Blake:
Thanks for sharing the data sheet. The document applies to DC PV systems, however, and I believe the discussion pertains to the AC inverter output. Therefore the bulletin you attached does not apply here. (Note also that this data sheet indicates you need to use two poles for any application, ungrounded or grounded. I believe that requirement was usurped later on for Square D Heavy Duty switches, but again, that is for a different application.) I looked again at Square D general and heavy duty safety switches rated at 30 Amps and I could not find any reference that these switches are continuous duty rated. I still believe that for the application described, the 125% rating has to be applied. If, hypothetically, you could find a 30A disconnect that was continuous duty rated, if it is fed by a 40 Amp breaker, as I believe would be required, then the 30 Amp disconnect is still not suitable. You can not feed a 30 Amp rated device with more than 30 Amps. Bottom line, a 30 Amp disconnect will not meet code on the described project. William Miller Miller Solar 17395 Oak Road, Atascadero, CA 93422 805-438-5600 www.millersolar.com CA Lic. 773985 Quote of the month: “As they age, batteries transition from energy storage devices to energy consuming devices.“ W. Miller *From:* RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *Blake Gleason *Sent:* Wednesday, August 21, 2019 4:20 PM *To:* RE-wrenches *Subject:* Re: [RE-wrenches] 30 amp disconnect/40 amp breaker Typically a fused disconnect can only handle 80% of it's nominal current on a continuous basis. Unfused disconnects are often 100% rated. For example, see attached Square D bulletin #3110DB0401R0410. So, a 100% rated (unfused) 30A disconnect (at least, from Square D) should be fine here, as long as your OCPD is provided elsewhere (eg, the breaker you mentioned). NEC 690.8(B)(1)(Exception) explicitly allows a 100%-rated device to be used without multiplying the inverter output current by 125%. On Wed, Aug 21, 2019 at 3:22 PM Greg <g...@remotepowerinc.com> wrote: Fellow Wrenches, I'm having a discussion with a utility engineer regarding the following situation: Installing a 6kW inverter that has a full rated output of 25 amps. 80% of 30 is 24. That means to me I need to go up to a 40 amp breaker. I'm running #8 (continuous load 25 x 1.25 etc.) The engineer believes I should use a 60 amp disco since it's on a 40 amp breaker. My thinking is I can use a 30 amp disco since it can not produce more than 25 amps ever. Do any of you have a reference that shows what I'm doing is okay? Not okay? Thanks again, Greg Egan Remote Power Inc. _______________________________________________ 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 -- *Blake Gleason, PE* | Employee-Owner | *Director of Innovation & Technical Excellence* 510.845.2997 x128 Follow us on Facebook <https://www.facebook.com/pages/Sun-Light-Power/119675658118322?ref=hl>, LinkedIn <https://www.linkedin.com/company/sun-light-and-power> or our website <https://sunlightandpower.com/>.
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