Announcement

Collapse
No announcement yet.

Running 6awg solid copper along Ironridge aluminum racking? Dissimilar metal issue?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Running 6awg solid copper along Ironridge aluminum racking? Dissimilar metal issue?

    Hey everyone, I am finishing up with my install and just have to finalize the rail grounding. I am using Ironridge and Panasonic panels. The ground wire clams are from Ironridge (I believe stainless steel to avoid corrosion). But as I run the wire down to the Jbox the wire may be touching the rails (As it runs across them) and also the panel frame (as I am trying to run it underneath the panels to give it some protection from the elements (if minimal, better than none), anyhow, what if the wire touches the panel's frame (which I believe is aluminum).

    Basically at these points where the bare 6AWG ground wire is running down to the jbox, do I need to worry about corrosion? If so, what steps can I take to prevent it (other than re-running with sheathed wire).

  • #2
    You're an engineer, right ?

    If you're considering galvanic corrosion, and are curious to learn something, start with a lool look at a galvanic table.

    Also, a 5 min. or less Google search will give you a lot of info to self answer your question.

    A couple examples of general pieces on PV system grounding and bonding: See a Solar Power World articles from 04/09/2012 an 08/10/2015 on line. Not the final say, but a start.

    As an opinion, occasional and point contact w/out fastening of a Cu ground to an Al panel frame probably isn't a large source of corrosion, but I'd consider measures to minimize/isolate the grounding wire from either unintentional contact w/the frames or any flapping in the breeze or other movement while still accounting for thermal expansion as a matter of good design.

    At the clamps/fasteners, because CU is slightly anodic to (less noble than) St. Stl., that situation may have some potential for perhaps slight but noticeable galvanic corrosion of the grounding rod. As a practical matter, such corrosion doesn't seem to be much of a problem, but installers reading this probably have more better information on than.

    Take what you want of the above. Scrap the rest.

    Comment


    • #3
      Originally posted by J.P.M. View Post
      You're an engineer, right ?
      Yes, doesnt apply here though. I know what happens if you bond aluminum to copper. What I asked is not covered in NEC or CEC.

      Originally posted by J.P.M. View Post
      If you're considering galvanic corrosion, and are curious to learn something, start with a lool look at a galvanic table.

      Also, a 5 min. or less Google search will give you a lot of info to self answer your question.

      A couple examples of general pieces on PV system grounding and bonding: See a Solar Power World articles from 04/09/2012 an 08/10/2015 on line. Not the final say, but a start.
      Already did, but this information is not relevant to the question. I am not bonding or splicing aluminum with copper. This is a very specific scenario, both panel frames and the rails are coated. I want to know specifically in this scenario if there is anything to worry about. As in, I am looking for actual field/personal experience with people laying bare Cu on top of anti-corrosion coated Al rails.

      Originally posted by J.P.M. View Post
      As an opinion, occasional and point contact w/out fastening of a Cu ground to an Al panel frame probably isn't a large source of corrosion, but I'd consider measures to minimize/isolate the grounding wire from either unintentional contact w/the frames or any flapping in the breeze or other movement while still accounting for thermal expansion as a matter of good design.

      At the clamps/fasteners, because CU is slightly anodic to (less noble than) St. Stl., that situation may have some potential for perhaps slight but noticeable galvanic corrosion of the grounding rod. As a practical matter, such corrosion doesn't seem to be much of a problem, but installers reading this probably have more better information on than.

      Take what you want of the above. Scrap the rest.
      This is more of what I was looking for. Thanks.

      Comment


      • #4
        I was advised to protect the bare copper wire from contact with aluminum rails using pieces of plastic tubing, at the point they meet, held in place with cable ties. If you already have the copper in place, you could slit plastic tubing to make it easy to place over the wire.

        It's best to use UV stable tubing and UV stable cable ties, even though it will be shielded from the sun by the panels.

        One common source of appropriate plastic tubing is exterior electrical cable jacket, such as the jacket surrounding Enphase Q cable or similar solar panel cable.
        7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

        Comment


        • #5
          Hi All,

          I know Iam in a whole other country but we never use bare wire on anything, ever, period, not sure why you would. Perhaps a US installer will chime in, cheers

          Comment


          • #6
            Originally posted by solar pete View Post
            Hi All,

            I know Iam in a whole other country but we never use bare wire on anything, ever, period, not sure why you would. Perhaps a US installer will chime in, cheers
            I am not an installer, but in the US it is common to use bare copper on ground wires inside junction boxes and on solar installations but not in conduit.
            Last edited by Ampster; 03-09-2020, 07:47 PM.
            9 kW solar. Driving EVs since 2012

            Comment


            • #7
              SolarPete makes a great point. Even thoug we allow bare ground wire in the US, insulating it is always better. It will be better protected from corrosion, from damage, and from accidential contact to something live nearby. All three SHOULD be very low probability, but lower risk is always nice.
              7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

              Comment


              • #8
                Originally posted by solar pete View Post
                Hi All,

                I know Iam in a whole other country but we never use bare wire on anything, ever, period, not sure why you would. Perhaps a US installer will chime in, cheers
                The only reason I heard was that insulation will get destroyed by the sun anyways, you would need a really specialized cable that is UV/Sun resistant, but you are compromising that insulation anyways by cutting it off at parts to bond it to the array/rails. Im in California, sun here is very harsh, even UV/sun resistant stuff gets pretty messed up over time.

                Cost may be another reason? 25ft (7.62 meters) of 6AWG (4.11 mm) of solid bare copper is $20 USD.

                Comment


                • #9
                  How long will a common garden hose last out in the sun? Perhaps 5 years? You could buy a short one for $20 and cut pieces from that for insulation. It will be under the panels, so less exposed than if in the garden, so it will last 20 years. When it finally rots away to nothing, then you're faced with wire to aluminum contact, which will only last another 5 or 10 years.

                  Or you could go to an auto parts store and buy cut lengths of top-quality rubber hose. That will last a long time under the panels.

                  Or you could get the right stuff: The link below is for #6 insulated stranded (flexible) green wire UV resistant from Lowe's for $0.88 per foot. That's not much more expensive than the bare wire you mentioned ($0.80 per foot), and you can get exactly as much as you need, saving waste.

                  https://www.lowes.com/pd/Southwire-S...e-Foot/3129537
                  7kW Roof PV, APsystems QS1 micros, Nissan Leaf EV

                  Comment


                  • #10
                    Originally posted by bob-n View Post
                    How long will a common garden hose last out in the sun? Perhaps 5 years? You could buy a short one for $20 and cut pieces from that for insulation. It will be under the panels, so less exposed than if in the garden, so it will last 20 years. When it finally rots away to nothing, then you're faced with wire to aluminum contact, which will only last another 5 or 10 years.

                    Or you could go to an auto parts store and buy cut lengths of top-quality rubber hose. That will last a long time under the panels.

                    Or you could get the right stuff: The link below is for #6 insulated stranded (flexible) green wire UV resistant from Lowe's for $0.88 per foot. That's not much more expensive than the bare wire you mentioned ($0.80 per foot), and you can get exactly as much as you need, saving waste.

                    https://www.lowes.com/pd/Southwire-S...e-Foot/3129537
                    My AHJ requires it to be solid copper because they say that the insulation will weather away, then you have bare stranded wire, which is bad news. Plus stranded would introduce new challenges, as it would droop down to the roof surface if not supported at very short intervals.

                    Comment

                    Working...
                    X