Re: [RE-wrenches] 2014 NEC
I recently took a code update course with the electrical inspector in Andover MA, and he said that he is only allowing micro-inverter systems in his jurisdiction at the moment. SolarEdge and other auxiliary optimizers are not able to certify that they will shut down within 10 seconds. I understand that the manufacturers are working on this, but I'm not sure about their timeframe. Most jurisdictions in MA, I believe, are accepting SolarEdge or Tigo systems, but they don't comply at the moment with the 10 second shut-down provision in 690.12 (2). The inspector said that he is interpreting 690.12 (1) to say that the means of performing the shutdown should be within 10'/5' of the array, so that means locating the shutdown means on the roof in most cases. The last time I brought this up on the Wrenches list, it was suggested installers could use some kind of relay setup with an accessible activation switch and a relay disconnect. However, 690.12 (5) says: "Equipment that performs the rapid shutdown shall be listed and identified". 690.12 (5) unfortunately doesn't tell us what the equipment should be listed and identified for. It could be listed and identified for the circuit characteristics and shutdown time, or it could be listed and identified for the requirements of 690.12 as a whole function with its own UL specifications. It's possible to find equipment for the former interpretation, but I'm not aware of anything available for the latter (is anyone writing a UL regime for this?). And I think that the latter interpretation is reasonable, given the ambiguity in the way the text is written, and what is usually meant by "listed and identified" taken together. I like micro-inverters for small systems. And I like the SolarEdge model for larger systems with weird layouts, shading issues, or a premium on production. However, central inverters are, depending on the configuration and size of the system, 0.05 $/W to 0.25 $/W less expensive than micro-inverters or DC optimizer systems, and that increase in cost is most likely to come out of the contractor's pocket. I also see this affecting sales for companies producing central inverters as the 2014 code rolls out across the country. If someone has a solution for central inverters under 690.12 when dealing with skeptical AHJs, I'd appreciate hearing more about it. Regards, Jeffrey Quackenbush On Tuesday, May 20, 2014 2:07 PM, Phil Forest wrote: > > >All in all, not longer, glad to say. >Strings can have more modules, so there's fewer home runs. Optimizer wires are >longer than module wires, they even reach when installing modules in >landscape, so fewer jumpers. Be thoughtful when mounting optimizers to rails >so it's easy to connect after module is clamped down. Bolts that attach >optimizers slide into rails from the end (UniRac SM type rails). You supply >your own nuts and bolts. They supply a star washer for bonding optimizer to >rail for EG. >We mounted optimizers to modules on one job when using UniRac Sunframe. >SunFrame is a pain in my neck, optimizers or not. > >Phil Forest >South Mountain Company > >On May 20, 2014, at 1:33 PM, Will White wrote: > > >Phil, > >Do you find that the DC optimizer adds to the amount of time on an install? > >Thanks, >Will > >From: RE-wrenches [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf >Of Phil Forest >Sent: Tuesday, May 20, 2014 1:26 PM >To: RE-wrenches >Subject: Re: [RE-wrenches] 2014 NEC > >Will, >No problems with inspectors for us in MA, regarding rapid shutdown, since we >recently switched to using SolarEdge central inverters with optimizer under >each module, for roof mounted installs. >So far so good. They seem well made and engineered. Tip: you have to enable >the arc fault protection when commissioning, ships disabled. >Phil Forest >South Mountain Company > >On May 20, 2014, at 10:59 AM, Will White wrote: >Wrenches, >> >>Is anyone else having problems with inspectors and the 2014 NEC? In Mass >>we’re having all kinds of issues with inspectors requiring/allowing an array >>of different things for 690.12 rapid shut down ranging from roof top >>disconnects, disconnects on the side of a house 20’ up, disconnects in >>attics, or only disconnects that can be activated on the ground. It varies >>between inspectors. >> >>We’re also having problems with one inspector requiring arc fault breakers on >>Enphase even though there are no UL listed arc fault breakers that can be >>back fed or he wants us to run the trunk cable in a raceway. >> >>It’s getting very difficult to install in Mass. >> >>Thanks, >>Will >> >>Will White &
Re: [RE-wrenches] Temperature Compensation calcs for wire
William, I was confused by this too until I stared at it for awhile. In the bolded heading to all the tables 310.15 (16) – (20), it says either "Based on Ambient Air Temperature of 40C (104F)" or "Based on Ambient Air Temperature of 30C (86F)". Basically conductors with a temperature rating of 150C+ use the 40C de-rate factors and conductors rated 60C to 90C (which is what a PV installer will use in almost every scenario) use the 30C column. These temp de-rate values used to be posted directly under the ampacity tables, so you wouldn't have noticed the difference between the 40C and 30C values before 2011. Jeffrey Quackenbush On Friday, January 24, 2014 9:43 PM, William Miller wrote: Dave: > >Thanks for this post, although in order to completely understand, it I >sacrificed a significant amount of time working up a spreadsheet and running >various scenarios. My philosophy is that this will pay off in the long run. >I always create a spreadsheet so I can figure something out once and use it >always. > >When analyzing these codes, I was wondering which table to use: table >310.15(B)(2)(a) or table 310.15(B)(2)(b), and why? The values are >significantly different. For example at 62°C the values are 0.65 and 0.71, >respectively. I deduced that they must be used in conjunction with ampacity >values from the correct 310.15(16) through (20) tables in regards to ambient >temperature. I noted that for THWN the later tables (40°) do not go below >8AWG, so I figure I need to stick with 30° tables. Is this correct? > >Lastly, has anyone used the 310.15(C) formula for calculating the values. >This should not be that hard. What is considered "Engineering Supervision"? > >Thanks again. > >William > >-Original Message- >From: re-wrenches-boun...@lists.re-wrenches.org >[mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Dave Click >Sent: Wednesday, January 22, 2014 5:32 PM >To: re-wrenches@lists.re-wrenches.org >Subject: Re: [RE-wrenches] Temperature Compensation calcs for wire > >William- > >Yes, you can use the 90C column for ampacity adjustment when using 90C wire, >per the awkward 110.14(C)- "Conductors with temperature ratings higher than >specified for terminations shall be permitted to be used for ampacity >adjustment, correction, or both." > >Assuming copper wiring and the NEC '11 T310.15(B)(16): >Let's say you have a 40A breaker with a 75C terminal rating and you're >looking to land THWN-2 on it. Since the terminal has a 75C rating, you need >to make sure that this terminal rating is rated for at least 40A in the 75C >column. Since a 75C terminal with a #10 can only handle 35A, you'd have to >go to a #8 to get a rating of at least 40A-- in this case, a #8/75C can >handle 50A. > >So why install 90C-rated conductors at all? When using 90C conductors you >can use the 90C ampacity column to apply your derate factors. Let's say your >#8 conductor (selected above) is in 50C ambient with 4 conductors in the >raceway. > >If using #8 THWN, use 75C columns: >50A x 0.75 (T310.15(B)(2)(a)) x 0.8 = 30A That's too small for a 40A >breaker, so you're stuck with a #6: >65A x 0.75 x 0.8 = 39A (OK) > >IF using #8 THWN-2, can use 90C columns: >55A x 0.82 x 0.8 = 36A (OK per 240.4(B)) > >And I'll beat Mr. Brearley to posting a relevant SolarPro article: >http://solarprofessional.com/articles/design-installation/code-compliant-con >ductor-sizing?v=disable_pagination > >DKC > >On 2014/1/22, 19:32, William Miller wrote: >> Friends: >> >> I try to be rigorous in application of NEC codes to everything I do, >> including wire sizing. I understand that even though I am using >> conductors rated at 90°C, the breakers I use have terminals rated at >> 75°C so when deriving the values for ampacity for a given gauge from >> the tables, I have to use the 75°C column. >> >> What is not clear, however, is which column I use when applying >> temperature derating. Table 315(B)(2)(b) has a column for 75 and a >> column for 90. I am using 90° wire. The values for 90° are much more >> generous than the 75° values and I would like to use them. Which is >> correct? >> >> As always, thanks to everyone on this list for all of the help and advice. >> >> William >> >> Gradient Cap >> >> Lic 773985 >> >> millersolar.com <http://www.millersolar.com/> >> >> 805-438-5600 >> >> >> >> ___ >> List sponsored by Home Power magazine >> >> List Address: RE-wrenches@lists.re-wrenches.org >> >>
Re: [RE-wrenches] RE-wrenches Digest, Vol 7, Issue 29
Ray-- What poisonous fumes do lead-acid batteries off-gas? I know they off-gas hydrogen, which can be an explosion hazard -- but hydrogen isn't poisonous. Or were you thinking about a different type of battery. Jeffrey Quackenbush On Thursday, January 23, 2014 8:19 PM, Ray Walters wrote: I must jump on my soap box, as I have so many time in the past, and follow up Glenn's comment here. We worry so much about details of PV arrays, while batteries are serious safety hazards that no one (including the NEC) ever wants to address. Not only can they not be de-energized, they have amazing short circuit potential (unlike PV) and they can explode as well. Meanwhile in normal operation, they off gas poisonous fumes. >The whole industry is looking at energy storage now, as well, so this isn't just confined to the off grid fringe anymore. >Further, many industrial complexes have large battery banks for UPS systems and electric forklifts. >Why is the NEC still not making any real changes on battery storage? There have been some fairly interesting fires from utility scale battery systems, seems its more than about time. > >R.Ray Walters CTO, Solarray, Inc Nabcep Certified PV Installer, Licensed Master Electrician Solar Design Engineer 303 505-8760 On 1/23/2014 5:49 AM, Glenn Burt wrote: > > >"They can safely shut down any electrical system in a building—except for PV >systems." > >Not completely true, as batteries are stored energy systems and while they may be disconnected, are still energized regardless of the state of other systems. > > > From: David Brearley >Sent: 1/22/2014 22:48 >To: RE-wrenches >Subject: Re: [RE-wrenches] RE-wrenches Digest, Vol 7, Issue 29 > > Drake, > > >As far I know you are correct. There have not been any firefighter deaths due >to solar. > > >However, a fire chief in New Jersey did suggest that he let a warehouse burn >down due to the presence of a PV system on the roof: > > >http://www.myfoxphilly.com/story/23313172/multiple-alarm-fire > > >http://www.theatlanticcities.com/technology/2013/09/why-firefighters-are-scared-solar-power/6854/ > > >That suggests to me that while there is no crisis today, there is certainly >the potential for one down the road. Imagine the insurance industry's response >if fire fighters make a habit of not responding to structural fires due to the >presence of PV systems. Fire fighters want touch-safe PV modules. And they >have a reasonable complaint. They can safely shut down any electrical system >in a building—except for PV systems. > > >SEIA and SEPA are the solar industry lobby. Please do engage and support them. >SEIA even has a political action committee, the SolarPAC. Part of the way that >I try to stay on top of evolving Code issues is by attending SEIA- and >SEPA-sponsored events. > > >Also, over the past 4 or 5 years, the Solar America Board of Codes and >Standards has scheduled annual meetings that coincide with Intersolar. Those >are very informative sessions. I think the sessions are even archived online >at solarancs.org. > > >David Brearley >Senior Technical Editor, SolarPro magazine >NABCEP Certified PV Installation Professional >david.brear...@solarprofessional.com >Direct: 541.261.6545 > > > >On Jan 22, 2014, at 8:18 PM, re-wrenches-requ...@lists.re-wrenches.org wrote: > > >>From: Drake >> >>Subject: Re: [RE-wrenches] NEC 2014 690.12 Rapid Shutdown >> >>Date: January 22, 2014 2:16:18 PM CST >> >>To: RE-wrenches >> >>Reply-To: RE-wrenches >> >> >>David, >> >>My sincere thanks to all of you who worked to keep the module level disconnect requirement out of the 2014 code cycle. That ruling would have amounted to a knockout punch for string and central inverters on buildings. >> >>What was the driving force behind this push for immediate module level disconnection? There has clearly not been a rash of firefighter deaths due to PV systems. Although PV needs to continue evolving safety standards that take into account the concerns of firefighters, there is no crisis that would justify thwarting one of the few growing sectors of our economy. >> >>The PV track record has been amazingly good. So far, I've found no accounts of solar related firefighter deaths or injuries. The NFPA statistics show that the highest cause of firefighter death is heart attack. http://www.nfpa.org/newsandpublications/nfpa-journal/2013/july-august-2013/features/firefighter-fatalities-in-the-united-states-2012 &
Re: [RE-wrenches] Concrete tight versus raintight
>You're right that there are two types of compression connectors. I think the >rain tight ones have an extra piece near the compression ring. At Home Depot, >I believe the rain tight ones are blue and they cost a little more. See the >Halex catalog: http://www.halexco.com/products.cfm?siteSection=consumer&product_subgroup=cc&product_group=EMT Jeffrey Quackenbush___ 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
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___ 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
[RE-wrenches] NEC 2014 690.12 Rapid Shutdown
I've been going through the new Code book (which is in effect now in Massachusetts) and found myself somewhat puzzled by the intent of the new "rapid shutdown" requirement in 690.12. Does anyone have insight into how this is supposed to be interpreted and implemented? I've put together a list of my own questions, given below (the numbers reference the new 690.12 text). Thanks! 690.12 Rapid Shutdown 1. Where should the rapid shutdown switch be located? (1) only says that the shutdown function should be installed if the circuit is longer than 10’ or goes more than 5’ into a building. If this condition is fulfilled, it says nothing about where the switch should be located. (2) says that controlled conductors should be limited to 30V, 240W, which will only be the case downline from the switch, so this may mean that it should be located close to the source, i.e. on the roof. But this is just an inference, and one that doesn’t have clear boundaries; every source conductor for a series connected PV circuit (that is not Solar Edge, Enphase , etc.) will have a higher voltage and wattage potential when the sun is shining somewhere along its length, even if the disconnect is located very close to the array. Or does this requirement mean that all systems will need to have some kind of “smart” junction box, module DC-DC converter or module level AC inverter? Furthermore, individual modules often have higher voltages & wattages these days and there is no way to impose limits on their electrical characteristics in any field wired configurations. A listed AC module that sees the module leads as internal would be the only scenario that would be exempt. 2. (5) asks that equipment performing the shutdown should be listed and identified. Does that mean listed and identified for the purpose of this specific requirement? Or just listed and identified to limit voltage and wattage in 10 seconds? Does a specific UL standard exist for the function they have in mind? Does any equipment exist that has such listing and identification yet? 3. Is the rapid shutdown intended to be automatic or manual? If automatic, what are the parameters that would trigger the shutdown? If manual, are there any accessibility requirements? 4. Rapid shutdown seems more like a disconnect requirement than a circuit requirement. Why limit circuits to 30V, 240W, instead of just requiring a shutdown? Why 10 seconds, when all the disconnecting functions (i.e. manual disconnects, and internal AFCI, GFCI & UL 1740 disconnects) happen in less than a second? (It hardly seems like a “rapid” shutdown). Why write this article into section II rather than section III? ___ 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
