I checked the math and it indeed seems like a rounding issue – 20,000 W / 480 V / √3 = 24.05626122 A
I wonder if the SMA tech support agent that Brian spoke with was just reading the manual when they said it was 24.1 A. Regardless, it seems like we would need to rely on the manufacturer to clarify their intent when the nameplate and manuals don’t match up. I had been taught to rely on the nameplate right on the device when all else fails. Hopefully no one has a situation where this actually matters! August Luminalt *From:* RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *Garrison Riegel *Sent:* Thursday, September 01, 2016 6:39 AM *To:* RE-wrenches *Subject:* Re: [RE-wrenches] SMA Tripower Hi Brian, Can we not invoke Art. 220.5(B) Fractions of an Ampere to round down to a 30A OCPD in this case? I suppose that .1 could be pretty significant when combining many of these inverters. Garrison Riegel Solar Service Inc On Aug 31, 2016, at 11:24 PM, Brian Mehalic <br...@solarenergy.org> wrote: Hey Wrenches- Just a heads up on the SMA Tripower - I like the inverter, but you gotta read the install manual! Spec sheet says 24 A continuous output current for the 20 kW Tripower. Install manual (and tech support) says 24.1. That extra .1 A takes you from a 30 A to a 35 A breaker. Of course you should follow the install manual not the specs. But what about the label on the side of the inverter? Well I've seen more than a handful that are labeled with a flat-out 24 Aac output current. What's an installer or inspector to do besides hope mfg's can get their numbers in order? Upon closer examination, most of the STPs are 0.1 A higher than their spec sheet per the install manual - it doesn't really make a difference on the 12 or 15 kW models - just the 20 where you have to go up 1 standard OCPD size. Pretty sure there's lots of 20 kW units out there backfeeding a 30 A breaker. Hmmmmm.... Brian Mehalic NABCEP Certified Solar PV Installation Professional™ R031508-59 520.204.6639 Solar Energy International http://www.solarenergy.org SEI Professional Services http://www.seisolarpros.com _______________________________________________ List sponsored by Redwood Alliance List Address: RE-wrenches@lists.re-wrenches.org Change listserver email address & settings: http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org List-Archive: http://www.mail-archive.com/re-wrenches@lists.re-wrenches.org/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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