how many mounting rails behind each panel?

Individual panel dimension is 58x26", 30lbs each.

My plan is vertical pairing along the long edge, resulting in three 58x52" pairs, which will be placed in a horizontal line on my roof.

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The panel frames have 4 pairs of mounting holes on each long edge, at 6" and 16" from each end.

I'm using 2 x 2 x .1875" aluminum angle for vertical rails to create each pair.

How many rails per pair do I need? Two seems like plenty, but what do I know? Are you guys using four rails per pair?

If two, which holes? The inner two pairs or the outer two pairs?

Thx!

Comments

  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: how many mounting rails behind each panel?
    DSinOR wrote: »
    Individual panel dimension is 58x26", 30lbs each.

    My plan is vertical pairing along the long edge, resulting in three 58x52" pairs, which will be placed in a horizontal line on my roof.

    [ ] [ ] [ ]
    [ ] [ ] [ ]

    The panel frames have 4 pairs of mounting holes on each long edge, at 6" and 16" from each end.

    I'm using 2 x 2 x .1875" aluminum angle for vertical rails to create each pair.

    How many rails per pair do I need? Two seems like plenty, but what do I know? Are you guys using four rails per pair?

    If two, which holes? The inner two pairs or the outer two pairs?

    Thx!

    What wind zone are you in? How much snow load do you get? What roof zone are the modules mounted in?

    For most situations two rails per module (four attachment points) is sufficient, but in high stress locations more may be needed.
  • Organic FarmerOrganic Farmer Solar Expert Posts: 128 ✭✭
    Re: how many mounting rails behind each panel?

    I read the manual for my panels. If you mount supports lengthwise [on the 58" side] then you only need two for an individual panel.

    Placing two panels side-by-side and mounting to 58" supports you need 3 supports. One being shared by both panels, and two on the outside.

    Three panels side-by-side would need 4 supports.

    From my panel's manual. if you mounted 26" supports running the short way across each panel, then it gets into a lot of other measurements and gibberish about stress and snowload. They are sweating that the panels would fold unless the supports are spaced at exactly the right places. From briefly scanning through the pages, what stood out to me is that running supports lengthwise is best.
  • westbranchwestbranch Solar Expert Posts: 5,183 ✭✭✭✭
    Re: how many mounting rails behind each panel?

    ??? running the supports perpendicular to the long side would give more support to the panel. doing the other direction would leave the long side with NO support for the max length per panel except at each end..??? :confused::confused: the latter to me is a recipe for failure.:cry:
     
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  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: how many mounting rails behind each panel?

    What angle will the panels be mounted at? The steeper the angle should mean the less support needed. I am mounting some 68" x 36" panels on a roof with 12/12 pitch (45 degrees). I plan to use just 2 rails supporting each panel - centered and running perpendicular to the long axis. Snow and wind are a significant factor for my situation.

    You can look at the Iron Ridge or Unirac web sites and use their configuration tools to get recomended mounting rail configurations with the associated engineering.
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: how many mounting rails behind each panel?
    westbranch wrote: »
    ??? running the supports perpendicular to the long side would give more support to the panel. doing the other direction would leave the long side with NO support for the max length per panel except at each end..??? :confused::confused: the latter to me is a recipe for failure.:cry:
    I don't think you understood what he was saying. Either that, or I didn't. :D

    What I got was that he recommends running a pair of rails underneath the long sides of each module frame the whole of its length and bolting to the rail through the holes in the frame, sort of like stretcher poles.
  • Organic FarmerOrganic Farmer Solar Expert Posts: 128 ✭✭
    Re: how many mounting rails behind each panel?

    Hmm, my panels are 68" X 37 1/2". Pre-drilled mounting holes are along the long side, the 68" sides.

    From reading the manual, two supports running the entire length of the long sides, 68" [or longer] seems to be more supportive; then supports mounted perpendicular [or the 37 1/2" length].

    When doing 37 1/2" short-side supports, then far more attention must be paid to placement and stresses.
  • mtdocmtdoc Solar Expert Posts: 600 ✭✭
    Re: how many mounting rails behind each panel?

    Is it a roof, ground or pole mount? For flush roof mounts I believe the mounting holes on the panel are usually not used. Panels are tied to rails with clamps between panels and on outer edges of the outside panels. At least that is my understanding and is how the Iron Ridge and Unirac systems are designed. It would be hard to access the underside of mounting holes on panels flush mounted to a roof. Others here will have had more experience with this I'm sure. Tilted roof mounts, Ground mounts or pole mounts allow more options.
  • ggunnggunn Solar Expert Posts: 1,973 ✭✭✭
    Re: how many mounting rails behind each panel?
    mtdoc wrote: »
    Is it a roof, ground or pole mount? For flush roof mounts I believe the mounting holes on the panel are usually not used. Panels are tied to rails with clamps between panels and on outer edges of the outside panels. At least that is my understanding and is how the Iron Ridge and Unirac systems are designed. It would be hard to access the underside of mounting holes on panels flush mounted to a roof. Others here will have had more experience with this I'm sure. Tilted roof mounts, Ground mounts or pole mounts allow more options.
    For sure, systems of any size to them would be a huge pain to install using the mounting holes; virtually all rooftop flush or parallel systems are mounted on rails running perpendicular to the long axis of the modules secured by end and mid clips attached from the front side.
  • Jim45DJim45D Solar Expert Posts: 102 ✭✭
    Re: how many mounting rails behind each panel?

    Apparently the fellow that started this thread isn't answering. Yesterday he sent me a PM, and gave his e-mail address. I contacted him within a hour of receiving his message. He hasn't replied back. He wanted to see photos of how I had mine mounted, and also to me he was talking about a RV installation. He did mention that.

    Jim
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