I believe this is the tenK solar product being talked about. Jay Peltz power
Sent from my iPhone On Sep 18, 2013, at 8:49 AM, August Goers <aug...@luminalt.com> wrote: > Hi Charlie, > > I can't help but be intrigued by your setup here. It seems like the complete > opposite of where our commercial systems are going with transformerless 1000 > V inverters entering the market. Anyway, I'm sure it's an interesting project > and there may very well be advantages to the system you're building. > > I agree with Dave below that you should be okay with a #6 run to a ground > rod. Otherwise, your logic for sizing the GEC seems correct. We deal with > this similar issue when designing battery backup systems and the GEC can get > unwieldy very quickly. I would just point out your sizing logic per > 250.166(C) on your plans for the inspector to see. > > Best, > > August > > From: re-wrenches-boun...@lists.re-wrenches.org > [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Dave Click > Sent: Wednesday, September 18, 2013 5:38 AM > To: re-wrenches@lists.re-wrenches.org > Subject: Re: [RE-wrenches] GEC sizing for a high amp, low voltage PV system > with microinverters > > I think Gary may be overthinking this. If the micro-inverters have a GEC lug > then you'll need to run a GEC. > > If you run your GEC to a ground rod, then you don't need to use one larger > than #6 per 250.166(C). (note also (D) and (E) but they're less useful to you > here) > > Commentary: > It makes no sense to me why the NEC can require a 0.9in diameter, #600mcm GEC > for some systems (not this one) per 250.166(B) and then say "oh wait, you > installed a single ground rod? Then a #6 is all you need!" in 250.166(C). But > it certainly makes our lives easier. > > If the building GE is not a ground rod, you could still run your #6 GEC to > that new ground rod, and then bond that rod to the existing electrode using > whatever size jumper is required per 250.53 (which I believe would also be a > #6). This lets you keep that 300' run as a #6 rather than a #4 or #2 that may > be required otherwise. > > DKC > > On 2013/9/17 23:56, Gary Willett wrote: > Charlie: > > The answer depends on whether the "system" (modules and micro-inverters) is > "grounded" or "ungrounded". I think you are describing a "grounded" system, > but it's not totally clear based on your issue description. > > If the micro-inverter is "transformer-less" the conductors are not isolated > between the DC-in and the AC-out. This requires the micro-inverter to have no > DC-side system ground. The micro-inverter AC-side always requires an EGC. > > I am assuming that the PV modules are in close proximity to the > micro-inverters, and the 300' home-run is for the AC outputs of the > micro-inverters. > > Is either DC bus (PV+ or PV-) a grounded conductor, or are both busses > ungrounded? If the DC-side combiners and re-combiners have OCPDs and > disconnecting means for both PV+ and PV-, then your system is considered to > be "floating" or "ungrounded". > > If the system is "ungrounded", a GEC is not required on the DC-side of the > micro-inverter, and only an AC-EGC sized per NEC 690.45 is required. > > If the DC-side combiners and re-combiners have OCPDs and disconnecting means > for only one conductor (PV+ or PV-), then your PV system is considered to be > "grounded". If the system is "grounded", the combined DC-GEC and AC-EGC > sizing requirements in NEC 690.47(C)(3) apply. The larger of the EGC (Table > 250.122) and GEC [250.166(B)] sizes will be required. > > More specifics on the PV module Vmpp and micro-inverter you're dealing with > would be helpful. > > Regards, > > Gary Willett > Icarus Solar > > > On 9/17/13 8:37 PM, Aladdin Solar wrote: > We will be installing a 40KW grid-tied PV system that uses PV modules wired > in parallel as per the module manufacturer -- so it's a high amperage, low > voltage system on the DC side. 2 branches of about 3KW of parallel wired > modules each come together onto a DC bus. The DC branch conductors are sized > as 2AWG. > > The inverter system provided by the manufacturer consists of a number of > UL1741 single phase microinverters that all are powered off of the low > voltage DC bus. So there's a bunch of microinverters in parallel, combined > output is single phase power. > > Those microinverters have a ground lug labeled "GEC". You know where this is > going... > > Assuming we are following NEC 690.47(C)(3), we'll be treating this ground as > GEC and following all the GEC rules. My understanding is that because the DC > conductors within the array are 2AWG (NEC 250.166(B), we will need to connect > all 12 branches and 6 DC buses with continuous 2AWG and bring it all the way > back 300' to where the AC GEC bond is located. We're getting a lot of > pushback from the electrical sub and even some disagreement from the module > manufacturer on this--no one's ever seen a grounding conductor of this size > being required for this application. > > Please don't get too bogged down with understanding the low voltage, parallel > module spec and the massive number of microinverters involved. What I'm > looking for is confirmation that I am properly understanding how the NEC GEC > requirements apply, especially to the GEC size. > > Charlie Pickard > NABCEP Certified PV Installation Professional ™ > Aladdin Solar, LLC > > > __________ Information from ESET NOD32 Antivirus, version of virus signature > database 8813 (20130917) __________ > > The message was checked by ESET NOD32 Antivirus. > > http://www.eset.com > > > > _______________________________________________ > List sponsored by Home Power magazine > > List Address: RE-wrenches@lists.re-wrenches.org > > Change email address & 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 > > Change email address & 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 > > Change email address & 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 >
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