panel placement on roof

blue
blue Registered Users Posts: 35 ✭✭
in PV Installers Forum - NEC, Wiring, Installation #1
Is it better to place the panels towards the ridge or near the bottom of the roof?
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  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    #2
    Higher elevation is cleaner - less road dust .  You don't want them to be a sail and catch wind off the back of the roof.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,637 admin
    #3
    Depending on where you live, you may end up with limitations based on the new NEC (national electric code) that has setbacks/walkways for firefighters to access the roof and panels (i.e., cut holes in roof to ventilate smoke and heat).

    I think you are in Florida--So you don't have problems with snow (both clearing snow and shedding snow).

    You are going to have standards to bolt down the roof/rafters/arrays to meet the hurricane codes which may have some limitations/retrofit issues too.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • MrM1
    MrM1 Registered Users Posts: 487 ✭✭✭✭
    edited October 2018 #4
    Except for potential offsets from eves and roof lines,  I think more toward the top is better (for several reasons) and possibly safer.  If you slip toward the top,  more opportunity to get stopped before you go off the edge.    I was painting an upper wall over one section of roof  while standing on the crack head roofers roof jacks once.  He had a compressor,  shingles, himself and me on it.  "sure it's fine ..." until it gave way and we all starting sliding.  Compressor and shingles never stopped.  Thankfully we were up hi enough that we did.  Customer was none the wiser :hushed:
    REC TwinPeak 2 285W 3S-3P 2.6kW-STC / 1.9kW-NMOT Array / MN Solar Classic 150 / 2017 Conext SW 4024 Inverter latest firmware / OB PSX-240 Autotransfomer for load balancing / Trojan L16H-AC 435Ah bank 4S connected to Inverter with 7' of 4/0 cable / 24 volt system / Grid-Assist or Backup Solar Generator System Powering 3200Whs Daily / System went Online Oct 2017 / System, Pics and Discussion
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  • blue
    blue Registered Users Posts: 35 ✭✭
    #5
    Thanks, I was thinking about stress on rafters. Never thought about dust or saving a fall. 
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  • 706jim
    706jim Solar Expert Posts: 523 ✭✭✭✭
    #6
    Well here's another take: I placed my panels as high up towards the peak as possible, with 7 ancient Arcos in one row and 4 Astropowers below the Arcos. The result was that there was nearly 8 feet of glass that shed rainwater like a waterfall. Consequently, the last 4 feet of shingles had to resist this cascade of liquid and prematurely started to leak.
    So when I replaced the shingles this summer, the panels went onto the ground.
    Island cottage solar system with appriximately 2500 watts of panels, 1kw facing southeast 1.3kw facing southwest 170watt ancient Arco's facing due south. All panels in parallel for a 24 volt system. Trace DR1524 MSW inverter which has performed flawlessly since 1994. Outback Flexmax 80 MPPT charge controller four 467A-h AGM batteries. Insignia 11.5 cubic foot electric fridge 1/4hp GSW piston pump. My 31st year.
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  • dennis461
    dennis461 Registered Users Posts: 109 ✭✭✭
    #7
    blue said:
    Is it better to place the panels towards the ridge or near the bottom of the roof?
    Center.
    When you do wind loading calculations, the wind force lifting panels is greater at the four edges of the roof.  All other factors will most likely be the same, tilt, azimuth, shading, snow load.
    Camden County, NJ, USA
    19 SW285 panels
    SE5000 inverter
    grid tied
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