Portrait vs Landscape layout...does it matter?

HX_Guy
HX_Guy Solar Expert Posts: 296 ✭✭✭✭✭✭
in Solar Beginners Corner #1
I'm getting different things told to me about this, what is your guys' input?

I have one company that says the only right way to do install panels on the roof is in portrait mode and it should be avoid "at all costs" (as he put it) to put the panels in landscape as "that is not good for the roof and it's really not the correct way to do it".

I brought this up with another installer, who suggested landscape because we could fit more panels if needed, and he said it doesn't matter one bit aside from installing in landscape tends to be about 20% more track, therefore more expensive for the installer.

What's your guy's take? Does it matter at all? I don't see why it would.
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #2
    Re: Portrait vs Landscape layout...does it matter?

    If you live in the snow belt, I highly recommend "landscape", as the series cells in the panels run lengthwise. Why does this make a difference? Basically it's because if even one cell in a series string is covered with anything, including snow, that string's output plunges drastically. And as most of today's panels have at least two series strings wired in parallel, if the PV is mounted "portrait" and snow slides to the bottom of the PV, which it normally does, all strings and thus that whole PV is rendered next to useless until the snow is completely gone from it's surface. On the other hand, if it had been mounted "landscape" and the snow slides to the bottom, only half the panel would be out of commission, resulting in you still getting roughly half power instead of none. And that's why when I moved my PV installation to it's present location, I changed them from portrait to landscape. I need my panels to produce electricity, not just look like what some folks may or may not consider pretty. But - - to each his or her own.
    Beyond that, who cares which way they're mounted. It's your house, your money, your decision. Oh, and I'd like someone to explain to me how the roof would know, or care which way the panels are mounted. :D
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,590 admin
    #3
    Re: Portrait vs Landscape layout...does it matter?

    I believe that there is also a preference for the direction of the racking (at least for some/large format panels)... If you mount portrait, you want the racking going horizontal for most support/strength for the panel.

    I am not sure, but I think that the installers prefer horizontal racking across roof rafters. In my humble opinion, horizontal racking probably ties the roof together better.

    For example:

    http://www.solar-electric.com/kyocera-kd320gx-lfb-320-watt-polycrystalline-solar-panel.html/
    Kyocera KD320GX-LFB Multicrystalline Solar Module

    NOTE: This module is designed for use of mounting clamps on the long side of the frame. It is not rated for use of clamps on the short side, which means the module should only be mounted in portrait orientation.

    Also note that (it appears) that this mounting limitation was not specified in either the 2 page glossy or the warranty sheet... NAWS added this to their catalog page for the panel.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • waynefromnscanada
    waynefromnscanada Solar Expert Posts: 3,009 ✭✭✭✭
    #4
    Re: Portrait vs Landscape layout...does it matter?
    BB. wrote: »
    I am not sure, but I think installers prefer horizontal racking across roof rafters. In my humble opinion, horizontal racking probably ties the roof together better.-Bill
    Good point. Mine aren't on a roof, so thinking only of best PV performance that wasn't a concern. With many modern roofs, the area between the rafters isn't all that strong and not best for hardware mounting and mechanical loads.
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #5
    Re: Portrait vs Landscape layout...does it matter?

    Structurally, look at the underside of the roof. Either way can be a problem if the roof isn't up to it. If the mounting struts/rails fall between rafters/trusses and the sheathing isn't heavy enough it will be stressed. This is not s difficult thing to overcome, however.

    Electrically the panels don't care except for how they may be affected by shading/snow cover. The frames themselves can be mounted either way, and are meant to be.

    Your contractor's concerns that landscape mounting should be avoided at all costs is exaggerated. I'd be leery of anyone who made such claims.
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  • HX_Guy
    HX_Guy Solar Expert Posts: 296 ✭✭✭✭✭✭
    #6
    Re: Portrait vs Landscape layout...does it matter?

    I spoke with this company again and here is their claim...

    "Installing panels in landscape mode means you have to run the rails parallel to the trusses which is not good for the roof.
    The correct way to do it is run the rails perpendicular to the trusses which means the panels have to be mounted portrait."

    I asked why can't you mount the rails perpendicular to the trusses and also mount the panels in landscape and they said that voids the warranty from the manufacturer (SunPower in this case) as the rails have to be mounted parallel with the short side (perpendicular to the panel).

    Any truth to this or are these guys full of crap?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #7
    Re: Portrait vs Landscape layout...does it matter?
    HX_Guy wrote: »
    I spoke with this company again and here is their claim...

    "Installing panels in landscape mode means you have to run the rails parallel to the trusses which is not good for the roof.
    The correct way to do it is run the rails perpendicular to the trusses which means the panels have to be mounted portrait."

    Not good for the roof is a vague statement. If the roof is up to the task it doesn't matter how you load it. if it does, the roof is defective.
    I asked why can't you mount the rails perpendicular to the trusses and also mount the panels in landscape and they said that voids the warranty from the manufacturer (SunPower in this case) as the rails have to be mounted parallel with the short side (perpendicular to the panel).

    Any truth to this or are these guys full of crap?

    I can believe the panel company wants the rails perpendicular to the long side even with 'clamp' mounts (as opposed to bolts through the holes in back) because it spreads the 'grip' out over the panel, making them more secure. If they are mounted on the ends there could be considerable flexing over the length of the panel.

    But much of this has to do with exactly what rails and other components are used between the panels and the roof. Quite a number of companies have no problem with landscape mounting so you can't say "it's absolutely wrong in all cases" because that just isn't true.

    Look through our host's section on mounts and you will see they are not all the same: http://www.solar-electric.com/panel-mounts.html
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,590 admin
    #8
    Re: Portrait vs Landscape layout...does it matter?

    Overall, I would be in favor of running rails "across" the rafters--Making for a stronger structure (spreading loads out across multiple rafters.

    And mounting larger panels with short end parallel to the rails--Probably a "stiffer" panel overall (mounting long sides parallel to rails gives you a longer unsupported span--Makes for higher stresses and more flexing).

    So--In general, I would agree with his opinion... Of course, you could mount a second set of rails crosswise to the first--But that would add significantly to the costs of the installation.

    My own roof (~80 year old asphalt shingle roof) has 1/2 the panels in portrait and the other 1/2 in landscape (to fit the available space). And 1/2 the rails run horizontally, other 1/2 vertically (over rafters).

    I am sure my roof would not meet current structural requirements for new construction--However, I do not get snow and wind forces are low--We have tall trees in the area and our damage is most likely from falling limbs (and earthquakes/house fires).

    I knew much less when it was originally installed ~10 years ago (did not really do much in the way of flashing, just L feet and goop by my installer). Could it be better--yea. Have I had any failures due to mounting issues--Not that I am aware of.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • HX_Guy
    HX_Guy Solar Expert Posts: 296 ✭✭✭✭✭✭
    #9
    Re: Portrait vs Landscape layout...does it matter?

    Ok so it doesn't sound like he's just BSing...maybe more just being overly cautious which isn't a bad thing I guess.

    What about the part about the warranty being voided if the panels are installed long side parallel to the railing?
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  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #10
    Re: Portrait vs Landscape layout...does it matter?
    HX_Guy wrote: »
    Ok so it doesn't sound like he's just BSing...maybe more just being overly cautious which isn't a bad thing I guess.

    Probably that he doesn't want to go to the extra trouble and expense to mount landscape. You can do it if you want to put in enough hardware.
    What about the part about the warranty being voided if the panels are installed long side parallel to the railing?

    More likely it has to do with where the fasteners are placed on the panels. If the frames aren't designed for 'end clamping' then it shouldn't be done. Some large panels even have an extra bar placed down their middle for rigidity. If that is there it is supposed to contact the rail for support. If it doesn't there could be too much flexing.

    So there would be extra expense involved in the landscape mounting. How much more panel will it gain you? It could be a very expensive Wattage.
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