Agreed: http://solarprofessional.com/article/?file=SP2_3_pg16_QandA_2&search=
You¹ll notice that none of the more permissive proposals that John mentions here actually made it into NEC 2011. On 3/30/11 1:07 PM, "Jason Szumlanski" <ja...@fafcosolar.com> wrote: > Here is a 690.64(B)(2) opinion from Wiles that may help. > http://www.fafcosolar.com/download/409/690%2064%28B%29%282%29TECH-1.pdf > > It¹s still my contention that the conductors need to be sized for 150A in this > example, unless an exception is made by the AHJ. If David Brearley¹s post > about Wiles¹ clarification is accurate, them the 80A main breaker in the > subpanel can be used for calculations, but the conductor still needs to be > sized for 80A + 80A =160A / 1.2 = 133.3A. > > > Jason > > > From: re-wrenches-boun...@lists.re-wrenches.org > [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Kent Osterberg > Sent: Wednesday, March 30, 2011 12:57 PM > To: RE-wrenches > Subject: Re: [RE-wrenches] sizing a sub-panel used to combine multiple > inverter outputs > > Al, > > How about a 15-amp single-pole breaker for power line carrier communications > equipment to talk to the inverters? > Technically, I think either way they are loads and that changes everything. > But in my opinion they are minor and should be allowed without considering the > sum of all sources. > > Kent Osterberg > Blue Mountain Solar > > > Al Frishman wrote: > Is a monitoring system installed in the Load Center to measure the cumulative > kWh¹s of the inverter¹s considered a load? > The type of monitoring device I am talking about has CT¹s that go around the > conductors and the Voltage ref is taken by attaching conductors to each phase, > the Neutral and the ground bar. The digital Meter has a 3-pole 5A breaker > in it so the conductors in the load center can be connected to lugs on the bus > bar directly. > > > Al Frishman > AeonSolar > (917) 699-6641 - cell > (888) 460-2867 > www.aeonsolar.com <http://www.aeonsolar.com/> > > > > From: re-wrenches-boun...@lists.re-wrenches.org > [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Jason > Szumlanski > Sent: Wednesday, March 30, 2011 8:18 AM > To: RE-wrenches > Subject: Re: [RE-wrenches] sizing a sub-panel used to combinemultipleinverter > outputs > > Another key is to remember that this discussion also applies to the conductor > between the main panel and subpanel. In a large PV system, this could result > in a pretty large wire between the two panels, and a significant cost that is > often overlooked. In some cases it makes sense to locate the subpanel close to > the main panel and run multiple sets of smaller wires from the inverters to > the subpanel. > > And because the calculation is based on the first OC protection connected to > the inverters, adding a main breaker (theoretically 80A in this example) in > the subpanel doesn¹t change things. Even though this wire would be > theoretically protected by an 80A breaker at each end, you can¹t size the wire > for 160A / 1.2 = 133.3A. You have to size for 180A/1.2 = 150A. (not that it > makes much of a difference in this example, but it still must be considered) > > At least that¹s how I understand it > > > Jason Szumlanski > Fafco Solar > > > > From: re-wrenches-boun...@lists.re-wrenches.org > [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Mark Frye > Sent: Wednesday, March 30, 2011 1:33 AM > To: 'RE-wrenches' > Subject: Re: [RE-wrenches] sizing a sub-panel used to combinemultipleinverter > outputs > > Opps! > > My bad, I was thinking of a single phase system, not the three phase system > shown in the article. > > For the three phase system Kent is correct in counting 180A of supply per bar. > > Mark Frye > Berkeley Solar Electric Systems > 303 Redbud Way > Nevada City, CA 95959 > (530) 401-8024 > www.berkeleysolar.com <http://www.berkeleysolar.com/> > > > > > > From: re-wrenches-boun...@lists.re-wrenches.org > [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Mark Frye > Sent: Tuesday, March 29, 2011 10:17 PM > To: 'RE-wrenches' > Subject: Re: [RE-wrenches] sizing a sub-panel used to combine multipleinverter > outputs > I think Kent and I agree. For the case where the subpanel is not dedicated a > PV sub-panel he is calculating for 2 - 50A breakers and I calculated for 3 - > 50A breakers. > > Mark Frye > Berkeley Solar Electric Systems > 303 Redbud Way > Nevada City, CA 95959 > (530) 401-8024 > www.berkeleysolar.com <http://www.berkeleysolar.com/> > > > > > > From: re-wrenches-boun...@lists.re-wrenches.org > [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Kent Osterberg > Sent: Tuesday, March 29, 2011 9:26 PM > To: RE-wrenches > Subject: Re: [RE-wrenches] sizing a sub-panel used to combine multiple > inverter outputs > Per 705.12(D) the sub-panel could be any distribution equipment on the > premises. So the question becomes: is the sub-panel capable of supplying > branch circuits or feeder loads? If yes, then the sum of the breakers > (potentially) feeding the bus is 180 amps so a 150-amp rating is required and > the inverters would have to feed the opposite end of the bus bars. If no, the > code is not clear on the requirement, but obviously the 80-amp breaker in the > main panel limits the maximum current flowing through the sub-panel. > > Kent Osterberg > Blue Mountain Solar > > > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Options & settings: > http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org > > List-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org > > List rules & etiquette: > www.re-wrenches.org/etiquette.htm > > Check out participant bios: > www.members.re-wrenches.org > > > David Brearley, Senior Technical Editor > SolarPro magazine > NABCEP Certified PV Installer > david.brear...@solarprofessional.com > Direct: 541.261.6545 > Fax: 541.512.0343 > > Visit our Web site at solarprofessional.com > > (Sample copy available for download at: solarprofessional.com/sample) > >
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