DIY Panel mounting Ideas-How about galvanized 4" Z purlins?

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Surfpath
Surfpath Solar Expert Posts: 463 ✭✭✭
in PV Installers Forum - NEC, Wiring, Installation #1
I have purchased nine 220w panels to mount on my metal roof...now considering panel mounting ideas.

The roof where I plan to install the panels is above a wide open verandah. The roof is comprised of 3' spaced 2 x 6 hardwood rafters that are steel/concrete embedded in each end followed by a 1" hardwood deck and then several 2" x 3" hardwood battens, and finally an alu-zinc metal roof on top. It's a sturdy roof.

The roof is sort of "seamed." This is not my roof, but you can get an idea...my roof is structurally much sturdier.

Attachment not found.

The skinny is that it's difficult for me to obtain mounting materials, & to import a professional mounting system would be cost prohibitive.

However, I have some spare 4" galvanized Z purlins (20' lengths - like in the photo below) In fact this photo shows some of my roof where the combiner box will probably be mounted.

I was thinking that perhaps these purlins could help. I can also obtain smaller gage (2" x 2" L shaped) slotted angle iron.

How would you suggest securing these panels to my roof?
Ideas appreciated.
-SP
Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
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  • rollandelliott
    rollandelliott Solar Expert Posts: 834 ✭✭
    #2
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    Re: DIY Panel mounting Ideas-How about galvanized 4" Z purlins?

    lag bolts with caulk around them should work fine.
    Im assumingyou are running them horizontally. if so you might want to rise them up a little, not sure how tall they are.
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  • peakbagger
    peakbagger Solar Expert Posts: 341 ✭✭✭
    #3
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    Re: DIY Panel mounting Ideas-How about galvanized 4" Z purlins?

    Make sure you galvanically isolate the solar pansl frames from the galvanized. I ordered some HDPE from McMaster Carr and made big slotted washers to go between the panels and the galvanized struts I used.THe HDPE looks like the stuff milk cartons are made of just thicker. All sortss of consumer products are made with HDPE, so I would just look at the local stores or dump for something made out of HDPe and cut the washers out of it.

    If you are near water especially salt water this is real important. THere is coating on the panel frames that will initially isolate them but it will wear out at some point and once the corrosion starts its hard to stop.
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  • Surfpath
    Surfpath Solar Expert Posts: 463 ✭✭✭
    #4
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    Re: DIY Panel mounting Ideas-How about galvanized 4" Z purlins?
    rollandelliott wrote: »
    lag bolts with caulk around them should work fine.
    Im assumingyou are running them horizontally. if so you might want to rise them up a little, not sure how tall they are.

    Hi Roland,
    You mean lag bolts that would go through the 2x6 rafters underneath and then secure the 4" z purlins to the roof? Sounds good. I just have to make sure it's well caulked [at least the space below is only tiled patio]


    Yes Peakbagger..., galvanic action - can't forget that.
    I like the isolation idea. Would thick neoprene washers do as well?

    I have attached below a drawing of how I envision placing the panels. I am planning to have 3 parallel strings of 3 220w panels in each string. They have Tyco connectors.
    Attachment not found.
    No idea how to wire everything just yet. I would guess the wiring would go from positive to positive (and negative to negative) in each series with the final positive and negative 'ends' of each string going to the combiner box?

    Panel Specs are attached below. Question: I know 150v breakers are required for this off-grid system, but what size breaker amperage is required?
    Attachment not found.

    I was told this would be a simple thing to do.:p:roll:
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
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  • Surfpath
    Surfpath Solar Expert Posts: 463 ✭✭✭
    #5
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    Re: DIY Panel mounting Ideas-How about galvanized 4" Z purlins?

    Or I could go the unistrut way...
    See Video 1 &
    video 2

    I think I can find unistrut. I saw some of the same spring clips in the first video.

    I'd just have to make sure I isolate the panels re. galvanic corrosion, as well as raise the unistrut high enough over the ridges in the metal roof.

    -SP
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
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  • peakbagger
    peakbagger Solar Expert Posts: 341 ✭✭✭
    #6
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    Re: DIY Panel mounting Ideas-How about galvanized 4" Z purlins?

    Neoprene may work but I am not sure how it deals with the potentially high temperature over the long term.
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #7
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    Re: DIY Panel mounting Ideas-How about galvanized 4" Z purlins?

    Hi Surf,

    RE the breaker rating for your PVs, use a 15 A breaker per string. It is the maximum, as stated in the label on your PV modules, but it is the closest standard value above the calculated minimum.

    Have not looked at the videos, yet, but the Channel Nut faces (the spring nut thingies) are spaced about 1/8 inch or more away from the top surface of the open side of the Strut. So, you would need a fairly thick and rigid spacer if you are planning to bolt the PV modules directly into the channel nut with the open side of the strut facing up, toward the PV. Without this thick spacer, the PV frame can easily be distorted by the clamping force of the bolt. This distortion could possibly allow water penetration into the internals of the PV, and COULD easily void any warranty, in my opinion.

    Sorry for my non-metric numbers, I do not think in metrics. Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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  • westbranch
    westbranch Solar Expert Posts: 5,183 ✭✭✭✭
    #8
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    Re: DIY Panel mounting Ideas-How about galvanized 4" Z purlins?

    might these http://www.s-5.com/home/index.cfm, work for you?
     
    KID #51B  4s 140W to 24V 900Ah C&D AGM
    CL#29032 FW 2126/ 2073/ 2133 175A E-Panel WBjr, 3 x 4s 140W to 24V 900Ah C&D AGM 
    Cotek ST1500W 24V Inverter,OmniCharge 3024,
    2 x Cisco WRT54GL i/c DD-WRT Rtr & Bridge,
    Eu3/2/1000i Gens, 1680W & E-Panel/WBjr to come, CL #647 asleep
    West Chilcotin, BC, Canada
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  • Surfpath
    Surfpath Solar Expert Posts: 463 ✭✭✭
    #9
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    Re: DIY Panel mounting Ideas-How about galvanized 4" Z purlins?
    westbranch wrote: »
    might these http://www.s-5.com/home/index.cfm, work for you?

    Innovative clip. I see how it could work for some.

    It seems to require standing seam metal roofing with a thinner "ridge" than my metal roofing. Although there are ridges in my roof, none are thin enough for any fastener to grab a hold of.

    I have found a source of slotted (galvanized???-maybe) steel unistrut. The only challenge would be to isolate the struts from the aluminum framed solar panels and the Aluzinc roof to avoid any galvanic corrosion, as others mentioned below. For the sake of convenience, let's call this product an isolation "washer."

    So, here's the proposed "system"....
     It gets pretty windy at my house location, so something that's fastened onto the roof solidly would be ideal.

    Let me know what you think about this setup-it may help others in a similar situation.
    Thanks!
    SP
    Outback Flexpower 1 (FM80, VFX3048E-230v, Mate, FlexNetDC) 2,730watts of "Grid-type" PV, 370 AmpHrs Trojan RE-B's, Honda 2000 watt genny, 100% off grid.
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #10
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    Re: DIY Panel mounting Ideas-How about galvanized 4" Z purlins?

    Hi Surf..

    Couple of things:

    Be ceratin to space the Strut up off of the roof surface by about an inch or a bit more (from roof surface to the botom of the strut). Otherwise, over time, debris can/will build up under the strut and potentially dam water etc. Additional spacing should help the PVs to run cooler from better air circulation. But, you will need a washer/nut at the roof surface to anchor the bolt adequately. Then another nut/washer at the-under side of the strut.

    Here are some official Strut Washers in several styles, with proper corrision-resistant finishes:
    http://www.cooperindustries.com/content/dam/public/bline/Resources/Library/catalogs/bolted_framing/strut_systems/fittings-flatplatefittings.pdf

    Probably special-order from a whosale electrical supplier. Most of these specialty items are available within 2 days or so, altho things may be a bit different where you are located.

    My 3 cents Good Luck, Vic
    Off Grid - Two systems -- 4 SW+ 5548 Inverters, Surrette 4KS25 1280 AH X2@48V, 11.1 KW STC PV, 4X MidNite Classic 150 w/ WBjrs, Beta KID on S-530s, MX-60s, MN Bkrs/Boxes.  25 KVA Polyphase Kubota diesel,  Honda Eu6500isa,  Eu3000is-es, Eu2000,  Eu1000 gensets.  Thanks Wind-Sun for this great Forum.
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