Announcement

Collapse
No announcement yet.

Reverse tilt kits?

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

  • Reverse tilt kits?

    What solar panel racking vendors provide guidance and support for reverse tilt mounts?
    There are a lot of installers who would like to offer those, but lack the engineering expertise to design them from whole cloth; support from the vendor would help those installers do it right.

    Unirac specifically advises against it with their products:
    http://unirac.com/wp-content/uploads...LICABILITY.PDF

    Spice Solar has one drawing with reverse tilt:
    http://www.spicesolar.com/wp-content...-TILT-ELEV.pdf

    The Australian company Clenergy has the most detailed info I've found so far.
    http://clenergy.com/Products/Mountin...ack/Solar-Roof
    has an adjustable tilt leg installation guide with a table showing base rail support spacing for reverse tilt based on roof slope, wind zone, and building height:
    http://clenergy.com/getmedia/1e86aec..._V3-2.pdf.aspx

    I'd love it if y'all could chime in with info about other vendors that support reverse tilt.
    Last edited by DanKegel; 01-16-2016, 04:21 PM. Reason: Be more specific

  • #2
    Probably.

    Comment


    • #3
      I'll ask IronRidge, standby.
      Solar Queen
      altE Store

      Comment


      • #4
        Dan, looking at the pics in your other thread and I can see why you are concerned.

        It is definitely wind loads you should be concerned about but that is only half the battle. The vibrations created by even low wind speeds will be problematic.

        IMO you should be more concerned with the attachment point.....a lag bolt sunk into the roof rafter is not enough. I'm thinking a more robust attachment mechanism is needed.

        Comment


        • #5
          Wind loading is a real can of worms. The ASTM standards are definitely not done with solar panels in mind. My engineer has software to figure the wind loading and it comes up with stupidly high numbers for the uplift that panels could see (over 150lb per tilted panel on an exposed flat roof). Reverse tilted panels could be way worse. The mounting manufacturers are not going to help you much. Probably going to need to find a local PE to get a building departments approval.
          BSEE, R11, NABCEP, Chevy BoltEV, >2500kW installed

          Comment


          • #6
            Originally posted by solarix View Post
            Wind loading is a real can of worms. The ASTM standards are definitely not done with solar panels in mind. My engineer has software to figure the wind loading and it comes up with stupidly high numbers for the uplift that panels could see (over 150lb per tilted panel on an exposed flat roof). Reverse tilted panels could be way worse. The mounting manufacturers are not going to help you much. Probably going to need to find a local PE to get a building departments approval.
            Wouldn't the permit package already have specified some kind of mounting hardware for the reverse tilt? If as-installed system doesn't match what was submitted on the permit application, there could be some 'splainin to do.
            CS6P-260P/SE3000 - http://tiny.cc/ed5ozx

            Comment


            • #7
              Originally posted by solarix View Post
              Wind loading is a real can of worms. The ASTM standards are definitely not done with solar panels in mind. My engineer has software to figure the wind loading and it comes up with stupidly high numbers for the uplift that panels could see (over 150lb per tilted panel on an exposed flat roof). Reverse tilted panels could be way worse. The mounting manufacturers are not going to help you much. Probably going to need to find a local PE to get a building departments approval.
              The ASTM standards are done with about any structure in mind. Think of tilted lean-to type walls on flat roofs, or shading/rain covers as an example. Depending on the location and zone, and particulars of the orientation, that 150 #/tilted panel ( ~ 17 ft^2 --->>> 150/17 = 8.8lbf/ft^2 --->> wind vel. ~ 60 M.P.H. doesn't sound too high to me. Still, if and unless the person running the software knows what they're doing and can't get the same result by hand to verify, something may be amiss, but probably w/ the input, not the software.GIGO.

              Comment


              • #8
                Originally posted by sensij View Post

                Wouldn't the permit package already have specified some kind of mounting hardware for the reverse tilt? If as-installed system doesn't match what was submitted on the permit application, there could be some 'splainin to do.
                If the structural design calcs are required and if external loadings are required to be considered, bolting/attachment details and strength calcs would normally be included and would show suitability for the anticipated loadings. Sometimes things are not considered. There's code enforcement as it is written and then there's code enforcement as it's sometimes practiced.

                Comment


                • #9
                  We have done a few the engineering is a big factor. Most recent was on a waterfront building on the Chesapeake bay. Exposure category 4 and a bit above 100KW. Can be done but will require a thorough engineering evaluation. In that case roof slope was 10 degrees and panel tilt was 10 degrees. Making the first leed platinum building even more platinum.
                  NABCEP certified Technical Sales Professional

                  [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

                  [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

                  [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

                  Comment


                  • #10
                    IronRidge also does not support them. "[COLOR=#222222][FONT=Helvetica Neue]The reverse tilt applications are often done improperly, and are no longer support by IronRidge. Any failures of reverse tilt installation are not going to be covered by our warranty. This will also hold true with our new tilt legs."[/FONT][/COLOR]
                    Solar Queen
                    altE Store

                    Comment


                    • #11
                      Originally posted by Amy@altE View Post
                      IronRidge also does not support them. "[COLOR=#222222][FONT=Helvetica Neue]The reverse tilt applications are often done improperly, and are no longer support by IronRidge. Any failures of reverse tilt installation are not going to be covered by our warranty. This will also hold true with our new tilt legs."[/FONT][/COLOR]
                      Which may be saying something about the preliminary or other engineering and site planning/prep among other things. The engineering may or may not be complicated, but in any case, necessary, but often missing, and IMO only, often out of willful ignorance. Without doing their thinking for them, Perhaps that's part of what IronRidge is saying between the lines.

                      Part of the reason behind IronRidge's decision may be a consequence of something I've noticed on solar applications and often in R.E. circles. That is, the necessary engineering is often misunderstood, ignored, or not known to exist.

                      While most certainly not painting all R.E. people with the same brush, IMO, it is often easier to find ignorance, poor attitudes and lack of professionalism when dealing with R.E. outfits than say, for example, those found in a refinery or a nuke.

                      I may not necessarily like their products or agree with all their corporate opinions about what's best for the planet, but after an engineering career in/around a lot of conventional energy generation, and a foot and one eyeball in my first and technical passion - R.E - for longer, IMO only, unless I determine otherwise, and sorry to say it, when it comes to professionalism, safety and the quality of the engineering, I'll trust the conventional end of the energy business for those things until I see a change. Some of the ignorance and bad attitudes that are easier to find on a solar job site would not be tolerated if found in, say, a refinery or a large nuke.

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

                      Comment


                      • #12
                        Installing solar panels on a roof is deceptively simple. For flush mounts, the kinks have long been worked out. Reverse tilt, not so much, and fools rush in where angels fear to tread.

                        Australia seems ahead of the US in this regard, judging by the fact that the only vendor willing to specify how to use their mounts for reverse tilt is in Australia.

                        Has there been an article about the issue in any solar industry publication?

                        http://www.solarabcs.org/about/publi...orts/wind-load does not recommend mounting panels at a tilt relative to the roof, but it quite doesn't come out and say "we do not recommend reverse tilt mounts". (I guess it's trying to help people follow good practices, not dissuade them from following unproven practices.)

                        http://www.nabcep.org/wp-content/upl...-7-16-13-W.pdf
                        says:
                        Before recommending or deciding on any PV array mounting system, verify with
                        the mounting system supplier that the hardware is appropriate for the given ap-
                        plication. Also, it is generally not advisable to try to fabricate or copy a mounting
                        system design for smaller projects. This usually costs much more than purchasing a
                        pre-engineered system, and may not meet the structural or environmental require-
                        ments of the application. PV array mounting structures also must be electrically
                        connected to the equipment grounding system, and special bonding jumpers and
                        connectors are available to maintain electrical continuity across separate structural
                        components. Oftentimes, local jurisdictions require engineering documentation to
                        certify the structural integrity of the mounting system and attachments.
                        Which brings us back to the question: do any mounting system suppliers in the US
                        support reverse tilt mount applications?
                        Last edited by DanKegel; 01-21-2016, 01:32 PM.

                        Comment


                        • #13
                          Originally posted by Naptown View Post
                          We have done a few the engineering is a big factor. Most recent was on a waterfront building on the Chesapeake bay. Exposure category 4 and a bit above 100KW. Can be done but will require a thorough engineering evaluation. In that case roof slope was 10 degrees and panel tilt was 10 degrees. Making the first leed platinum building even more platinum.
                          Wow. What LEED version was that building graded against?

                          LEED V2 (2004) was only 52 or more points to meet Platinum requirements. For LEED 2009 and now V4 2015 you need to score 80 or more points to get Platinum.

                          Must be a very energy efficient building.

                          Comment


                          • #14
                            Originally posted by SunEagle View Post

                            Wow. What LEED version was that building graded against?

                            LEED V2 (2004) was only 52 or more points to meet Platinum requirements. For LEED 2009 and now V4 2015 you need to score 80 or more points to get Platinum.

                            Must be a very energy efficient building.
                            Very first LEED Platinum building in U.S.
                            NABCEP certified Technical Sales Professional

                            [URL="http://www.solarpaneltalk.com/showthread.php?5334-Solar-Off-Grid-Battery-Design"]http://www.solarpaneltalk.com/showth...Battery-Design[/URL]

                            [URL]http://www.calculator.net/voltage-drop-calculator.html[/URL] (Voltage drop Calculator among others)

                            [URL="http://www.gaisma.com"]www.gaisma.com[/URL]

                            Comment


                            • #15
                              Originally posted by solarix View Post
                              Wind loading is a real can of worms. The ASTM standards are definitely not done with solar panels in mind. My engineer has software to figure the wind loading and it comes up with stupidly high numbers for the uplift that panels could see [B](over 150lb per tilted panel on an exposed flat roof).[/B] Reverse tilted panels could be way worse. The mounting manufacturers are not going to help you much. Probably going to need to find a local PE to get a building departments approval.
                              Just off the top of my head I do not find that stupidly high. At least not by a full order of magnitude anyway. Think storm winds not ordinary breezes. And then think of the loading per square foot of an airplane wing.
                              SunnyBoy 3000 US, 18 BP Solar 175B panels.

                              Comment

                              Working...
                              X