Unsure of bonding flexible solar panels on asphalt roof

adam
adam Registered Users Posts: 1 ✭
in PV Installers Forum - NEC, Wiring, Installation #1
Ok long story short.  I have 8 sun power (windy nation) 100w panels flexible w fiberglass or plastic 1/8 thick backing.  they have no frames.  im connecting off grid but on a roof asphalt shingles. using morningstar mppt 60 and their gfpd unit, a disconnect/ combiner midnite mpnv6 w some big agms in parallel 12v probably.  i havent got inverter yet prob 2000 w continuous  at 12v or 24 nor figured my max battery config yet i figure 12v safer.  maxing voltage out w panels prob to charger at 12v should i do 24?,  mppt says 800 watt max at 12v in so prob do that however i may do 2 strings of 400 at 24v input to charger for better sun insurance case 1 panel fails i got 4 others unaffected instead. im unsure yet.  my big question is do i need to bond anything on panels since there is no frame? everything else will be earth bonded to grounding rod. do i need to make metal frame, should i then bond frame to system? what should i do because i need to use these panels and im scared of the current w no earth bond in case of strike or should my  panels come loose in a storm or get struck.i feel i may have some extra ground protection w gfpd 150v unit i have to use.  some good info would be appreciated.  this system will power a 20k saltwater reef off grid but in house without ac tied. separate for me is best and i have intentions of using panels on big boat someday.   
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  • Photowhit
    Photowhit Solar Expert Posts: 6,003 ✭✭✭✭✭
    #2
    Not sure what your load is... Likely too small a system or at least marginal for a fridge.

    The panels would likely 'like' to be off the surface of the roof. If they are designed to be frameless and have mounting holes/grommets. I'd use those. Personally don't like roof mounts, but if you do, you might mount some 2x4's off the surface of the roof on piers and mount the panels to them. If they stay cooler they will produce better.

    24 volt would be my choice if you think you might want/need a larger system. You will likely need 2 strings even for a 12 volt system, the VOC is likely 20+ volts so a string of 8 would be 160 volts +. MPPT type charge controller usually work most effiecently at about double the output voltage, the output voltage will be around 15 volts for a 12 volt system and 30 volts for a 24 volt system.

    You likely won't/can't ground your panels. There is no frame or electrically conductive material to ground. 

    Home system 4000 watt (Evergreen) array standing, with 2 Midnite Classic Lites,  Midnite E-panel, Magnum MS4024, Prosine 1800(now backup) and Exeltech 1100(former backup...lol), 660 ah 24v Forklift battery(now 10 years old). Off grid for 20 years (if I include 8 months on a bicycle).
    - Assorted other systems, pieces and to many panels in the closet to not do more projects.
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