Portrait vs Landscape layout...does it matter?

[Volusiano]

I think the bottom line is that in most cases, the overriding reason to do portrait is that it'll take less railing in portrait mode and therefore lower cost. That's why portrait layout is more popular than landscape layout. And this is dictated by the direction of the trusses. Had the trussed been going horizontal on the roof for some reason, I would bet that the landscape layout would become more popular. It's all about the $.

[russ]

Totally agreed - Too many sales people have no idea at all but love to chatter.

Assuming for the moment a rectangular layout, and at least 4 attachment points between each panel and the rail system, with one panel "touching" two rails, I think the company is mistaken due to what seems to be their resulting implication that the rails must be perpendicular to the short side of the panel. Snow loads will be the same no matter the orientation between panel and rails. For most applications were the plane of the array is parallel to the roof, wind loads will probably be similar or very close in either orientation, maybe even a bit less for landscape vs. portrait if the array is not parallel to the roof, tilted or sawtooth. I agree it is usually and probably almost always far better design, depending on the layout and mounting surface to have the rails normal to the trusses in a roof system to spread the load among as many trusses as possible and not just a few. This however, has little to do with the orientation of the instrument of the induced loads, i.e., the panels.

My observation is that most arrays use portrait for the panels but the overall array is usually landscape. Looking at the roof loading, it may or may not be necessary to adjust the array layout with respect to orientation or shape as conditions warrant and/or as the designer decides, but I doubt this has little to do with the orientation of the rails with respect to the individual panel orientation - long or short side. There MAY be some advantage to being able to control the max. dimension between clips in portrait, but in the end that has the tradeoff of possible increase in individual panel bending moment and "using" fewer trusses for the same # of panels. There ain't no free lunch and each design is different.

I designed my array before I got any bids, including structural w/wind & seismic per UBC/ASCE etc. The chosen vendor got very close to my racking layout without knowing it. My array is 4 X 4 landscape with 8 rails perpendicular to the trusses, each panel supported by 2 rails.

I looked at the racking websites this A.M. Maybe I missed something but I can' find any reference to landscape vs. portrait with respect to panel orientation in any of their design info or literature.

[J.P.M.]

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?

Assuming for the moment a rectangular layout, and at least 4 attachment points between each panel and the rail system, with one panel "touching" two rails, I think the company is mistaken due to what seems to be their resulting implication that the rails must be perpendicular to the short side of the panel. Snow loads will be the same no matter the orientation between panel and rails. For most applications were the plane of the array is parallel to the roof, wind loads will probably be similar or very close in either orientation, maybe even a bit less for landscape vs. portrait if the array is not parallel to the roof, tilted or sawtooth. I agree it is usually and probably almost always far better design, depending on the layout and mounting surface to have the rails normal to the trusses in a roof system to spread the load among as many trusses as possible and not just a few. This however, has little to do with the orientation of the instrument of the induced loads, i.e., the panels.

My observation is that most arrays use portrait for the panels but the overall array is usually landscape. Looking at the roof loading, it may or may not be necessary to adjust the array layout with respect to orientation or shape as conditions warrant and/or as the designer decides, but I doubt this has little to do with the orientation of the rails with respect to the individual panel orientation - long or short side. There MAY be some advantage to being able to control the max. dimension between clips in portrait, but in the end that has the tradeoff of possible increase in individual panel bending moment and "using" fewer trusses for the same # of panels. There ain't no free lunch and each design is different.

I designed my array before I got any bids, including structural w/wind & seismic per UBC/ASCE etc. The chosen vendor got very close to my racking layout without knowing it. My array is 4 X 4 landscape with 8 rails perpendicular to the trusses, each panel supported by 2 rails.

I looked at the racking websites this A.M. Maybe I missed something but I can' find any reference to landscape vs. portrait with respect to panel orientation in any of their design info or literature.

[Volusiano]

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?

Actually what they said makes a lot of sense to me.

The first part that makes sense is that if you have the rail perpendicular to the trusses, you can control the exact spacing of the rails from each other. If you run the rails parallel to the trusses, your rails must be right on the trusses or else there's no mounting point, and this doesn't allow flexibility on where the spacing between the rails can be. The only way to solve this is to have 2 layers of rails. The bottom layer of rails is perpendicular to the trusses, and the top layer of rail can sit on the bottom rails and be parallel to the trusses and still be placed for correct spacing. This will of course cost more money, not to mention having the panels placed a bit higher than normal. And this is assuming that somebody offers a rail layer on top of another rail layer solution.

The bit about needing to have the rails parallel to the short side of the panel may make sense if the panel is designed to be clamped on the long side only and the short side is not designed with clamping in mind.

If either side can be clamped just the same as long as 4 clamping points are required, then it would take a lot more rails if they run parallel to the long side -> more $.

Overall, I can see a lot of good logics in favor of mounting the panels in portrait mode.

[HX_Guy]

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?

[russ]

Quote from your post, "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"."

The entire panel has to be clear of snow - yes

[Mb190e]

I wasn't necessarily told it was wrong but i was told, if you put them in portrait layout it spreads the weight of the panels out over more of the roof rafters. And if you get snow the panel will start working quicker in landscape layout. I was told that it starts working after the first third of the panel is uncovered in landscape and portrait the whole panel has to be uncovered.

[russ]

No difference - the installer telling you one way is bad has shown himself to be a fool!

[HX_Guy]

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.