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  • Need help in evaluating replacing my existing solar panels

    Hi. I have an odd situation I need some help resolving. About 12 years ago, we installed a grid-tie solar PV installation with 36 LG 175w panels and a Fronius IG 5100 inverter. This system, has worked well, but never completely eliminated my energy bill as we have a few computer servers and now with 4 kids, burn a lot of energy. But it's saved a ton of money (and the roof has never leaked!), as here in the SF Bay Area, PGE charges an arm and a leg when you get into their band 4 or 5 pricing. The panels are all on the same 2nd story roof and point almost exactly due south, and on a clear day the system generated about 4700W in mid day.

    The IG 5100 recently failed, and in discussions with Fronius, it became clear it was going to be better to replace it with a new inverter than repair the old one, esp since the old one didn't have monitoring. The company that installed it is no longer in business on top of it all. So I got a new fronious primo 5000, and even though its pretty easy to replace myself (the inverter is in the garage, and has an ac disconnect at the panel and a separate dc disconnect next to the inverter), I like to stay compliant with code so I called an electrician to replace it.

    The electrican really didn't want to deal with the inverter programming and such,. and referred me to a solar installer that also does repairs. The issue is apparently that the wiring I have to the panels is not double insulated, which was common a decade ago, but is no longer code with a transformerless inverter like the primo. Furthermore, it appears that you can't find inverters in the 5 KW class anymore, and to redo the wiring to and between the panels would be very expensive, and I should probably replace the panels at the same time if I did that. He said the new primo would work fine if installed, but that it could not be compliant with code, so he wouldn't do it, but agreed it would probably be easy for me to do it.

    So now I am thinking about executing the original plan, and swapping out the inverter myself, which gives me pause as I like to be compliant with code, or basically redoing the entire system and installing new panels, which might be good in terms of reducing my electric bill even more.

    I'd love some advice on how to proceed, and have a few specific questions:

    1) Why is it needed to use double insulated wiring with a transformerless inverter like the primo?

    2) If I do install a new set of panels, does the 30% federal tax credit still apply if I am just replacing an existing system instead of installing one for the first time?

    3) How much cheaper would replacing the panels and wiring cost over a new installation, and could the existing roof mounts be reused? I know a more powerful system would need a bigger inverter, so I would have to factor that in as well.

    4) With 36 panels, I don't think I need to go with an expensive panel like the X21, but I the LG 315W panels seem like a good fit. Do folks have any advice for me in terms of special things to consider if I do go with new panels in a situation like mine?

    Thanks!
    Mike
    Last edited by fresnoboy; 03-19-2016, 12:35 PM.

  • #2
    This probably isn't what you wanted to hear, but:

    1) transformers provide electrical isolation. If you don't have that, adding another layer of insulation sounds like a good idea, offhand.
    2) https://www.irs.gov/pub/irs-pdf/i5695.pdf doesn't quite come out and say it, but my reading is that the credit also applies to upgrades. Ask your tax guy.
    3) ask for a bid from a couple local installers for re-using the existing panels and mounts vs. just re-using the existing mounts.
    4) if replacing panels, let the installer suggest the exact model of panel, he'll have a favorite, and it'll probably be ok.

    Then toss any bids from vendors that look cheesy, calculate the payback time for the remaining bids, and if it's reasonable, go for it!

    Note that rate changes are on their way, so predicting future costs might be complicated.
    Check to see how soon your utility is switching to the new net metering tariff (probably http://www.pge.com/en/mybusiness/sav...ing/index.page ), the old tariff will pay off faster if you can still get it.

    (BTW I may be facing a similar issue sometime -- I used 175 watt panels in 2008 -- but at least my installer's still in business. Now I want to go check my wiring to see if it's double-insulated

    Comment


    • #3
      What is the specific insulation rating of the wiring?... both on the roof, and in the connection to the inverter. They are typically not the same. CA is still based on NEC 2011, so you might still be OK.
      CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

      Comment


      • #4
        Thanks everyone.

        I do believe the tax credit applies to the upgrade, but will verify with my accountant.

        I have the old E6 TOU tariff in place already, as part of the existing system. If I read the PGE site properly that you linked to, it appears sometime in 2016 the program expires, but there is a pretty long transition period where things stay the same. If I were to upgrade the panels now, before the program ended, would the start of the transition period date be reset from 2006 to 2016? That might not be a bad thing to do. Obviously, if we upgraded the panels post the end of the program, that would be a bad thing because it appears if you add more than 10% additional capacity you immediately transition to the new (not very good) plan.

        If I upgrade the panels, does that require another round of certification from PGE? E6 is not available to new users after March 1 of this year, so would upgrading the system trigger a change in rate?


        I haven't been on the roof do I can't say what the wiring looks like. I am unclear what the change was to the rules that require the double insulation in case of a transformerless inverter. DOes anyone here have specifics on that?

        thanks!
        Mike


        Comment


        • #5
          What the electrician is probably referring to is NEC 2011 690.35(D), which specifically applies to Ungrounded Photovoltaic Power Systems

          (D) The photovoltaic source conductors shall consist of the
          following:
          (1) Nonmetallic jacketed multiconductor cables
          (2) Conductors installed in raceways, or
          (3) Conductors listed and identified as Photovoltaic (PV) Wire installed as exposed, single conductors.

          What may be currently installed is probably compliant with 690.31(B), which allows USE-2.

          690.31(B)
          (B) Single-Conductor Cable. Single-conductor cable type
          USE-2, and single-conductor cable listed and labeled as
          photovoltaic (PV) wire shall be permitted in exposed outdoor
          locations in photovoltaic source circuits for photovoltaic
          module interconnections within the photovoltaic array.
          You could just replace the inverter with another transformer based model... the SMA Sunny Boy 5000-US is still readily available, and should be electrically compatible with your array design (although you should verify it before going too far).

          With respect to your other questions, at least under NEM 1.0, any changes to your system should not affect your eligibility for the E6 rate plan. PG&E may hit the NEM 1.0 cap at the end of the year, and it isn't entirely clear yet what tariffs will be available at that time.

          I don't think you will be able to reset the grandfathering period of your system under NEM 1.0 by increasing the capacity more than 10%. My understanding is that the original capacity will still have the original in-service date, and only the new capacity will get the new in-service date. Even if you make the upgrade after the cap, the CPUC has stated the grandfathering of the original array is unaffected, and the new NEM tariff will only apply to the new capacity, unless you choose to take the new tariff for your entire system. It isn't clear how the power companies will handle having portions of systems under two different NEM tariffs.

          Edit:
          If you do end up upgrading panels, you might save some labor and materials by having racks in place. One potential problem is that fire regulations have changed, and PV systems are certified as a rack+panel system to get the proper fire rating now. You will need to figure out what type of racks and mounting were used, and see if it can be combined with your new panels to get the appropriate rating. If not, you will probably have to replace the racks too, which means your retro-fit cost will probably be very close to the cost of new installation. Even if racks and conduit can be reused, I would not expect much more than a 10% discount off a new install price. You will need fewer panels to max out your 5k inverter, so they might actually have to pull up some racking and do roof repair where the mounts used to be.
          Last edited by sensij; 03-19-2016, 02:56 PM.
          CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

          Comment


          • #6
            What constitutes PV wire? Does it have to be double insulated? Mine isn't. The wire I bought for my diy installation is purportedly rated for both USE-2 and PV. It is UL 4703 listed PV direct burial (see attached, I cut a piece of the insulation off and it's definitely not double insulated).
            Here's where I bought it:
            http://www.wireandcabletogo.com/Copp...4703-Wire.html

            Is this wire compliant under NEC 2014?
            Maybe the Op's wire is rated for PV?
            Last edited by DaveDE2; 03-19-2016, 04:43 PM.

            Comment


            • #7
              Your wire is PV wire per the label, and should be fine for all PV installations. "Double-insulated" isn't really a thing, but sort of describes what makes PV wire different from standard wire.

              From http://solarprofessional.com/article...ble_pagination

              As the name suggests, PV Wire is designed for making PV module interconnections, specifically where single conductors are run outside raceways or conduits and exposed to a unique set of physical and environmental abuses. PV Wire differs from USE-2 in that it uses thicker insulation or a jacket to provide additional mechanical protection. As a result, PV Wire has greater sunlight resistance and can better withstand extreme cold than USE-2. Because of these improved physical properties, PV Wire can be rated for use at higher voltages than USE-2, such as 1,000 volts versus 600 volts. PV Wire can also be used in applications where USE-2 cannot, such as in ungrounded PV array source circuits.
              No, USE-2 wouldn't be compliant for an ungrounded system under NEC 2014 either. PV wire wasn't really common when the OP's system was installed (there were no transformerless inverters), and there is a good chance the electrician is correct that the existing wiring would not be code compliant for an ungrounded system.
              CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

              Comment


              • #8
                Maybe the electrician was referring to the existing wire as not being UL 4703 listed and he just said it wasn't double insulated pv wiring.

                Comment


                • #9
                  Originally posted by sensij View Post
                  Your wire is PV wire per the label, and should be fine for all PV installations. "Double-insulated" isn't really a thing, but sort of describes what makes PV wire different from standard wire.

                  From http://solarprofessional.com/article...ble_pagination



                  No, USE-2 wouldn't be compliant for an ungrounded system under NEC 2014 either. PV wire wasn't really common when the OP's system was installed (there were no transformerless inverters), and there is a good chance the electrician is correct that the existing wiring would not be code compliant for an ungrounded system.


                  Actually, the original Fronius IG 5100 is a transformerless inverter, it was one of the first, and had a higher efficiency rating at the time. Does that mean that wiring installed may actually be UL 4703 compliant?

                  Was all this changed in the NEC in 2011? I had never heard of "PV wire" until I started the process of replacing the IG 5100.

                  PS No electrician has actually looked at the wire yet. Everyone is just telling me I can't use the new inverter because the wiring used back in 2006 is non-compliant. Its hard to tell what actual wiring is being used because all the exposed runs in the attic or the garage leading to the inverter are in EMT or are armored cable. I'd have to climb up to the 2nd story roof and look at the wiring under the panels to tell.

                  Thanks,
                  Mike
                  Last edited by fresnoboy; 03-19-2016, 05:16 PM.

                  Comment


                  • #10
                    With the number of panels you have, they must be wired in multiple strings and then joined in a fused combiner. The combiner might be on the roof, or maybe inside the attic. The PV wire requirement is only for exposed wiring on the roof, anything in conduit should be fine.
                    Last edited by sensij; 03-19-2016, 06:16 PM.
                    CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

                    Comment


                    • #11
                      Going up on the roof and examining the wire is going to be difficult to determine whether it's PV or USE-2. Since your original inverter is transformerless and you're up for replacing it yourself, if it were me, I'd just do it. That doesn't affect the original wiring and should not call for new wiring code compliance for things you are not altering.

                      Comment


                      • #12
                        The Fronius IG 5100 does not appear to be transformerless. That isn't really the distinction that matters... the different requirements of code apply based on whether the system is grounded or not. From what I've seen, prior to the Primo, Fronius inverters relied on a fuse between the DC- and ground to provide ground fault protection. This means that whether the DC side was grounded with a GEC or not, the DC- is ground referenced and will act like a grounded system. The Primo uses different techniques for GFP that allow both the DC- and DC+ to float, and it is that ungrounded design that requires the PV rated conductors. That requirement was introduced in NEC 2005, which is the basis for CA Electric Code 2007. Systems installed before 2008 weren't subject to this requirement, and it isn't likely PV wire was used.


                        CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

                        Comment


                        • #13
                          Originally posted by sensij View Post
                          The Fronius IG 5100 does not appear to be transformerless. That isn't really the distinction that matters... the different requirements of code apply based on whether the system is grounded or not. From what I've seen, prior to the Primo, Fronius inverters relied on a fuse between the DC- and ground to provide ground fault protection. This means that whether the DC side was grounded with a GEC or not, the DC- is ground referenced and will act like a grounded system. The Primo uses different techniques for GFP that allow both the DC- and DC+ to float, and it is that ungrounded design that requires the PV rated conductors. That requirement was introduced in NEC 2005, which is the basis for CA Electric Code 2007. Systems installed before 2008 weren't subject to this requirement, and it isn't likely PV wire was used.


                          Thanks. This makes sense to me.

                          I did open up the DC disconnect switchbox, and there are three wires coming down from the panels. The +, which is switched through the switchbox, the negative, and a ground wire, which is connected to the box's ground (and the EMT conduit that the DC wiring runs through to the box), and then the ground wire is also routed through plastic conduit to the IG 5100. I thought the PV system wiring usually didn't include a ground wire. Does this indicate something about how the system is wired?

                          The wire is AWG8, type "MTW or THMN or THWN-2 or T90, etc...)

                          Thanks!
                          Mike




                          Comment


                          • #14
                            A equipment ground conductor to ground the frames on the modules and the racking is required, and is probably the ground wire you see.

                            THWN-2 is appropriate for the run from the combiner to the inverter, in conduit or physically protected. You can leave that run along, except if you increase the capacity of the array it might be too small to carry the additional power without help.

                            The USE-2 or PV wire should only be in the unprotected runs between panels and to the string combiner, where it would transition to conduit with the THWN-2.

                            One other slight concern would be the type of wire used on the panel leads. I couldn't find any documentation on a LG 175 W panel to see what might have been used. All panels going up today have PV wire leads.
                            CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

                            Comment


                            • #15
                              Originally posted by sensij View Post
                              A equipment ground conductor to ground the frames on the modules and the racking is required, and is probably the ground wire you see.

                              THWN-2 is appropriate for the run from the combiner to the inverter, in conduit or physically protected. You can leave that run along, except if you increase the capacity of the array it might be too small to carry the additional power without help.

                              The USE-2 or PV wire should only be in the unprotected runs between panels and to the string combiner, where it would transition to conduit with the THWN-2.

                              One other slight concern would be the type of wire used on the panel leads. I couldn't find any documentation on a LG 175 W panel to see what might have been used. All panels going up today have PV wire leads.
                              Got it. So the Primo not only doesn't need the ground fault fuse between the DC- and ground, it actually wouldn't work properly if there was a fuse in the system between the DC - and the frame ground? I did notice in the wiring diagram, the Primo doesn't have an explicit frame ground connector like the IG 5100 did. It sounds like the ground would just not be connected to anything at all if it was hooked up in the normal way, other than maybe the ground coming through the conduit? The wiring diagram does indicate ground from frame and racks is connected to the Primo, just not through an explicit connector it seems.

                              Thanks!
                              Mike


                              Comment

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