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 doesn't change things. Even though this wire would be theoretically protected by an 80A breaker at each end, you can't 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 that's 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
Re: [RE-wrenches] sizing a sub-panel used tocombinemultipleinverter outputs
Jason, I think, going back to the diagram in the article, the feeder breaker is rated at 80A, the feeder conductors are rated at 80A, and the subpanel is rated at 80A, assuming that there are no loads connected in the subpanel. Even if there were up to 100A of loads in the subpanel, you would not exceed the allowance for the feeder or the sub-panel. Still, if you do have loads in the subpanel, you have to up sizes the sub-panel, but not the feeder conductor. Mark Frye Berkeley Solar Electric Systems 303 Redbud Way Nevada City, CA 95959 (530) 401-8024 http://www.berkeleysolar.com/ www.berkeleysolar.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 5:18 AM To: RE-wrenches Subject: Re: [RE-wrenches] sizing a sub-panel used tocombinemultipleinverter 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 doesn't change things. Even though this wire would be theoretically protected by an 80A breaker at each end, you can't 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 that's 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 http://www.berkeleysolar.com/ 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 http://www.berkeleysolar.com/ 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
Re: [RE-wrenches] sizing a sub-panel used to combine multiple inverter outputs
Is a monitoring system installed in the Load Center to measure the cumulative kWh's of the inverter's considered a load? The type of monitoring device I am talking about has CT's 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 doesn't change things. Even though this wire would be theoretically protected by an 80A breaker at each end, you can't 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 that's 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 http://www.berkeleysolar.com/ 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 http://www.berkeleysolar.com/ 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
Re: [RE-wrenches] sizing a sub-panel used tocombinemultipleinverteroutputs
Hmmm. That's not the way I understood it. I could be wrong. 690(B)(2): The sum of the ampere ratings of overcurrent devices in circuits supplying power to a busbar or conductor shall not exceed 120 percent of the rating of the busbar or conductor. In systems with panelboards connected in series, the rating of the first overcurrent device directly connected to the output of a utility-interactive inverter(s) shall be used in the calculations for all busbars and conductors. The way I read it, both the inverters and the feeder circuit are supplying power to the conductor between the main and subpanels. The sum of the OC protection is 100A + 80A = 180A per leg. Therefore, the conductor must be rated for 180A / 1.2 = 150A. Maybe this changes if there are no loads in the subpanel, but I don't think so. In many cases we have a circuit for an energy monitoring device in the subpanel, so we almost always have loads anyway. Another way to read it would be that ONLY the inverter circuits shall be used for calculations, in which case the conductors would need to be 100A / 1.2 = 83.3A. However, I don't think that is the intent. While on the subject, I always wondered about that Lennox Solar A/C system that uses Enphase backfed through the A/C compressor circuit. It seemed like the conductor would need to be upgraded. Jason 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 11:36 AM To: 'RE-wrenches' Subject: Re: [RE-wrenches] sizing a sub-panel used tocombinemultipleinverteroutputs Jason, I think, going back to the diagram in the article, the feeder breaker is rated at 80A, the feeder conductors are rated at 80A, and the subpanel is rated at 80A, assuming that there are no loads connected in the subpanel. Even if there were up to 100A of loads in the subpanel, you would not exceed the allowance for the feeder or the sub-panel. Still, if you do have loads in the subpanel, you have to up sizes the sub-panel, but not the feeder conductor. 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 Jason Szumlanski Sent: Wednesday, March 30, 2011 5:18 AM To: RE-wrenches Subject: Re: [RE-wrenches] sizing a sub-panel used tocombinemultipleinverter 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 doesn't change things. Even though this wire would be theoretically protected by an 80A breaker at each end, you can't 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 that's 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: [RE-wrenches] sizing a sub-panel used tocombinemultipleinverter outputs
To echo the wording in Kent's response, John Wiles has always advised that it doesn't matter if there are currently loads connected to the panel/conductors; if the panel/conductors are capable of having additional loads connected to it, you need to apply 609.64(B)(2). I have had luck with AHJ approval by adding signage indicating that no loads can be added to this panel/fpr combining PV inverter output only, and in one case installed a panelboard dead-front that limited the number of breakers to six (for our six combining inverters). If you are installing breaker for a meter, it sounds like the panel is capable of having additional loads connected to it. For discussion on code specific combiner panel requirements, or the lack thereof, I'll quote from this list last year (response is from Bill Brooks): ** Sent: Tuesday, January 12, 2010 10:57 AM To: RE-wrenches Subject: [RE-wrenches] Solar accumulation panel *** Team wrenches - I feel like I've seen a provision in the Code for installing a sub-panel to aggregate PV inverter outputs for the purpose of simplifying the actual grid connection (such as for a line-side tap) but I can't find it in 690. I also seem to remember specific verbiage that needs to be on the panel along the lines of PV circuits only. Do not add load breakers. to ensure compliance with 690.64(B). Does anyone know where I can find this info in the NEC? Andrew Truitt Standard Solar Inc. Response: It does not exist. We tried like crazy to get it into the 2011 NEC, but to no avail. At the last second the proposal was put on hold until the 2014 NEC. Major bummer. For now it can only be done with AHJ approval. Many allow it but it is not in the NEC. Alternatively you must use the sum of supply breakers no greater than 120%. Much more restrictive. Bill. -Phil On Wed, Mar 30, 2011 at 8:36 AM, Mark Frye ma...@berkeleysolar.com wrote: Jason, I think, going back to the diagram in the article, the feeder breaker is rated at 80A, the feeder conductors are rated at 80A, and the subpanel is rated at 80A, assuming that there are no loads connected in the subpanel. Even if there were up to 100A of loads in the subpanel, you would not exceed the allowance for the feeder or the sub-panel. Still, if you do have loads in the subpanel, you have to up sizes the sub-panel, but not the feeder conductor. 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 *Jason Szumlanski *Sent:* Wednesday, March 30, 2011 5:18 AM *To:* RE-wrenches *Subject:* Re: [RE-wrenches] sizing a sub-panel used tocombinemultipleinverter 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 doesn’t change things. Even though this wire would be theoretically protected by an 80A breaker at each end, you can’t 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 that’s 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 -- *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
Re: [RE-wrenches] sizing a sub-panel used to combinemultipleinverter outputs
Jason, Now you are opening up a can of worms. It's bad enough that 705.12(D) doesn't say anything about a panel that can't (or shouldn't, or won't) have anything connected but interactive inverters. But when that is the case, a bus rating of 100% of the source circuits should apply. For PV systems a 125% factor will already apply to each inverter circuit. While it seems logical that the conductors are an extension of the bus bar and should be treated the same way, 705.12(D) isn't about the conductors - it's about the bus bars. The conductors are protected by the breakers -- 80-amp breakers and wire with 80-amp ampacity. Getting into the example further, I see flaws in it. If the inverters are 7500-watt 240-volt, the output current would be 7500/240 = 31.25 amps and 40-amp breakers would be adequate. Then there would have been no issues, even going directly into the main panel. If the inverters are 7500-watt 208-volt, the output current is 7500/208 = 36 amps and the 50-amp breakers make sense. That means the bus bars and feeder conductor have a continuous current of 72 amps. That means neither the 80-amp breaker nor 80-amp wire is sufficient because 72 x 1.25 = 90 amps. Now the example doesn't resolve the limitation of backfeeding at the main. Opps! Kent Osterberg Blue Mountain Solar Jason Szumlanski wrote: 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 doesnt change things. Even though this wire would be theoretically protected by an 80A breaker at each end, you cant 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 thats 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, Iwas thinking of a singlephase 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 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 thesubpanel 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 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 ___ List sponsored by Home Power magazine List Address: RE-wrenches@lists.re-wrenches.org Options settings:
Re: [RE-wrenches] sizing a sub-panel used to combine multipleinverter outputs
Al, I would say that yes the meter is a load and this goes to show the relative inadequacy of the vocabulary we are using in the discussion. In the example we have been using with the 80A breaker, wire and sub panel, you could have up to 80A of loads installed in the sub and still not create an over current condition in any of that equipment. Mark Frye Berkeley Solar Electric Systems 303 Redbud Way Nevada City, CA 95959 (530) 401-8024 http://www.berkeleysolar.com/ www.berkeleysolar.com _ From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Al Frishman Sent: Wednesday, March 30, 2011 9:00 AM To: 'RE-wrenches' Subject: Re: [RE-wrenches] sizing a sub-panel used to combine multipleinverter outputs Is a monitoring system installed in the Load Center to measure the cumulative kWh's of the inverter's considered a load? The type of monitoring device I am talking about has CT's 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 doesn't change things. Even though this wire would be theoretically protected by an 80A breaker at each end, you can't 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 that's 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 http://www.berkeleysolar.com/ 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 http://www.berkeleysolar.com/ 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:
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 kWhs of the inverters considered a load? The type of monitoring device I am talking about has CTs 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 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 doesnt change things. Even though this wire would be theoretically protected by an 80A breaker at each end, you cant 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 thats 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, Iwas thinking of a singlephase 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 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 thesubpanel 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 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 ___ 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:
Re: [RE-wrenches] sizing a sub-panel used to combine multiple inverter outputs
This is diagram is based on a 3-phase 208 V service, as clarified in the text accompanying the diagrams. There is a mistake of sorts, however. The authors¹ original manuscript called out a ³generic² 7500W inverter connected to 50A, 2-P breaker. We then added more detail, calling out a Fronius 7500W IG Plus inverter. However, according to the most recent product data from the manufacturer, the max AC OCPD rating for this inverter is 45A, not 50A. The example still works w/ 45A breakers: 400A + 90A = 490A, which is larger than the 480A allowed under the 120% rule. Apply the subpanel that problem is eliminated. RE: the question about which breaker to count. Code experts like Bill Brooks John Wiles have clarified that when a dedicated inverter aggregation panel is used, the breaker on the output of the panel can be considered ³the output of the utility interactive inverter(s).² The intent of the language in 690.64(B)(2) in NEC 2008 about series connected panels is not to make you count all of the breakers in a dedicated inverter aggregation panel. Rather it is to clarify that it is unnecessary use the progressively larger upstream breakers ratings, which can be ³fed² by the inverters, in your point of connection calculations. RE: the original question. I think the most correct answer is ³It depends.² It depends on your jurisdiction and your PE. A literal interpretation of the Code would appear to have you upsize the inverter aggregation panel and the feeder conductor. But there is certainly precedent for AHJs not requiring this. If you propose labeling the inverter aggregation panel ³PV Only Do Not Add Loads² and mark the feeder conductor with warnings ³PV Only Do Not Tap² wherever it is exposed, you may find that the AHJ will not require you to upsize these. Hope that¹s cleared than mud, David Brearley, Senior Technical Editor SolarPro magazine NABCEP Certified PV Installer david.brear...@solarprofessional.com Direct: 541.261.6545 On 3/30/11 11:12 AM, Kent Osterberg k...@coveoregon.com wrote: Jason, Now you are opening up a can of worms. It's bad enough that 705.12(D) doesn't say anything about a panel that can't (or shouldn't, or won't) have anything connected but interactive inverters. But when that is the case, a bus rating of 100% of the source circuits should apply. For PV systems a 125% factor will already apply to each inverter circuit. While it seems logical that the conductors are an extension of the bus bar and should be treated the same way, 705.12(D) isn't about the conductors - it's about the bus bars. The conductors are protected by the breakers -- 80-amp breakers and wire with 80-amp ampacity. Getting into the example further, I see flaws in it. If the inverters are 7500-watt 240-volt, the output current would be 7500/240 = 31.25 amps and 40-amp breakers would be adequate. Then there would have been no issues, even going directly into the main panel. If the inverters are 7500-watt 208-volt, the output current is 7500/208 = 36 amps and the 50-amp breakers make sense. That means the bus bars and feeder conductor have a continuous current of 72 amps. That means neither the 80-amp breaker nor 80-amp wire is sufficient because 72 x 1.25 = 90 amps. Now the example doesn't resolve the limitation of backfeeding at the main. Opps! Kent Osterberg Blue Mountain Solar Jason Szumlanski wrote: 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
[RE-wrenches] NABCEP Stamp
I am wondering if anyone has had a NABCEP stamp made to stamp plans. I have a city agency who is comfortable with the NABCEP certification as a qualification, but would like to see a stamp. Has anyone out there done this? Troy ___ 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
Re: [RE-wrenches] sizing a sub-panel used to combine multipleinverter outputs
Wouldn't a fault in that conductor between the main and the sub have a potential for up to 160A of current? I would think that at noon on a sunny day, the inverter system could produce 80A from one direction (albeit really only the max amperage outputs of the inverters) and 80A of grid current from the main into a partial fault. Brian Teitelbaum AEE 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 9:49 AM To: 'RE-wrenches' Subject: Re: [RE-wrenches] sizing a sub-panel used to combine multipleinverter outputs Al, I would say that yes the meter is a load and this goes to show the relative inadequacy of the vocabulary we are using in the discussion. In the example we have been using with the 80A breaker, wire and sub panel, you could have up to 80A of loads installed in the sub and still not create an over current condition in any of that equipment. Mark Frye Berkeley Solar Electric Systems 303 Redbud Way Nevada City, CA 95959 (530) 401-8024 www.berkeleysolar.comhttp://www.berkeleysolar.com/ From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Al Frishman Sent: Wednesday, March 30, 2011 9:00 AM To: 'RE-wrenches' Subject: Re: [RE-wrenches] sizing a sub-panel used to combine multipleinverter outputs Is a monitoring system installed in the Load Center to measure the cumulative kWh's of the inverter's considered a load? The type of monitoring device I am talking about has CT's 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.comhttp://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 doesn't change things. Even though this wire would be theoretically protected by an 80A breaker at each end, you can't 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 that's 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.comhttp://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.comhttp://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
Re: [RE-wrenches] sizing a sub-panel used to combinemultipleinverter outputs
I concur with Jason and Brian's interpretation of 690.64(B)(2). I think one of the intents of the code is to ensure that if there is a fault in a busbar or conductor and the maximum amperage is being delivered to that fault from all OCPDs supplying it (solar + utility), the busbar or conductor should be able to handle the sum of those fault currents. I have encountered numerous jurisdictions that interpret it this way, and it is hard to argue with them from a strictly code perspective. However, Jason Fisher once pointed out to me that if the fault occurs in a feeder between the main service panel and a subpanel (solar accumulation panel or otherwise) it is impossible for any part of that conductor to carry more current than allowed by the largest OCPD feeding the conductor. Its the same principle behind the 690.64(B)(7) requirement to locate the solar interconnection breaker at the opposite end of the busbar from the incoming feeders. This argument obviously doesn't apply to accumulation panel busbars where you have more than 2 OCPDs supplying current, but I think it is a valid argument for basing your feeder conductor sizing on the largest OCPD protecting that conductor. For a brighter energy future, Andrew Truitt Principal Truitt Renewable Energy Consulting NABCEP Certified PV Installer™ (ID# 032407-66) (202) 486-7507 http://www.linkedin.com/pub/andrew-truitt/8/622/713 [image: 24 copy.jpg] Don't get me wrong: I love nuclear energy! It's just that I prefer fusion to fission. And it just so happens that there's an enormous fusion reactor safely banked a few million miles from us. It delivers more than we could ever use in just about 8 minutes. And it's wireless! ~William McDonough On Wed, Mar 30, 2011 at 10:12 AM, Kent Osterberg k...@coveoregon.comwrote: Jason, Now you are opening up a can of worms. It's bad enough that 705.12(D) doesn't say anything about a panel that can't (or shouldn't, or won't) have anything connected but interactive inverters. But when that is the case, a bus rating of 100% of the source circuits should apply. For PV systems a 125% factor will already apply to each inverter circuit. While it seems logical that the conductors are an extension of the bus bar and should be treated the same way, 705.12(D) isn't about the conductors - it's about the bus bars. The conductors are protected by the breakers -- 80-amp breakers and wire with 80-amp ampacity. Getting into the example further, I see flaws in it. If the inverters are 7500-watt 240-volt, the output current would be 7500/240 = 31.25 amps and 40-amp breakers would be adequate. Then there would have been no issues, even going directly into the main panel. If the inverters are 7500-watt 208-volt, the output current is 7500/208 = 36 amps and the 50-amp breakers make sense. That means the bus bars and feeder conductor have a continuous current of 72 amps. That means neither the 80-amp breaker nor 80-amp wire is sufficient because 72 x 1.25 = 90 amps. Now the example doesn't resolve the limitation of backfeeding at the main. Opps! Kent Osterberg Blue Mountain Solar Jason Szumlanski wrote: 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 doesn’t change things. Even though this wire would be theoretically protected by an 80A breaker at each end, you can’t 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 that’s how I understand it… Jason Szumlanski Fafco Solar *From:* re-wrenches-boun...@lists.re-wrenches.org [ mailto:re-wrenches-boun...@lists.re-wrenches.orgre-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 -- *From:* re-wrenches-boun...@lists.re-wrenches.org [ mailto:re-wrenches-boun...@lists.re-wrenches.orgre-wrenches-boun...@lists.re-wrenches.org] *On Behalf Of *Mark Frye *Sent:* Tuesday,
Re: [RE-wrenches] sizing a sub-panel used to combine multiple inverter outputs
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 It's 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 Brearley's post about Wiles' 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 kWh's of the inverter's considered a load? The type of monitoring device I am talking about has CT's 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 doesn't change things. Even though this wire would be theoretically protected by an 80A breaker at each end, you can't 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 that's 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
Re: [RE-wrenches] NABCEP Stamp
Troy - I have not encountered this before but would you mind sharing what city agency you are refering to? NABCEP is always interested in hearing about these types of unconventional uses of the certification. For a brighter energy future, Andrew Truitt Principal Truitt Renewable Energy Consulting NABCEP Certified PV Installer™ (ID# 032407-66) (202) 486-7507 http://www.linkedin.com/pub/andrew-truitt/8/622/713 [image: 24 copy.jpg] Don't get me wrong: I love nuclear energy! It's just that I prefer fusion to fission. And it just so happens that there's an enormous fusion reactor safely banked a few million miles from us. It delivers more than we could ever use in just about 8 minutes. And it's wireless! ~William McDonough On Wed, Mar 30, 2011 at 11:04 AM, Troy Harvey tahar...@heliocentric.orgwrote: I am wondering if anyone has had a NABCEP stamp made to stamp plans. I have a city agency who is comfortable with the NABCEP certification as a qualification, but would like to see a stamp. Has anyone out there done this? Troy ___ 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 24 copy.jpg___ 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
Re: [RE-wrenches] sizing a sub-panel used to combine multiple inverter outputs
Agreed: http://solarprofessional.com/article/?file=SP2_3_pg16_QandA_2search= 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
Re: [RE-wrenches] sizing a sub-panel used to combinemultiple inverter outputs
By this argument, wouldn't it be necessary to check every conductor in the backfeed path adding potential PV amps to their required ampacity including the utility conductor from the transformer? Kris Legacy Solar, LLC 864 Clam Falls Trail Frederic, WI 54837 715-653-4295 sol...@legacysolar.com www.legacysolar.com -Original Message- 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 1:08 PM To: RE-wrenches Subject: Re: [RE-wrenches] sizing a sub-panel used to combinemultiple inverter outputs 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 It's 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 Brearley's post about Wiles' 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 kWh's of the inverter's considered a load? The type of monitoring device I am talking about has CT's 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 doesn't change things. Even though this wire would be theoretically protected by an 80A breaker at each end, you can't 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 that's 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 http://www.berkeleysolar.com/ 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 http://www.berkeleysolar.com/ 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
Re: [RE-wrenches] sizing a sub-panel used tocombinemultiple inverter outputs
I hope there are no potential loads between the meter and the transformer, so no! Technically, if it is a supply side tap, the evaluation would include the conductor from the meter to the main distribution panel I believe, but if it is a load side connection it does not matter because of the main breaker in the main distribution panel. Honestly, I've never closely scrutinized the meter-MDP wiring for supply side connections, but I am confident that a limitation never came into play. Jason From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Kristopher Schmid Sent: Wednesday, March 30, 2011 2:28 PM To: 'RE-wrenches' Subject: Re: [RE-wrenches] sizing a sub-panel used tocombinemultiple inverter outputs By this argument, wouldn't it be necessary to check every conductor in the backfeed path adding potential PV amps to their required ampacity including the utility conductor from the transformer? Kris Legacy Solar, LLC 864 Clam Falls Trail Frederic, WI 54837 715-653-4295 sol...@legacysolar.com www.legacysolar.com -Original Message- 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 1:08 PM To: RE-wrenches Subject: Re: [RE-wrenches] sizing a sub-panel used to combinemultiple inverter outputs 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 It's 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 Brearley's post about Wiles' 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 kWh's of the inverter's considered a load? The type of monitoring device I am talking about has CT's 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 (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 doesn't change things. Even though this wire would be theoretically protected by an 80A breaker at each end, you can't 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 that's 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
Re: [RE-wrenches] sizing a sub-panel used tocombine multipleinverter outputs
Per your question:
1 - What does a UL1741 inverter do when it is connected
to a
line that is experiencing a short-circuit or ground fault?
Presuming a hard short, the voltage in that circuit would be essentially zero,
and a UL1741 compliant inverter would cease producing power in less than 0.1
second.
Dan
Sr. Engineer
Exeltech
--- On Wed, 3/30/11, Mark Frye ma...@berkeleysolar.com wrote:
From: Mark Frye ma...@berkeleysolar.com
Subject: Re: [RE-wrenches] sizing a sub-panel used tocombine multipleinverter
outputs
To: 'RE-wrenches' re-wrenches@lists.re-wrenches.org
Date: Wednesday, March 30, 2011, 12:37 PM
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That is a really good question Brian.
Mostly when thinking about these sizing issues I think about
overload conditions and not so much about short-circuit and ground fault
conditions.
So two questions come up:
1 - What does a UL1741 inverter do when it is connected to a
line that is experiencing a short-circuit or ground fault?
2 - What does the feeder breaker do when it is connected to a
line that is experiencing a short-circuit or ground fault?
As far as number two, thanks to all the great work we do
establishing low impedence fault paths back to circuirt protectors, the breaker
is going to trip at it's rating and protect the wire at the same
rating. But that doesn't mean that the conductor won't see more
than rated amps during the fault. It will see alot more than for a
very short time. During this very short time frame, the actual currents flowing
into the fault from the utility side of the equation far far exceed the
currents
contributed by the power limited inverter side.
Mark Frye
Berkeley Solar Electric
Systems
303 Redbud
Way
Nevada
City, CA 95959
(530) 401-8024
www.berkeleysolar.com
From: re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Brian
Teitelbaum
Sent: Wednesday, March 30, 2011 10:02 AM
To:
RE-wrenches
Subject: Re: [RE-wrenches] sizing a sub-panel used
tocombine multipleinverter outputs
Wouldn’t
a fault in that conductor between the main and the sub have a potential for up
to 160A of current? I would think that at noon on a sunny day, the inverter
system could produce 80A from one direction (albeit really only the max
amperage
outputs of the inverters) and 80A of grid current from the main into a partial
fault.
Brian
Teitelbaum
AEE
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 9:49 AM
To:
'RE-wrenches'
Subject: Re: [RE-wrenches] sizing a sub-panel used to
combine multipleinverter outputs
Al,
I would
say that yes the meter is a load and this goes to show the relative inadequacy
of the vocabulary we are using in the discussion. In the example we have been
using with the 80A breaker, wire and sub panel, you could have up to 80A of
loads installed in the sub and still not create an over current condition in
any
of that equipment.
Mark
Frye
Berkeley
Solar Electric Systems
303
Redbud Way
Nevada
City, CA 95959
(530)
401-8024
www.berkeleysolar.com
From:
re-wrenches-boun...@lists.re-wrenches.org
[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Al
Frishman
Sent: Wednesday, March 30, 2011 9:00 AM
To:
'RE-wrenches'
Subject: Re: [RE-wrenches] sizing a sub-panel used to
combine multipleinverter outputs
Is
a monitoring system installed in the Load Center to measure the cumulative
kWh’s
of the inverter’s considered a load?
The
type of monitoring device I am talking about has CT’s 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
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
Re: [RE-wrenches] sizing a sub-panel used tocombinemultipleinverter outputs
Right, so going totally on the fly at the white board, let's say we have an inverter with a 45A AC output, it see's the short and pours it's little heart out at 45A for 0.1 sec before shutting out, delivering 4.5 A-sec of energy into the fault. Meanwhile we take out a clearing time curve for the generic 60A breaker that the inverter would be backfeed at the other end of the feeder. It will deliver 10 times it's rating or 600A for 0.5 secs before clearing. That's 300 A-sec of energy, 66 times more than the inverter. So can we say that when looking at sizing the AC side of these inverters we need more to concern ourselves with continuous overload conditions and not so much with short-circuit/ground fault conditions? Mark Frye Berkeley Solar Electric Systems 303 Redbud Way Nevada City, CA 95959 (530) 401-8024 http://www.berkeleysolar.com/ www.berkeleysolar.com _ From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Exeltech Sent: Wednesday, March 30, 2011 12:04 PM To: RE-wrenches Subject: Re: [RE-wrenches] sizing a sub-panel used tocombinemultipleinverter outputs Per your question: 1 - What does a UL1741 inverter do when it is connected to a line that is experiencing a short-circuit or ground fault? Presuming a hard short, the voltage in that circuit would be essentially zero, and a UL1741 compliant inverter would cease producing power in less than 0.1 second. Dan Sr. Engineer Exeltech --- On Wed, 3/30/11, Mark Frye ma...@berkeleysolar.com wrote: From: Mark Frye ma...@berkeleysolar.com Subject: Re: [RE-wrenches] sizing a sub-panel used tocombine multipleinverter outputs To: 'RE-wrenches' re-wrenches@lists.re-wrenches.org Date: Wednesday, March 30, 2011, 12:37 PM That is a really good question Brian. Mostly when thinking about these sizing issues I think about overload conditions and not so much about short-circuit and ground fault conditions. So two questions come up: 1 - What does a UL1741 inverter do when it is connected to a line that is experiencing a short-circuit or ground fault? 2 - What does the feeder breaker do when it is connected to a line that is experiencing a short-circuit or ground fault? As far as number two, thanks to all the great work we do establishing low impedence fault paths back to circuirt protectors, the breaker is going to trip at it's rating and protect the wire at the same rating. But that doesn't mean that the conductor won't see more than rated amps during the fault. It will see alot more than for a very short time. During this very short time frame, the actual currents flowing into the fault from the utility side of the equation far far exceed the currents contributed by the power limited inverter side. Mark Frye Berkeley Solar Electric Systems 303 Redbud Way Nevada City, CA 95959 (530) 401-8024 http://www.berkeleysolar.com/ www.berkeleysolar.com _ From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Brian Teitelbaum Sent: Wednesday, March 30, 2011 10:02 AM To: RE-wrenches Subject: Re: [RE-wrenches] sizing a sub-panel used tocombine multipleinverter outputs Wouldn't a fault in that conductor between the main and the sub have a potential for up to 160A of current? I would think that at noon on a sunny day, the inverter system could produce 80A from one direction (albeit really only the max amperage outputs of the inverters) and 80A of grid current from the main into a partial fault. Brian Teitelbaum AEE 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 9:49 AM To: 'RE-wrenches' Subject: Re: [RE-wrenches] sizing a sub-panel used to combine multipleinverter outputs Al, I would say that yes the meter is a load and this goes to show the relative inadequacy of the vocabulary we are using in the discussion. In the example we have been using with the 80A breaker, wire and sub panel, you could have up to 80A of loads installed in the sub and still not create an over current condition in any of that equipment. Mark Frye Berkeley Solar Electric Systems 303 Redbud Way Nevada City, CA 95959 (530) 401-8024 http://www.berkeleysolar.com/ www.berkeleysolar.com _ From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Al Frishman Sent: Wednesday, March 30, 2011 9:00 AM To: 'RE-wrenches' Subject: Re: [RE-wrenches] sizing a sub-panel used to combine multipleinverter outputs Is a monitoring system installed in the Load Center to measure the cumulative kWh's of the inverter's considered a load? The type of monitoring device I am talking about has CT's that go around the conductors and the Voltage ref is taken by attaching conductors to each phase, the Neutral and the ground bar.The
Re: [RE-wrenches] NABCEP Stamp
Troy, On Mar 30, 2011, at 10:04 AM, Troy Harvey wrote: I am wondering if anyone has had a NABCEP stamp made to stamp plans. I have a city agency who is comfortable with the NABCEP certification as a qualification, but would like to see a stamp. Has anyone out there done this? Troy I'm with Andrew here. If a NABCEP stamp of some kind makes the city happy and greases your permit approval, that's OK. If it is a city requirement, then we'd sure like to know about that. IF you do have one made, please remember to follow the NABCEP guidelines as to the use of our Mark. IE, your name -not the company name and not nothing- has to appear next to the Mark. Cheers, bob-O ___ 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
Re: [RE-wrenches] NABCEP Stamp
I hate to mention the evil insurance industry. However, a stamp implies some professional liability insurance to me. There are other professional membership organizations (RESNET) that have developed a tailored professional liability insurance package for its credentialed members with a preferred vendor. Is NABCEP looking toward this? I do not know if there is a need, but may be an advantage under certain circumstances. Peace, Erika REpower SOLUTIONS www.repowersolutions.com P: 216.268.2275 C: 216.402.4458 -Original Message- From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Bob-O Schultze Sent: Wednesday, March 30, 2011 5:47 PM To: RE-wrenches Subject: [SPAM] Re: [RE-wrenches] NABCEP Stamp Troy, On Mar 30, 2011, at 10:04 AM, Troy Harvey wrote: I am wondering if anyone has had a NABCEP stamp made to stamp plans. I have a city agency who is comfortable with the NABCEP certification as a qualification, but would like to see a stamp. Has anyone out there done this? Troy I'm with Andrew here. If a NABCEP stamp of some kind makes the city happy and greases your permit approval, that's OK. If it is a city requirement, then we'd sure like to know about that. IF you do have one made, please remember to follow the NABCEP guidelines as to the use of our Mark. IE, your name -not the company name and not nothing- has to appear next to the Mark. Cheers, bob-O ___ 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 ___ 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
Re: [RE-wrenches] Expansion joints
I recently used a Hubbell Killark product for rigid/IMC and was not happy with how the threads of the coupling engaged in factory conduit threads. Crousehinds XJG-EMT series is intended for EMT. And is described as being used indoors or outdoors. The EMT couplings mostly seem to be compression. REpower SOLUTIONS www.repowersolutions.com P: 216.268.2275 C: 216.402.4458 From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Jamie Johnson Sent: Tuesday, March 29, 2011 2:33 PM To: RE-wrenches Subject: [SPAM] Re: [RE-wrenches] Expansion joints Peter, Cooper makes one for 1.5 emt, not sure if it is rated for wet locations or not. part #XJG54 EMT, it allows for up to 4 max of conduit movement. Jamie Johnson NABCEP Certified PV Technical Sales Professional NABCEP Certified Solar PV Installer General Manager SOLAR POWER ELECTRIC Original Message Subject: [RE-wrenches] Expansion joints From: Peter Parrish peter.parr...@calsolareng.com http://peter.parr...@calsolareng.com%3e ; Date: Tue, March 29, 2011 1:04 pm To: 'RE-wrenches' re-wrenches@lists.re-wrenches.org Does anyone have information (manu and part number) for expansion joints for 1-1/2 EMT? I have also heard that many EJs are designed for rigid conduit (RMC) and may not be directly applicable to EMT. - Peter Peter T. Parrish, Ph.D., President California Solar Engineering, Inc. 820 Cynthia Ave., Los Angeles, CA 90065 CA Lic. 854779, NABCEP Cert. 031806-26 peter.parr...@calsolareng.com Ph 323-258-8883, Mobile 323-839-6108, Fax 323-258-8885 ___ 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 image001.jpg___ 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
Re: [RE-wrenches] NABCEP Stamp
Andrew and Troy, While I can't speak for NABCEP, I would expect that NABCEP should be very opposed to this type of use of their logo. NABCEP does not certify the work that a NABCEP certificant does. They only certify that the installer has met the obligations for certification. There is a HUGE difference between the two. NABCEP cannot, and should not, be held accountable for work that someone does in the field. A contactor's work is covered by the state laws and the licenses required to perform that work in that state. Just because a local jurisdictions thinks that getting a certification from NABCEP means something to the installation, does not mean that the information should be on the plan set. Information about the certification of the installer should be provided separately. Don't make a stamp, whatever you do. Bill. From: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Andrew Truitt Sent: Wednesday, March 30, 2011 10:57 AM To: RE-wrenches Subject: Re: [RE-wrenches] NABCEP Stamp Troy - I have not encountered this before but would you mind sharing what city agency you are refering to? NABCEP is always interested in hearing about these types of unconventional uses of the certification. ___ 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
