Dave, I looked at the BR24L70RP a while back. It's really a 2-space, 4 cuircuit panel. I think my conclusion was you actually need a single quadplex breaker with common trip center and outer breakers to get (2) 2-pole breaker functionality. The quadplex breakers come in a variety of mixed rating (i.e. 15A center and 20A outer breakers). They are not readily stocked and not cheap. We stuck with Sq D QO load centers for that reason.
Am I missing something? Jason Szumlanski Fafco Solar On Fri, Jun 27, 2014 at 11:32 AM, Dave Click <davecl...@fsec.ucf.edu> wrote: > This is an interesting conversation, but I'm not sure it's going to really > impact anything. > > When an inverter is listed, it is tested with some "maximum output > overcurrent protection" as part of its rating per UL 1741. Typically > inverter manufacturers set this to be just above the inverter's max current > + 25%. As you know, many inverters can work at more than one voltage, so > for the SB5s their max current ratings at 277/240/208V are 18/20.8/24A, > respectively. The max overcurrent protection is 50A. This figure often > appears in the manual but not in the data sheet. For SMA, it's in the > manuals. For some manufacturers, it's only available from tech support. > > For the Sunny Boy line, the only way you could have more than one inverter > on a shared OCPD is if you have two SB5s operating at 277V (18.1A rated > current each, so 2x18.1x1.25 < 50A). The SB6, SB7, and SB8 all have > currents too high to make this work, as they share the 50A max OCPD. The > SB3/3.8/4 have a max OCPD of 30A, which is too low to double-up since each > SB3 requires an OCPD of at least 20A. The TLs don't work either, as the max > for any unit is too low. I don't see it in the SMA manual, but I know that > in other manuals I've seen a manufacturer requirement for a dedicated OCPD. > The only inverters I know of that have a max OCPD rating far beyond their > rated current are micro-inverters. > > As for the shared disconnect, since at least the 2005, 690.15 has noted, > "A single disconnecting means in accordance with 690.17 shall be permitted > for the combined ac output of one or more inverters or ac modules in an > interactive system." That being said, the NEC requires ac modules and > micro-inverters to have ac disconnects (connectors, typically) per 690.6 > and 690.15(A). 690.15 notes that an inverter be able to be disconnected > from all sources, but if doubling up these SB5s you could argue that this > shared disconnect accomplishes that via the anti-islanding protection... so > I agree now that this is a grey area. > > Anyway, it comes down to whether it's worth worrying about this for what > is an extremely small subset of compatible inverter configurations, when > you can just do something like install a $50 Eaton BR24L70RP (70A bus, > 240V, 4 spaces) with two 30A breakers and be on your way. > > DKC > > > > > > On 2014/6/27, 6:53, Richard L Ratico wrote: > >> I may be playing devil's advocate here, but I want to add a few thoughts. >> Jay, I >> just looked at Fronius and SMA inverter data sheets. I found no spec. for >> an >> output OCPD, only a spec for max. output current. >> William, most inverters now come with integrated DC/AC discos. Dave, 2014 >> NEC >> 705.12(D)(1), IMHO, specifies ONE OCPD for the entire interconnected power >> system, not individual OCPD for each inverter. >> >> Generally speaking OCPD is provided for the circuit conductors in a >> system, not >> the individual pieces of equipment. If the equipment manu. specifies >> OCPD, that >> is a different story. >> >> I understand the 2014 code to require appropiate OCPD for all the >> conductors >> from the panelboard to the inverter. If that can be accomlished with one >> device >> at the panel, it meets code. That said, code is a MINIMUM standard. >> >> Bottom line, I agree with Corey that there is no code requirement for >> individual >> OCPD for each inverter. If there is, unfortunately, it is insufficiently >> explicit such that we are having this conversation. >> >> Dick Ratico >> Solarwind Electric >> >> >> --- You wrote: >> I have never seen an inverter that does not specify a OCPD size. >> >> Jay >> Peltz power. >> >> Sent from my iPhone >> >> On Jun 26, 2014, at 3:20 PM, Dave Click <davecl...@fsec.ucf.edu> wrote: >>> >>> Corey, >>> >>> The line of reasoning is faulty. It's 705.12(D)(1). Micro-inverters are >>> the >>> >> exception because they are specially listed to share a breaker. As for >> the other >> inverters, doubling them up on a single breaker / disconnect probably goes >> against their installation instructions [110.3(B)] and it's unlikely that >> you >> could put multiple units on a single breaker anyway because when you take >> (2 >> inverters) x (rated current) x (1.25) you will probably come up with a >> minimum >> breaker size that is larger than the maximum allowed under the NRTL >> listing to >> UL 1741. >> >>> >>> Dave >>> >>> >>> >>> On 2014/6/26, 16:18, Corey Shalanski wrote: >>>> We considered the necessity to shut down individual inverters and >>>> determined >>>> >>> that the added costs of an inverter output combiner panel were not >> merited. I >> agree that in theory it seems beneficial to be able to switch each >> inverter >> individually, but how often does this occur in practice? For the >> relatively >> infrequent cases where we need to return to a jobsite and shut down an >> inverter >> - for troubleshooting/removal/etc. - we do not mind shutting down the >> other >> inverters (up to a limit) for what is hopefully a short period of time. >> >>> >>>> Again, this whole line of reasoning may be shown to be faulty if >>>> someone can >>>> >>> directly point to the Code section that requires OCPD on each individual >> inverter. >> >>> >>>> -- >>>> Corey >>>> $E1eB >>>> >>>> >>>> On Thu, Jun 26, 2014 at 9:20 AM, <re-wrenches-requ...@lists.re- >>>>> wrenches.org> >>>>> >>>> wrote: >> >>> >>>>> Message: 5 >>>>> Date: Wed, 25 Jun 2014 19:17:57 -0700 >>>>> From: William Miller <will...@millersolar.com> >>>>> To: RE-wrenches <re-wrenches@lists.re-wrenches.org> >>>>> Subject: Re: [RE-wrenches] Combining Multiple Inverters >>>>> Message-ID: <04f4b8fd-e280-4bf2-b5a4-c2fca8d1c...@millersolar.com> >>>>> Content-Type: text/plain; charset="utf-8" >>>>> >>>>> Not allowed. You need a dedicated OCPD. Plus seems like a really bad >>>>> idea. >>>>> >>>> How do you shut down just one inverter? >> >>> >>>>> >>>>> >>>>> Miller Solar >>>>> >>>> --- end of quote --- >> _______________________________________________ >> 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 >> >> >> _______________________________________________ > 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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