Hi All, I have a follow up to this discussion. What's the proper way to think through this regarding ground mounts? It seems to me that if the goal is to protect firefighters then running a conduit underground and coming up to outdoor wall mounted inverters is keeping in the spirit of things, but I'm not sure if the language of 690.12 supports this. Am I mistaken? Do you have any best practice advice for this scenario?
Best regards, -N On Tue, Jan 21, 2014 at 12:36 PM, Drake < drake.chamber...@redwoodalliance.org> wrote: > > Bill, > > It is good to see that energized conductors are going to be disconnected > near the arrays. I've been an advocate of disconnecting these conductors by > ground fault sensing equipment since ground fault detection was first > implemented in the code. If contactors are to be installed on roofs, it > likely won't be long before both ground faults and arc faults are > automatically cleared. > > When the requirement for AC arc fault branch circuit protection was first > put in the NEC, it was postdated to allow time for the electrical industry > to adapt. This new remote disconnecting requirement does not provide any > lead time. > > As the 2014 NEC is adopted in various jurisdictions, inspectors may feel > that it is necessary to disallow systems without the newly required > disconnect feature. This may result in serious problems for solar companies > and customers, as well as manufacturers. > > The protection of firefighters is essential. The implementation of > renewables is essential also. Insurance claims for weather related, global > warming-triggered climatic disasters are rising exponentially. Extreme > weather related events result in major loss of life and billions of dollars > in property damage. Atmospheric CO2 levels continue to climb from the > burning of fossil fuels. This is a crisis of global proportions. > > My request for code writers is to please take into account the effect that > inserting new rules into the NEC may have on the stability of renewable > energy, and implement new requirements in a way that will allow for a > smooth interface. > > Thank you, > > Drake > > Drake Chamberlin > > > > > > *Athens Electric LLC OH License 44810 CO License 3773 NABCEP Certified > Solar PV 740-448-7328 <740-448-7328> *http://athens-electric.com/ > > > At 12:45 PM 1/16/2014, you wrote: > > Content-Type: multipart/alternative; > boundary="----=_NextPart_000_0F94_01CF129F.BCC65BD0" > Content-Language: en-us > > > Jeffrey, > > Sounds like you need to get involved in the code making process since you > have so many good ideas on how to improve the language. I like > confrontational discussions as long as they lead to a better understanding > and constructive outcomes. > > About 30 people worked on this language, so it is definitely not perfect. > However, I don’t think it is quite as bad as you make it out to be. I > wanted to jump in since some of your conclusions were not correct. > > This is a circuit requirement, not a disconnecting means requirement, > since it has to do with shock hazard of PV circuits in and around a > building. This is for firefighter safety. 30V is the international standard > for touch safe in a wet location. 240VA is to set a limit on the available > power on a circuit. Contactor combiners, which would be part of a compliant > solution, have 24V control circuits. The other reasoning for 240VA is that > internally, 72-Cell PV modules can be divided into segments of this power > level for the foreseeable future (more on that another day). > > If the conductors stay outside, you have 10’ from the array to place your > shutdown device. On large central systems, this would likely be a contactor > combinermost manufacturers sell these. If the conductors are going > immediately into the building, as with residential and integrated systems, > a shutdown device would have to be within 5’ of entering the building. If > goes outside for a while, then inside the building, the total length could > be no more than 10’ and no more than 5’ inside the buildingthis is not > additive. Remember, all this is for firefighter safety. > > As Brian Mehalic and others have pointed out, the language does not > specify where the shutdown initiating device is to be located. The lack of > detail is more for flexibility than it is to give an AHJ license to make an > installer do anything they want. > > With grid-tie only systems (no battery backup), it would be most > convenient and cost effective to have a system that initiates the shutdown > on loss of utility. In this way, a firefighter can do what they normally > do, shut down utility power to the building, and the rapid shutdown would > automatically initiate. This does not necessitate an additional > disconnecting means for a load-side PV connection. The main breaker could > be the initiating device. For a supply-side connection, the NEC already > requires that the PV disconnect switch be located adjacent to the service > disconnecting means (article 230). > > The biggest issue with string inverters (central inverters) is that there > is a need to shutdown the capacitor input side of the inverter since that > stays energized for 5 minutes or more. The 10 seconds was to provide a > means to rapidly discharge the capacitors rather than requiring a relay or > tripping device. Doing something other than a relay will require a test > laboratory to evaluate the functionguess what?we don’t have a standard > yet to evaluate those products. Sounds like you might want to work on that > committee. > > It is more complicated for battery backup systems. Midnite Solar’s > birdhouse products are the best I have seen so far to address this concern. > Since dc and ac circuits are not differentiated, battery backup systems > need to have a shutdown process that works independently of a utility > outage for obvious reasons, and it must shutdown both the dc circuits and > the backup ac circuits. A separate switch, like the birdhouse, would be > necessary that only controls these functions in an emergency situation. > > Is the language not detailedpossibly. This was done to provide > flexibility rather than create problems. Fire departments have been > requiring rooftop disconnects for years in California. These disconnects > are nearly worthless from a shock prevention point of view since capacitors > in the inverter stay charged or there are multiple disconnecting means > feeding each other. We have been trying to hold the fire community off of > rooftop disconnect requirements so we could work on a solution that > actually does what they want it to do. There is a long discussion on this > in the appendix of my “Understanding the CalFire Guidelines” document on > the SolarABCs website. > > The 2014 NEC language was a compromise worked out with the solar industry > (yes string inverter companies as well) in response to the first version of > the proposal which was to require module-level shutdown. This is not > module-level shutdown, it is PV output circuit shutdown (combiner box > shutdown is another way to look at it). However, the 2017 NEC cycle is this > year and there was a lot of talk about requiring module-level shutdown this > time around. > > I hope this helps. I will be writing articles for IAEI journal and other > periodicals on this subject since it was a very far-reaching and > potentially confusing new requirement in the NEC. Thanks for your interest > and let’s keep the constructive dialogue going on the subject. It is time > to get involved in the NEC update process again. > > Bill Brooks. > > *From:* re-wrenches-boun...@lists.re-wrenches.org > [mailto:re-wrenches-boun...@lists.re-wrenches.org<re-wrenches-boun...@lists.re-wrenches.org>] > *On Behalf Of *Jeffrey Quackenbush > *Sent:* Thursday, January 16, 2014 1:09 AM > *To:* RE-wrenches > *Subject:* Re: [RE-wrenches] NEC 2014 690.12 Rapid Shutdown > > Wrenches, > > There is no guidance in the Code text for where the shutdown should take > place. (1) says: "Requirements for controlled conductors shall apply only > to PV system conductors of more than 1.5m (5') in length inside a building, > or more than 3m (10') from a PV array." > > > So, the provisions *apply if* the circuit 10' from the array and 5' > inside a building, but no mention is made of where the shutdown actually > needs take place in the circuit. In the video Bill Brooks suggests that the > shutdown mechanism should also be placed within this 10'/5' boundary but > that is just an inference -- nowhere in the text is this actually > specified. If that was the intent of the Code committee, then they've done > a poor job actually expressing it in English. > > I'm concerned that some AHJs will interpret this to exclude all central > inverter systems (without the addition of cost-inducing secondary DC-DC > converters like Tigo) because the combiner or junction box can be many feet > from the actual beginning of a home run under the array. Alternately, > permissive AHJs could allow this function to be fulfilled anywhere, meaning > that the implementation won't meet the intent of the writers. > > I'm also concerned, as Isaac mentioned, that there are no requirements for > how the shutdown be initiated, or that it contains of the accessibility and > grouping requirements that are always included for disconnects. I really > think this should be treated and categorized as a disconnect requirement, > not a circuit requirement, because that is the ultimate function that's > intended. > > I'm surprised none of the inverter manufacturers have chosen to comment > here, as this could dramatically impact the sales of central inverters. > > Jeffrey Quackenbush > > > > ------------------------------ > [image: []] <http://www.avast.com/> <http://www.avast.com/> > > This email is free from viruses and malware because avast! > Antivirus<http://www.avast.com/>protection is active. > > _______________________________________________ > 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 > > > -- Nathan Charles Engineer NABCEP Certified PV Installation Professional #042013-20 Paradise Energy Solutions (717) 283-2021 direct
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