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Best Mounting Option for Rock-Covered Roof?

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  • Best Mounting Option for Rock-Covered Roof?

    Hi everyone. I must admit that these solar panels are not for my home, but rather my office, but since the question is regarding installation, I hope it is okay that I'm posting it here.

    I own a small warehouse space that's part of a bigger complex. The roof is a layer of loose rock (the kind you see in front of homes) with sheet metal underneath. Given that most of the options available seem to be designed for roofs that are already tilted, I'm having a hard time deciding on a mounting option for my two solar panels. I specifically am hoping for something to tilt the solar panels to the appropriate angle (I'm near Denver and I've been told that your latitude is your best bet for tilt angle) that is safe. I've already checked with the property management company to make sure it is okay for the panels to go on the roof. They've also said that the roof should easily support the weight, but to perhaps leave them about 5-10 feet apart on the roof just to be safe.

    They are both REC Peak Energy series, and they are 39" by 65 1/2" by my measurements. We have an excellent view of the southern sky with absolutely no blockage from trees or other obstacles, so I'm open to the idea . What are your suggestions for a mounting system that would work?

    Happy to answer any questions about anything I've missed.

  • #2
    Angled racking is readily available for tilting. As for affixing to a roof, and I say this with caution, with only 2 panels, a ballasted support system may be an option, particularly if fixation can be achieved without roof penetrations, but that may be tricky and costly. Whether fixed via penetrations or ballasted, wind loadings on the roof and the panel support structure will need to be considered and the roof will need to be checked for concentrated loadings from any ballast if that method is used.

    Comment


    • #3
      Originally posted by Off Grid View Post
      Hi everyone. I must admit that these solar panels are not for my home, but rather my office, but since the question is regarding installation, I hope it is okay that I'm posting it here.

      I own a small warehouse space that's part of a bigger complex. The roof is a layer of loose rock (the kind you see in front of homes) with sheet metal underneath. Given that most of the options available seem to be designed for roofs that are already tilted, I'm having a hard time deciding on a mounting option for my two solar panels. I specifically am hoping for something to tilt the solar panels to the appropriate angle (I'm near Denver and I've been told that your latitude is your best bet for tilt angle) that is safe. I've already checked with the property management company to make sure it is okay for the panels to go on the roof. They've also said that the roof should easily support the weight, but to perhaps leave them about 5-10 feet apart on the roof just to be safe.

      They are both REC Peak Energy series, and they are 39" by 65 1/2" by my measurements. We have an excellent view of the southern sky with absolutely no blockage from trees or other obstacles, so I'm open to the idea . What are your suggestions for a mounting system that would work?

      Happy to answer any questions about anything I've missed.
      if you don't mind to step back a little:
      - what is the purpose of the system? I understand it consists of 2 panels 250-330 watt each so I wonder what original problem are you trying to solve.
      - please let us know the exact model number of the panels; their wattage is usually part of that number

      PVWatts provides good model which allows you to enter location, panels, azimuth and tilt and see what approx output in kWh you can expect from the system. Latitude as tilt angle is a good starting point. Please enter your parameters there and post back kWh PVWatts returns along with your local electricity rates so it would be clearer what are we dealing with.

      Comment


      • #4
        Originally posted by max2k View Post

        if you don't mind to step back a little:
        - what is the purpose of the system? I understand it consists of 2 panels 250-330 watt each so I wonder what original problem are you trying to solve.
        - please let us know the exact model number of the panels; their wattage is usually part of that number

        PVWatts provides good model which allows you to enter location, panels, azimuth and tilt and see what approx output in kWh you can expect from the system. Latitude as tilt angle is a good starting point. Please enter your parameters there and post back kWh PVWatts returns along with your local electricity rates so it would be clearer what are we dealing with.
        The purpose of the system is to set up a small class 2 lighting system with LED. We're still working out the exact details, but we have our wattages figured out and are just deciding on which LEDs we want to use. As stupid as this sounds, the electricity savings is not a concern here. We're not looking to save for our own facility (although added benefits never hurt), we are doing this to test a low-scale model and play with a technology we're interested in but don't know much about.

        The model number is REC260PE Z-Link. I found an install guide for REC, but I'm not sure it's specific to this model.

        I'm going to post my results in another reply because they're long and I want them to be obvious. This is just my first run through on it, and I plan to do a couple more tests, but I think these results will be fine for now. Thanks for pointing me to PVWatts, what a great tool!

        Comment


        • #5
          4.30 57 6
          4.74 57 6
          5.97 78 9
          5.96 73 8
          5.58 70 8
          5.46 65 7
          5.42 65 7
          5.86 70 8
          5.75 68 8
          4.88 61 7
          5.17 65 7
          2.88 40 4
          5.16 769 $ 85
          DC System Size .52 kW
          Module Type Standard
          Array Type Fixed (roof mount)
          Array Tilt

          Comment


          • #6
            Originally posted by J.P.M. View Post
            Angled racking is readily available for tilting. As for affixing to a roof, and I say this with caution, with only 2 panels, a ballasted support system may be an option, particularly if fixation can be achieved without roof penetrations, but that may be tricky and costly. Whether fixed via penetrations or ballasted, wind loadings on the roof and the panel support structure will need to be considered and the roof will need to be checked for concentrated loadings from any ballast if that method is used.
            This area gets some pretty unpredictable weather, so I'm almost positive we're going to need to have a fixed design. The wind is usually calm, but it gets upwards of 90MPH at least a few times a year. The other problem is that the sheet metal isn't completely flat, so we're going to have to be strategic about the length. I'll try to climb up there today and get a measurement of the width between the high points of the metal if that would be helpful at all. I saw a solution on an Instrcutable where a guy had a welder custom-make his solar stand, complete with the tilt angle he was looking for. Do you think I should consider that as a possible solution, or would we be better off sticking to a trusted mounting system?

            Comment


            • #7
              Originally posted by Off Grid View Post

              This area gets some pretty unpredictable weather, so I'm almost positive we're going to need to have a fixed design. The wind is usually calm, but it gets upwards of 90MPH at least a few times a year. The other problem is that the sheet metal isn't completely flat, so we're going to have to be strategic about the length. I'll try to climb up there today and get a measurement of the width between the high points of the metal if that would be helpful at all. I saw a solution on an Instrcutable where a guy had a welder custom-make his solar stand, complete with the tilt angle he was looking for. Do you think I should consider that as a possible solution, or would we be better off sticking to a trusted mounting system?
              I'd consider a reevaluation of the project. Local codes may very well require some formal review of the design for structural considerations. That may require a P.E. review and sign off, maybe not. These look like considerations you are unfamiliar with. If required, they might get expensive relative to what you'll save, or the project budget.

              Comment


              • #8
                Good flat roof. Rocks. Experimental system. Ballast is the way to go. How much, and what form of, ballast is the question. And pretty sure someone here knows, just not me. As far as tilt, yes you want the panels tilted for latitude, if you want adjustable tilt go for it if someone wants to climb up there 2x or 4x per year to adjust it.
                Last edited by AzRoute66; 08-23-2017, 12:34 PM.

                Comment


                • #9
                  Originally posted by Off Grid View Post

                  The purpose of the system is to set up a small class 2 lighting system with LED. We're still working out the exact details, but we have our wattages figured out and are just deciding on which LEDs we want to use. As stupid as this sounds, the electricity savings is not a concern here. We're not looking to save for our own facility (although added benefits never hurt), we are doing this to test a low-scale model and play with a technology we're interested in but don't know much about.

                  The model number is REC260PE Z-Link. I found an install guide for REC, but I'm not sure it's specific to this model.

                  I'm going to post my results in another reply because they're long and I want them to be obvious. This is just my first run through on it, and I plan to do a couple more tests, but I think these results will be fine for now. Thanks for pointing me to PVWatts, what a great tool!
                  If the point is to learn electrical performance panels can be temporarily put pretty much anywhere but any long lasting installation will be subject to unexpected storms and rightfully require to be done to local codes and regulations. You don't want your panel to fly off the roof in that 90mph wind and kill someone on the ground or even tear off chunk of the roof. If you want to see what's involved in installing such system then I'd advise to stick to the existing local rules as they were put there based on prior bad experiences. Meeting requirements of those rules would probably define the cost of such project. I'd simply go to local building department and have a talk with engineers there before buying anything.

                  Comment


                  • #10
                    Originally posted by max2k View Post

                    If the point is to learn electrical performance panels can be temporarily put pretty much anywhere but any long lasting installation will be subject to unexpected storms and rightfully require to be done to local codes and regulations. You don't want your panel to fly off the roof in that 90mph wind and kill someone on the ground or even tear off chunk of the roof. If you want to see what's involved in installing such system then I'd advise to stick to the existing local rules as they were put there based on prior bad experiences. Meeting requirements of those rules would probably define the cost of such project. I'd simply go to local building department and have a talk with engineers there before buying anything.
                    If this is a test or experimental solution you don't want it attached to the building in any way. mount it on the ground with a few posts.
                    You have way too many permits, and structural issues to deal with on that roof to even consider doing such a small system that is never going to save a penny up there.
                    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

                    Comment


                    • #11
                      Thanks for all this feedback, guys. I hadn't even thought of building codes, and after looking into them, I think that would be a disastrous way of going about this. It sounds like we're going to try ButchDeal's solution and just hook it up on the ground, and if it becomes feasible, we may look into creating a larger array and looking into the codes. Thanks again, everyone. I'll be back with more stupid (hopefully not AS stupid...) questions.

                      Comment


                      • #12
                        Just be aware that ballast mounting is the most commonly used mounting system for flat roofs. There is nothing mystical about it. Ground mounting is fine too, but codes apply to that as well. Your best option for ground mount is also ballast most likely.

                        It will probably come down to the best way to get the wires where they need to go.
                        Last edited by AzRoute66; 08-23-2017, 01:45 PM.

                        Comment


                        • #13
                          Originally posted by AzRoute66 View Post
                          Just be aware that ballast mounting is the most commonly used mounting system for flat roofs. There is nothing mystical about it. Ground mounting is fine too, but codes apply to that as well.
                          Large loadings of dead weights of a mostly concentrated nature on flat roofs whose original design probably didn't consider such loadings need careful design consideration as do the dynamic loadings they are designed to offset.

                          Comment


                          • #14
                            Originally posted by J.P.M. View Post

                            Large loadings of dead weights of a mostly concentrated nature on flat roofs whose original design probably didn't consider such loadings need careful design consideration as do the dynamic loadings they are designed to offset.
                            The HOA for the building didn't seem to think it would be a problem, but I have a feeling inspectors would disagree with them. It's hard to know for sure since there is a pretty solid-looking support structure underneath, but now that I have all of this in mind, I would rather not risk panels falling through the roof or blowing off into nearby traffic (which includes a lot of huge trucks and pedestrians).

                            Comment


                            • #15
                              Your HOA for the building is probably right. It is TWO panels. If that is a problem, I suggest that folk start looking for new digs sooner rather than later.

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