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  • Grounding for Rooftop system

    Looking for advice, I'm in the process of purchasing (install on Sept 4th) in NorCal :

    28 Panasonic VBHN330SA16 modules
    1 Solaredge SE7600-USS2 Inverter*
    28 Solaredge P400 optmizers
    25 year extended warranty on SE7600-US inverter
    IronRidge racking
    Critter Guard surrounding arrays <discourage unwanted critters, turkey, raccoons, bats, from roosting under roof array>
    Consumption monitoring kit SE-MTTR240-2-200-S1

    I'm concerned about grounding the system properly... What should I know, look for, ensure they are grounding according to code...
    My paranoid view is that I'm installing a lighting gatherer on my roof...
    Last edited by JRqwertyui; 08-08-2017, 12:42 PM.

  • #2
    Originally posted by JRqwertyui View Post
    Looking for advice, I'm in the process of purchasing (install on Sept 4th) in NorCal :

    28 Panasonic VBHN330SA16 modules
    1 Solaredge SE7600-USS2 Inverter*
    28 Solaredge P400 optmizers
    25 year extended warranty on SE7600-US inverter
    IronRidge racking
    Critter Guard surrounding arrays <discourage unwanted critters, turkey, raccoons, bats, from roosting under roof array>
    Consumption monitoring kit SE-MTTR240-2-200-S1

    and I'm concerned about grounding the system... What should I know, look for, ensure they are grounding according to code...
    My paranoid view is that I'm installing a lighting gatherer on my roof...
    are you sure you are getting the SE7600A-USS2? that is the storEdge inverter or the SE7600A-US

    With Ironridge at least every other rail should be tied together with bare coper wire. They should be using micro/optimizer kits for mounting the optimizers to the GROUNDED rail. The included kit will ground the optimizer to the rail. The modules should be installed with UFO-CL-001 (universal Bonding module clamp) so that the PV modules will be bonded to the grounded rail ( as well as the un-grounded rail).
    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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    • #3
      Yes, its the USS2... I wanted to future proof the inverter for future expansion for battery storage... dumb costly move, probably...
      Just to be clear, I should observe them connecting a bare copper wire to every other rail...
      Last edited by JRqwertyui; 08-08-2017, 12:53 PM.

      Comment


      • #4
        Hi JR.
        Lightning does not work that way and to relieve your worries, I would encourage you to read the introductory material on lightning.org.

        A good start for you is to read the Solar for Dummies, look at the sticky links here for links to it.

        Given that you are having this installed, the bonding installed by the contractor will comply with NEC 2014 as required in CA. The installation will be inspected by the local building department as part of the permitting process - the person doing the inspection is called the AHJ (Authority Having Jurisdiction), That said, it never hurts for you to learn more about it and the dummies guide above will give you a background.

        The National Electrical Code (NEC) 2014 version is available for free viewing online from nfpa.org but if you really want to dig into it the book costs about $100 and has all of the extensive detail - that is what your contractor is required to follow. That said, unless you are willing to spend a great deal of time reading the code - it can be hard to follow and understand - it is not a how-to type of book.

        The details of what you are asking for are significant and would be very hard to summarize in a quick post. From the list of materials above your contractor is putting together a system with good quality components.

        One question you could ask your contractor is how they are planning on dealing with 690.47(D) and ensuring your home has a single point GEC connection - that is in my opinion the single most important grounding issue for rooftop installs in the 2014 code. They should know what the number means and be able to explain it to you and understand the related issues.

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        • #5
          Originally posted by JRqwertyui View Post
          Yes, its the USS2... I wanted to future proof the inverter for future expansion for battery storage... dumb costly move, probably...
          Just to be clear, I should observe them connecting a bare copper wire to every other rail...
          Yes you should see the ground wire bonding the rails. Some installers do every single rail though that is not required.
          OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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          • #6
            Ok, back to the dummies book for further reading - that I can do.... ask about the GEC point of contact (yes, I remember that thread)...
            I'm also requesting the conduit be run inside the attic space below the upper roof where the panels will be installed, down a chase way over the garage and out to the subs and main panel... any concerns regarding the conduit runs inside the house instead of over the roof, through the eave, and down along side of the house (which I consider unappealing) ?

            also, I want to know enough during the install for my protection. The vendor hold class 'B' contractor license. not a C-10...but my due diligence has shown hundreds of both commercial and residential installs by them... with excellent feedback and reviews...
            Last edited by JRqwertyui; 08-08-2017, 05:55 PM.

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            • #7
              Hi @tyab,

              I respectfully disagree. Not to be alarmist, but roof mounted PV systems (like mine) do in fact create an elevated, electrically conductive structure that is very similar to a lightening protection system, save for the absence of the "air terminal" component. But the corner of a panel or of one of the rails can serve to "focus" the stream of ions from ground to cloud and/or cloud to ground. This effectively creates a localized reduction in the ground to air resistance to current flow.

              Contrary to what is published on lightening.org, LPS systems can and do increase the frequency (albeit very, very slightly from a statistical point of view) of localized lightning strikes to the LPS system. But it's important to remember that lightning strikes are generally very, very rare unless you live in one of the top five states (like Florida) for example.

              The grounded framing of a roof mounted PV system is just a large, very expensive lightening rod. But it is still very rare that a cloud to ground step leader will find it, and may prefer something like a proximal tree, chimney, telephone pole, etc. on it's way to the ground.

              Lightning is exactly like dragging your feet on a rub in the winter time and touching a door nob. Stored, dissimilar charges seeking the path of least resistance to neutralize each other. The question is, how likely is a strike to occur where I live, and what are the paths of least resistance near my property/PV system.

              Here's a great old text that describes (in comprehensible English -- without math) how lightening is thought to work
              https://www.nist.gov/sites/default/f...olar_cells.pdf

              Now that said lightening strikes, while common and certainly capable of causing extensive property damage, fire, and death, are still rare enough that residential property owners are not required to install LPS systems nor purchase specialty insurance. But many commercial properties are.

              It's very, very rare to see a residential property here in NJ with lightening rods (regardless of whether they have solar) unless it is a very large/expensive (several million) or historic home.

              So in general, I would say that in most parts of the country lightning strikes are rare and you shouldn't worry about it. Especially if you live in a built up urban or suburban area with lots of homes and trees. If you live in an area with an increased risk of lightening strikes, on a large flat property (farm) with few or no trees, then yes your roof mounted PV system might make a great lightening rod.

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              • #8
                "The installation will be inspected by the local building department as part of the permitting process" Do most inspectors get up on the roof? Mine did not. Just looked at the panels and disconnects.

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                • #9
                  Sorry, I know I'm going to get flamed on this. To be clear, lightening rods DO NOT attract lightning, per se. BUT, for a given square mile's likelihood to be struck by lightening at any given time for a particular storm, lightening, like all electricity, will generally prefer the path of least resistance. That could be a tree, your chimney, a golfer mid stroke with golf spikes (very common I'm sorry to say), the LPS system (preferred) or your roof mounted PV system.

                  Lightning rods work because they provide a lower resistance means of conducting the current of opposing ions from cloud to ground and ground to cloud versus the other building materials (wood, plastic, brick). Thus lightning rods reduce the localized likelihood that the structure itself serves as the conductor which can often result in a fire. So, given the likelihood of your roof to get struck by lightning, in general, if a PV system is present, it stands that it is more likely to hit (or hit proximal) to your PV system, than say your un-grounded chimney or a PVC sewer vent.

                  If you watch videos of lightning strikes in urban or commercial settings you will see multiple repeated strikes preferentially choosing good conductors -- cell towers, high voltage towers, skyscrapers / commercial buildings with lightning rods, etc. Lightning can and does strike the same place more than once, and that place is often a big peace of grounded metal sticking up in the air.

                  Comment


                  • #10
                    Originally posted by JSchnee21 View Post
                    Sorry, I know I'm going to get flamed on this..
                    Just tying this back to the OP's original question... "grounding to code" does not equate to "lightning safety", if the only code we are talking about is NEC. Grounding a SolarEdge PV system per the NEC requirements provides ground fault protection. Lightning protection, if not covered by local codes, is up to the homeowner or installer to deal with, but is probably not part of the conventional design for the area if the installer didn't offer it.

                    Font=COMIC SANS: [[FONT=comic sans ms]Queue the OP canceling his contract, yet again][/FONT]
                    Last edited by sensij; 08-08-2017, 03:44 PM.
                    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

                    Comment


                    • #11
                      Back to my original question, what should I install/connect/ask to be done in order to protect my house, equipment, etc... from lightning strikes.
                      I think its safe to assume it will attract lightning based upon the least resistance to ground... Ideally I should have both, Ground Fault Protection and Lightning - No ?
                      [I][FONT=comic sans ms]<for the record, I completely rewrote the T&Cs prior to signing and ask them (politely) to sign based upon mine plus the forums outrage as to what was listed.[/FONT][FONT=comic sans ms], and they did - I guess they are hungry for market share and agreed to all my changes, except for removal of the mechanics lean.>[/FONT][/I]
                      Last edited by JRqwertyui; 08-08-2017, 05:54 PM.

                      Comment


                      • #12
                        Originally posted by JRqwertyui View Post
                        Back to my original question, what should I install/connect/ask to be done in order to protect my house, equipment, etc... from lightning strikes.
                        I think its safe to assume it will attract lightning based upon the least resistance to ground... Ideally I should have both, Ground Fault Protection and Lightning - No ?
                        [I][FONT=comic sans ms]<for the record, I completely rewrote the T&Cs prior to signing and ask them (politely) to sign based upon mine plus the forums outrage as to what was listed.[/FONT][FONT=comic sans ms], and they did - I guess they are hungry for market share and agreed to all my changes, except for removal of the mechanics lean.>[/FONT][/I]
                        as sensij pointed out lightning protection is not enforced therefore it will most likely cost you extra.

                        I personally left #6 gauge running outside conduit from the array to the house grounding rod in hope to provide less resistance path for induced currents from nearby strikes. My understanding is in case of direct strike my equipment will be toast anyway.

                        The array presence on the roof increases probability of the strike- any sharp 'pointy' conductive object increases electrical field intensity due to small radius of its sharp end as a result greatly decreasing voltage difference the air can sustain before the strike actually happens. In other words corners of your panels do 'invite' lightning to some extent.

                        Apparently the increase in probability of the strike is not that great otherwise some rules would already be in place as PV arrays are up there for at least last 10 years. My inspectors had no comments on the subject and ignored my grounding wire.

                        Comment


                        • #13
                          LPS is not required, and in your case you do not want it. Use a Electrical Contractor who knows the codes and has experience installing Solar GT Systems. As a DIY you really do not stand a chance of installing a system correctly and up to code.

                          An LPA is not going to gain you anything, just increase your chances of being struck. Your Installer will provide a Down Conductor(s) to bond the frames with and run them outside the house to your utility service ground. By installing to code is more than sufficient protection against lightning.

                          If you are that worried about, install a tall Flag Pole or Tower out away from your home to give lightning target practice.
                          MSEE, PE

                          Comment


                          • #14
                            Originally posted by JSchnee21 View Post
                            SLightning rods work because they provide a lower resistance means of conducting the current of opposing ions from cloud to ground and ground to cloud versus the other building materials (wood, plastic, brick). Thus lightning rods reduce the localized likelihood that the structure itself serves as the conductor which can often result in a fire. So, given the likelihood of your roof to get struck by lightning, in general, if a PV system is present, it stands that it is more likely to hit (or hit proximal) to your PV system, than say your un-grounded chimney or a PVC sewer vent.
                            That is about half true, and you seem to know more than most. While true if you put up a Lightning Rods on a framed house, you have given Lightning a Planned Path to earth and out away from the protected structure. But in doing so you just greatly increased your chances of a Strike. Depending On how the house is constructed. there was likely no conductive surfaces referenced to earth before you put up the rods.

                            Rods are not going to buy you anything with panels on top, unless you now how to position each rod to put the whole structure under a Cone of Protection to ensure the rods are hit and not any point below them. But again gains you nothing with panels on top. You should be asking why?

                            Because when Rods are installed, they are Bonded to any thing conductive on the roof like Solar Panels, Raceway, Junction Boxes, Utility Cabinets, and the list goes on. So if a Rod is hit, everything on your roof is hit. However that is not much of a problem.

                            OK now let's look at the Big Picture. If you Install Solar Panels on the roof, code is going to require you bond them together, everything up there, and run Down Conductor to AC Service Ground. So if lightning strikes a Frame it has a planned path to earth outside your home. See that picture in your head?

                            OK forget solar get that out of the picture. Let's build a LPS. After we look, it will take 6 air Terminals and use 1 down conductor directly above you AC Service Meter We put all the Air Terminals at all the high points of the roof. We bond them together and run a Down Conductor to the AC Service Ground. Got that picture.

                            Now go back a grab the solar panel picture and compare it to the LPS. What do you see? A mirror image right? Why would you want to put up LPS with Solar Panels? All it does is make your wallet lighter.

                            Almost forgot. Those Cell Towers, tall buildings, trees, and such get hit by Lightning because they are the closet to the clouds, not so much because they are metal and grounded. That goes back to Cone of Protection. Put up a Tall Flag Pole away from the house and give lightning a diversion target.

                            I was fortunate in college in the late 70's. I did a Internship at Disney World in Lake Buena Vista Fl. I was a grad EE student and got in on construction of the Magic Kingdom and worked on the LPS Disney designed and installed. To this date is known among peers is still the countries best and proven LPS. Pretty slick system using Cathodic Protection of the Ground Electrodes. I really enjoyed it and got to see what no one else has seen since completion before they covered all the buildings with pavement and earth. What you see as a Park is the roof of a building under ground, or I should say a number of buildings.
                            Last edited by Sunking; 08-08-2017, 10:17 PM.
                            MSEE, PE

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                            • #15
                              One other thing. A few grounded sharp points will tend to spray off some charge before a direct
                              strike occurs. They tend to "neutralize" the potential nearby, though that is no guarantee. Bruce Roe

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