Panel "Snow Load" or "Max Load" for RV

brulaz
brulaz Solar Expert Posts: 31 ✭✭
in Caravan, Recreational Vehicle, and Marine Power Systems #1
Comparing several panel brands to put on top of my trailer.

They're all less than 32" wide (which I need). Similar wattage (180-205W), mono-xtalline, have high Vmp (35-37V, so I can run them in parallel to my MPPT).

But two of them have snow or max loads of only <2400pa, while the third (Canadian Solar CS5A-205M) claims more than double that (<5400pa). Oddly one of the <2400pa panels weighs more (16.8kg) than the CS5A (15.25kg).

Seems to me that a higher Max or Snow load implies a more rugged construction, useful in an RV application?

The trouble is, I'm having a hard time finding the Canadian Solar units. One of the others, "Sunny Power SPM195W " is definitely available at <Can$1/watt.

Should I keep looking for a unit with ~5400pa Max/Snow load? I do go over some rugged roads. My trailer has shocks and equalized sprung axles, but still ...

And WOW, panel prices sure have dropped since I last looked 4 years ago. And the wattage per size has increased as well. Very impressive ... definitely makes the whole solar thing more attractive.
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  • brulaz
    brulaz Solar Expert Posts: 31 ✭✭
    #2
    Re: Panel "Snow Load" or "Max Load" for RV

    OK, another panel's brochure says this:
    "New frame technology allows for end mounting under 2400 Pa
    (50 psf) and traditional mounting under 5400 Pa (113 psf)"

    So is the whole diff in how you mount it?

    It would make sense that with a 60" long panel if you mount it only on the end <2400pa would apply, but when supported on the sides, it would be <5400pa.

    So the question becomes can the Sunny Power be mounted on the sides. I'll contact the retailer.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #3
    Re: Panel "Snow Load" or "Max Load" for RV

    I don't know the quality of the various panel vendors out there--I am not in the solar business. So I cannot help you there.

    For small orders (just packing and shipping a few panels) can be expensive--Shipping can be as much as the cost of the panel itself. And panels large than ~140 Watts usually need to ship by truck. Panels larger than ~175 Watts usually need to people to carry/install.

    I notice you live/work in different states and Canada. So, your best bet is to find panels (and batteries) near your home/where they will be installed unless you are ordering them by the pallet and shipping by truck (to a terminal or pay for home delivery). You can find deals on the Internet--But double check (and cross boarder brokerage fees--some folks here drop ship in US boarder towns and then carry the parts across themselves).

    Regarding mounting--You need to follow the specifications. These are like single weight windows (1/8" tempered glass) and the frames, while fairly strong, cannot withstand and bending forces. You need to have a good/stable structure to mount the frames against to meet their rated snow/wind loads.

    One thing to think about in snow climate is how critical is solar production. For off grid folks that need solar power during the winter, they will tilt the panels to ~latitude in the summer (i.e., around 45 degrees for southern Canadian boarder) and tilt them vertical (or near vertical) for winter to encourage snow shedding (and if you have a snow field out front, to capture reflected light).

    On the trailer--If you use it in winter/summer and North/South--You may have to really think about tilt and a strong structure (withstand wind while on the road).

    I believe the landscape/portrait mounting can work--You just need to make the structure underneath with "up down"/"left right" racking based on your and the panels' needs.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • brulaz
    brulaz Solar Expert Posts: 31 ✭✭
    #4
    Re: Panel "Snow Load" or "Max Load" for RV

    Yes, I'm trying to get them locally to save shipping. So far only the Sunny Power seem to be available for local pickup. And I just want two panels, not palettes.:D

    You mentioned "their rated snow/wind load". And I guess I've been comparing apples and oranges. Wind and snow ratings are different. The Sunny Power retailer just told me that the <2400pa rating they report is for wind load only, it is <5400pa for snow. The Canadian Solar panel claim <5400pa for snow load, but doesn't report wind load. And then there's what I quoted earlier for the Kyocera.

    I'm getting the impression that all the recent 30" x 60" Mono Xtalline panels in the 180-205W range are structurally similar and rated <2400pa for wind load and <5400pa for snow. And as their electrical differences are small, I'm left with availability and cost. So right now it's the Sunny Power SPM 195W.

    The other RV installations I've looked at have all successfully used just 4 panel attachment points, along the 60" sides, not the 32" ends. So I'll go with that. I am more worried about the strength of attachment to the RV roof (wood screws and glue), than the attachment to the panel (SS bolts).

    EDIT: And I hope this trailer only rarely sees snow. We're "Snow Birds" and head South at the first sight of the white stuff.

    Many thanks.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #5
    Re: Panel "Snow Load" or "Max Load" for RV

    Many RV installations just bolt a hinge or Z bracket to the panel, and mount the other side to the RV (obviously sealing/finding structure underneath). The aluminum frames on the solar panels are not really designed for this type of mounting that can "twist or warp" the frames.

    Ideally, you would make your racking (steel/aluminum) and hinge/mount that to the RV roof (racking that will not twist or rack). Then clamp the solar panels+frames to the underlying racking.

    What to most RV'ers do? I don't know, but I would suspect a lot of #1. As the panels get physically larger, having a solid rack to mount the panel frames to is probably getting more important--But #2 is probably overkill for most people.

    10 years ago, a 100 watt panel cost $1,000 or more... today a 200 Watt panel costs ~$200--the "risk" of failure is much less.

    They will probably work just fine if the mounting to the roof is firm. Just today, saw a smaller RV trailer with a ~130 watt panel setup up like "wing" (on a race car) on the rear roof of the trailer. Nothing fancy. Just some sort of hinge/brackets at the front roof, and two spindly legs to hold the panel at ~45 degrees off the roof. Worked for him.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • brulaz
    brulaz Solar Expert Posts: 31 ✭✭
    #6
    Re: Panel "Snow Load" or "Max Load" for RV
    BB. wrote: »
    Many RV installations just bolt a hinge or Z bracket to the panel, and mount the other side to the RV (obviously sealing/finding structure underneath). The aluminum frames on the solar panels are not really designed for this type of mounting that can "twist or warp" the frames.

    Ideally, you would make your racking (steel/aluminum) and hinge/mount that to the RV roof (racking that will not twist or rack). Then clamp the solar panels+frames to the underlying racking.

    What to most RV'ers do? I don't know, but I would suspect a lot of #1. As the panels get physically larger, having a solid rack to mount the panel frames to is probably getting more important--But #2 is probably overkill for most people.
    ...

    Over on the RV forums I've seen both. Think they sell the Z brackets here, but I don't like them for the "twist or warp" reasons you mentioned. Especially since my roof is not flat. You could use two Z's without putting stress on the frames, but almost certainly the next two would twist it somehow.

    One of the best "simple" solutions I've found at another site is to make your own Z brackets out of two pieces of right angle Al held together with a single bolt. The first two constructed Z's could be drilled and bolted loosely together and put in place. With the other two you would adjust the bolt placement so no stress was put on the frame. A little hard to describe:Attachment not found.
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  • Iceni John
    Iceni John Solar Expert Posts: 103 ✭✭
    #7
    Re: Panel "Snow Load" or "Max Load" for RV

    I've just finished making a walkway on the roof of my bus that my eight Sharp 255W panels will be hinged to, and this will allow them to lay from 20 degrees below horizontal (against the curved roof) up to 50 degrees high (to capture winter sun). Each panel will sit inside its own support frame made from a continuous 16' length of 1.75" x 1.75" x 1/8" 6063 angle (with a 2' length of angle to complete the needed 17.5' overall length!). This way the panels will be isolated from any flexing caused by wind loads or driving - I'll attach them to the frames by their four 5/16" holes under the long sides, with resilient spacers to prevent the panels themselves twisting or distorting.

    It's a lot of work to do it this way, but I want to be sure that sudden gusts of wind in the desert won't cause any problems even if the panels are fully raised, and that driving at 60 MPH won't hurt them either.

    John

    40' Crown bus with 2kW of tiltable panels on the roof:

    Eight Sharp 255W, two Morningstar TS-MPPT-60, Magnum MS2000, Champion C46540 generator converted to propane, eight golfcart batteries, and maybe a small Exeltech inverter for the fridger.

    Southern California

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  • scrubjaysnest
    scrubjaysnest Solar Expert Posts: 175 ✭✭✭
    #8
    Re: Panel "Snow Load" or "Max Load" for RV

    Good to see you getting serious about solar Bruce. I've been kicking around the idea of using aluminum angle the long way to strengthen the panels. Also use sliding brackets like on the window stone guards as a tilt system. I can't say I have ever heard of wind loading being a problem going down the highway; except for A/C covers.

    ken
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  • brulaz
    brulaz Solar Expert Posts: 31 ✭✭
    #9
    Re: Panel "Snow Load" or "Max Load" for RV

    Hi Scrubjay,

    The 2x195W panel install went well using the Al angles as in the picture. Used 3M4200 Adhesive Sealant and SS screws, and so far the panels have stayed on!
    I kept it simple without any tilt mechanism.

    Last summer we used them a lot at several non-electric Northern Ontario Parks, but the days were a lot longer and it was easy to find non-shady spots. In fact the Ontario Parks reservation system allows you to select for shady or non-shady sites.

    We're down in your territory now, avoiding the storms up north.
    Coming down, we actually found a fairly sunny spot in the Great Smoky Mountain N.P. (Smokemount campground) so the batteries didn't lose a lot of juice over our 2 day stay there.
    But probably will not be using the Panels much again in Florida as the Everglades N.P. now has electricity.
    But when we return in the spring (before leaf out) we plan to stay longer in Great Smoky N.P..

    Cheers
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