holding all the modules may not be required to be metallic if the individual units are in a non-combustible material and properly evaluated for (lack of) fire propagation. It is also possible to use a non-UL9540 system by installing listed components together by complying with Articles 480 and 705 for an off-grid system (as well as other articles as applicable).

Thanks for asking this! Of the 20+ cut sheets submitted to my AHJ the solar plan reviewer noticed the EG4 6 space rack spec sheet was missing. I asked EG4 and there is indeed a manual. Hopefully the AHJ is okay with this “metal enclosure” - it’s only “listed with” in ESS context for UL9540 the 18kpv but I’m using two 6000XP. I guess this means it’s not a listed ESS. But is it okay without the rack? Seems very dangerous. The code is so confusing. My suspicion is that it was driven by profit and not safety. Tesla and utility lobbyists have their hands all over the code and it’s becoming a problem.

We built an off grid cabin, we are having a bad time trying to find a system that is certified. We are in ontario Canada and we can seem to get a straight answer from anyone including the inspector. Feeling lost.