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  • PV wires on roof surface

    Hi there,

    I am an inspector, and on a PV job I was looking at the other day, all the wiring was left lying on the roof surface. The roof was near-flat, with a painted-on-metal finish. The array was quite low, perhaps 4" off the surface.

    I am quite clear that this is not optimal, but actual code is a bit less definitive: I think it comes down to "workmanlike manner" language.

    Anyway, I'd be interested in hearing other's opinions of how important this detail is.

    K

  • #2
    Originally posted by GreenCodeInspector View Post
    Hi there,

    I am an inspector, and on a PV job I was looking at the other day, all the wiring was left lying on the roof surface. The roof was near-flat, with a painted-on-metal finish. The array was quite low, perhaps 4" off the surface.

    I am quite clear that this is not optimal, but actual code is a bit less definitive: I think it comes down to "workmanlike manner" language.

    Anyway, I'd be interested in hearing other's opinions of how important this detail is.

    K
    First question, of course, is what kind of wire was used.
    Clearly it has to be suitable for both wet conditions and sun exposure. The new PV wire type will meet both of those conditions (although any color but black may end up white in a year). And its thicker insulation will resist abrasion better than any other unjacketed wire type.
    The next concern would be the ever popular "subject to physical damage" provision.
    Finally, the temperature correction required for ampacity will be somewhere between non-roof ambient and the NEC temperature adder for conduit exposed on rooftop.

    Enjoy!
    SunnyBoy 3000 US, 18 BP Solar 175B panels.

    Comment


    • #3
      The wire has to be secured also, so it will not flex and flap in the wind. And have UV rated insulation.
      Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
      || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
      || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

      solar: http://tinyurl.com/LMR-Solar
      gen: http://tinyurl.com/LMR-Lister

      Comment


      • #4
        Sloppy job that can abrade in the wind. Enphase for one is quite clear in their installation cut-sheets that trunk wiring must be dressed so it doesn't lie on the roof. I'm surprised it passed the original inspection.
        4KW system featuring Suniva OPT265/Enphase M215

        Comment


        • #5
          Is it a single conductor, or multi-conductor wire/cable? That will tell you what you want to know in NEC 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. Exception: Raceways shall be used when required by 690.31(A).
          MSEE, PE

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          • #6
            Thanks for your thoughts everyone. It's single conductor, USE-2 I believe (could be PV). It's not secured anywhere, long lengths of it plus connectors are flopping around on the roof.

            This was the first inspection, this wasn't the worst part, but it's complicated by not having any direct and irrefutable code applying to it, as far as I can see. I think that's changing in the 2014 NEC, btw.

            So far as I know the wire was sized correctly.

            Comment


            • #7
              That sounds like a hack job to me...

              The electrical inspector up here in Burlington VT will not pass the job if there are wires touching the roof. Not sure what code reference she uses (if any) but the general idea is if the wires are rubbing on the roof, they will fail prematurely.

              Comment


              • #8
                Originally posted by GreenCodeInspector View Post
                Thanks for your thoughts everyone. It's single conductor, USE-2 I believe (could be PV). It's not secured anywhere, long lengths of it plus connectors are flopping around on the roof.

                This was the first inspection, this wasn't the worst part, but it's complicated by not having any direct and irrefutable code applying to it, as far as I can see. I think that's changing in the 2014 NEC, btw.

                So far as I know the wire was sized correctly.
                I do not believe any version of the NEC would allow long lengths of wire to just be lying on a surface. Usually PV wires are tie wrapped or secured to the PV panels or racks. They can be exposed to sunlight if they are rated for outdoor installation but still needs to be secured every few feet or so.

                Comment


                • #9
                  Originally posted by SunEagle View Post
                  I do not believe any version of the NEC would allow long lengths of wire to just be lying on a surface. Usually PV wires are tie wrapped or secured to the PV panels or racks. They can be exposed to sunlight if they are rated for outdoor installation but still needs to be secured every few feet or so.
                  Any wires or cables which are not in raceways and are not fished through walls need to be supported and secured at minimum intervals.
                  You may not find that particular requirement in the sections dealing specifically with USE-2 or with PV wire though.
                  SunnyBoy 3000 US, 18 BP Solar 175B panels.

                  Comment


                  • #10
                    Originally posted by inetdog View Post
                    Any wires or cables which are not in raceways and are not fished through walls need to be supported and secured at minimum intervals.
                    You may not find that particular requirement in the sections dealing specifically with USE-2 or with PV wire though.
                    Going by memory is not working well with me anymore so I have to go back and read my code book tomorrow at work.

                    I would think (maybe a pipe-dream) that even though "securing lose wire and cable" is not specifically mentioned when discussing PV wire there would be some type of reference in Article 690 pointing to those requirements, especially for wires energized above 50 volts.

                    I just found something concerning the 2008 NEC Article 690.31(A) "Where photovoltaic source and output circuits operating at a maximum system voltages greater than 30 volts are installed in readily accessible locations, circuit conductors shall be installed in a raceway."

                    Maybe "on the roof" is not considered an accessible location or maybe all of those loose wires have less than 30 volts in them.

                    I also found an article concerning the "Inspecting Photovoltaic (PV) Systems for Code-Compliance" which is provided by a Mr. Bill Brooks, PE from Brooks Engineering which provides some detail on the 2005 and 2008 NEC Article 690 code.

                    Moderators. If this reference is not a good one please delete it. Thanks
                    Last edited by SunEagle; 09-01-2014, 04:53 PM. Reason: added 2008 NEC code sentence

                    Comment


                    • #11
                      Originally posted by SunEagle View Post
                      Going by memory is not working well with me anymore so I have to go back and read my code book tomorrow at work.

                      I would think (maybe a pipe-dream) that even though "securing lose wire and cable" is not specifically mentioned when discussing PV wire there would be some type of reference in Article 690 pointing to those requirements, especially for wires energized above 50 volts.

                      I just found something concerning the 2008 NEC Article 690.31(A) "Where photovoltaic source and output circuits operating at a maximum system voltages greater than 30 volts are installed in readily accessible locations, circuit conductors shall be installed in a raceway."

                      Maybe "on the roof" is not considered an accessible location or maybe all of those loose wires have less than 30 volts in them.
                      If the wire is USE-2, then you have a problem with using it on the roof, supported or not:
                      338.12 tells us that USE shall not be used
                      For aboveground installations except where USE cable emerges from the ground and is terminated in an enclosure at an outdoor location and the cable is protected in accordance with 300.5(D)
                      Now USE-2 wire may well be cross listed as another wire type (such as RRH or RHW), in which case the limitations on that wire type in 310 need to be observed.
                      In the 2011 Code, type PV wire is not specifically recognized in Chapter 3 at all, but the provisions in 690 will override those in Chapter 3 when there is a conflict, and PV wire is specifically mentioned in 690.
                      I would be also be tempted to try applying 690.31(A), even though it might be stretching "readily accessible":
                      ...
                      Where photovoltaic source and output circuits operating at maximum system voltages greater than 30 volts are installed in readily accessible locations, circuit conductors shall be installed in a raceway.....
                      In [2011], 690.31(B) gets more specific, especially the Exception at the end of it:
                      (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.
                      Exception: Raceways shall be used when required by 690.31(A).
                      (Emphasis mine)
                      Unfortunately, I have not been able to find anything specific about support when used outside a raceway outdoors either.
                      SunnyBoy 3000 US, 18 BP Solar 175B panels.

                      Comment


                      • #12
                        Originally posted by inetdog View Post
                        If the wire is USE-2, then you have a problem with using it on the roof, supported or not:
                        338.12 tells us that USE shall not be used
                        Now USE-2 wire may well be cross listed as another wire type (such as RRH or RHW), in which case the limitations on that wire type in 310 need to be observed.
                        In the 2011 Code, type PV wire is not specifically recognized in Chapter 3 at all, but the provisions in 690 will override those in Chapter 3 when there is a conflict, and PV wire is specifically mentioned in 690.
                        I would be also be tempted to try applying 690.31(A), even though it might be stretching "readily accessible":
                        In [2011], 690.31(B) gets more specific, especially the Exception at the end of it:

                        (Emphasis mine)
                        Unfortunately, I have not been able to find anything specific about support when used outside a raceway outdoors either.
                        I saw that "within the photovoltaic array" reference so you would think that the panels would protect the exposed wires but they should still be secured to the framework or panels in some way.

                        Comment


                        • #13
                          Originally posted by SunEagle View Post
                          I saw that "within the photovoltaic array" reference so you would think that the panels would protect the exposed wires but they should still be secured to the framework or panels in some way.
                          Maybe running across the surface of roof takes them outside (the vertical limits of) the PV array?
                          SunnyBoy 3000 US, 18 BP Solar 175B panels.

                          Comment


                          • #14
                            Originally posted by inetdog View Post
                            Maybe running across the surface of roof takes them outside (the vertical limits of) the PV array?
                            Hmmm. Pictures would help with this discussion.

                            Comment


                            • #15
                              If you using TL inverters with ungrounded arrays, USE-2 is not acceptable. You must use PV Wire and it cannot be white or gray as no conductor is grounded.

                              The wiring must be secured and not touch the roof.

                              The Bill Brooks article provides some good information.

                              Andy

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