Hi Glenn, I don't completely agree with your interpretation of ESS systems and the application of Article 706. Yes, an ESS *could* provide 120/240 VAC (e.g. the Powerwall), but the figures in Article 690 show three different configurations where the output of the ESS is not AC, and where the ESS disconnect comes before any power electronics (like a multimode inverter, as shown in the AC and DC coupled systems) or loads (as shown in the stand-alone system). Are those ESS connected to other systems which utilize stored energy to provide AC power? Yes, but the key is "connected to other systems" - in many cases the ESS only provides DC. In fact the definition of ESS clearly states this - it *can* have AC or DC output, and it *may* include power electronics (but may not).
My understanding is that the 60 volt limit (which is obviously problematic in a world where 48 VDC batteries and ESS are very common) was inserted in order to exempt other devices that store energy (such as UPS, or battery backup in fire alarms/exit signage/etc.) from the 706 requirements. Cheers, Brian Mehalic NABCEP Certified Solar PV Installation Professional™ R031508-59 National Electrical Code® CMP-4 Member (520) 204-6639 Solar Energy International http://www.solarenergy.org SEI Professional Services http://www.seisolarpros.com On Sat, Mar 9, 2019 at 4:07 PM Glenn Burt <[email protected]> wrote: > Hi Ray, > > This is a conversation I have had some time ago with a number of my fellow > inspectors and code experts. When the 2017 NEC came out, I agreed with Mike > Holt and Bill Brooks' assessment that the new article was poorly written > and did not apply to most systems being installed today. After much > discussion through my Cadmus network of authorities, it emerged that indeed > 706 apples to the typical residential systems. > So Energy Storage Systems (ESS) are the point of article 706, and I > believe that the key point is that the SYSTEM is generating AC voltage of > 120VAC or 240VAC, making the system fall under article 706. > > Batteries themselves are minimally covered by NEC 480, NFPA 1, and the IFC > as applicable locally. > So, the bottom line is that the new article does cover the work we do when > systems provide or interface with 120VAC or above (making the system > operation exceeding the 60V AC trigger). > > My initial problem was believing that the article applied to a component > (the battery bank), and not the system (all components taken together as a > generator/storage system). It is an easy misunderstanding to make. > > Hope this helps! > > -Glenn Burt > > -----Original Message----- > From: RE-wrenches <[email protected]> On Behalf > Of Ray > Sent: Saturday, March 09, 2019 12:41 PM > To: RE-wrenches <[email protected]> > Cc: Bill Brooks <[email protected]>; Bill Brooks <[email protected]> > Subject: [RE-wrenches] NEC for Batteries < 60v ?? > > Hi Everyone; > > I'm updating all my verbage on plansets, and I just realized that the > newly created article 706 covering Energy Storage Systems is only for Over > 60 VDC (706.1) Also article 480 for batteries only requires disconnecting > means over 60 VDC ?! (480.7). I'm not about to not have a disconnect, so > now that NEC pulled battery systems out of 690, where do we go for > guidance on normal battery systems: 12, 24, 48 VDC? > > Overall, I welcome most of the changes in NEC 2017, like separating off > grid systems into articles 706, and 710, but it seems us off grid > installers need some more clarification. > > Thanks, > > -- > Ray Walters > Remote Solar > 303 505-8760 > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: [email protected] > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://www.mail-archive.com/[email protected]/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > > > _______________________________________________ > List sponsored by Redwood Alliance > > List Address: [email protected] > > Change listserver email address & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://www.mail-archive.com/[email protected]/maillist.html > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out or update participant bios: > www.members.re-wrenches.org > >
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