Finally going to do it right

[tnhomestead]

Ok Going to install my solar system next trip home -- was on the ground, roof, and everywhere else -- looked like Frankenstein meets the Martian Wire Monster! Can anyone tell me if my plans sound OK?

Have 14 different panels(800 watts total), will go on roof, 30 feet max run to combiner box(unfused), panels will be grounded to own copper rod

combiner to trace c-60 3 to 4 foot

to batteries 4 to 5 feet

batteries to cut off switch(190 amp cont, 1000 momentarily) then to 400 amp fuse

then to trace prosign 2000 watt inverter

then to 125 amp panel

generator to 30 amp fused box to input to trace prosine 2000 watt inverter

10. gauge wire from solar panels to combiner
    
6. or 8 gauge from combiner to trace and to batteries
   
2. gauge interconnect for batteries
   
2. /0 to inverter, high grade power wire rated over 400 amps for 10 feet
   
   

any suggestions improvements?

in the bottom of a valley, so limited sun -- which is why I am not going for panel mounts on trackers.

thnx

greg

[Airstream]

With PV arrays on a building each panel or string circuit feeding into the combiner box 'should' be fused inside the combiner box (also serves as a disconnect) and the entire output 'should' be fed through a ground fault interrupter. And all circuits except solid ground wire need to be placed in conduit at least until they enter the structure. Also some serious thought about lightning protection is required...

[electronbaby]

Do you want a code compliant (NEC) install??

If you mount on trackers, (not on the structure itself) you are not required to install a ground fault interrupter. It is a good idea regardless however. Lightning protection is also a good idea, but not required by NEC (yet).

Your battery fuse should be located AT THE BATTERY TERMINAL and sized for 125% of the max inverter current draw based on the inverter nameplate rating. All your wire used must be sized for an ampacity of 25% greater than the max rating of the device you are connecting it to (unless its a dump load- then it must be sized for 50% greater current). You should have a DC or battery disconnect before the inverter (usually fused) for 125% of the inverters rating.

You should have a disconnecting means before and after the charge controller. The charge controller should be fused for 125% of its rated output regardless of PV array sizing.

The wire used on the PV array should be sized appropriately for the short circuit current of the  string it connects. It must then be de-rated for temperature (even if you use 90 C wire). Most common wire used is XLPE/USE 2. It is sunlight resistant. It then must also be de-rated for continuous duty (over 3 hours use). This is the common 1.56  (25% x 25%) multiplier commonly used to size PV equipment.

If you have more than three PV source circuits, you must have a fusible disconnect (each string fused) to avoid any back feeding of any SINGLE string. After ALL these things are met, the wire then must be sized to accommodate less than a 2% voltage drop (usually). You will end up with wiring that will exceed the NEC calculations for current in the end because of the voltage drop issue.

Most commonly available battery cable (usually) does not meet NEC requirements. Its up to you if you want to use it of not. Is your system being inspected? Probably not if its off grid.

All equipment must be bonded. Module frames, rails and tracking equipment. Run bonding wire back to the house with the DC cables. Make the termination inside the 125 Amp service panel. Bring all other bonding wires to this point. Inverter bonding wire, battery negative terminal bonding wire, charge controller ground wire and any other equipment grounding conductor you may have. Then run a grounding conductor to earth from this point. It is up to you if you want to add an extra grounding electrode at the array. Usually if this is done, it is connected to the house grounding electrode with a bare solid conductor buried underground. This eliminated the possibility of your equipment seeing more than one path to earth and eliminated any ground loops you may have.

All of this info can be found in the NEC book and under article 690 (PV systems).

I am by no means an expert. This is just what I have to deal with all the time as I do this professionally.

Hope I didnt scare you.

[tnhomestead]

everything wil be run in conduit -- too many mice in my woods. Will run GCFI on the AC to the house if thats what you meant.  Thnx! Will add a lightning arrestor -- never thought about it. Should be ok on lightning, have a small lightning rod on roof, odds are will hit the trees on the ridge before me -- I hope! LOL Sigh, will look into a fused combiner box, was just thinking of fusing each line. THnx for the help!

[tnhomestead]

I am not scared -- Im always green! WOW No codes where I live, but want it done right -- looks like its gonna cost a lot more than planned, hope I can figure this all out!

THANKS!

still a little green tho!

[scottsAI]

tnhomestead,

May want to reconsider your lightning rod:

Lightning the best I know:

http://www.fieldlines.com/comments/2007/5/8/21473/65854/16#16

Can you put your solar panes above the valley?

Same with lightning rods.

Good luck on your system.

Have fun,

Scott.

[Ungrounded Lightning Rod]

Remember that the wire from the frames/panels to the building ground (along with any bonds among the frames and panels) is a path for lightning currents - like if something nearby gets hit and you get a surge from capacitive coupling to the voltage delta or a sideflash to the panels.

So it needs to be heavy, direct, not make any sharp bends, and not have any loops in it.  (And I wouldn't run it IN a steel conduit but would use the conduit wall itself if the code allows:  Steel conduit is like a ferrite bead for boosting the inductance of a wire running through it.)

Lighting currents start, change, and stop abruptly, which corresponds to EXTREMELY high frequency.  Loops and bends are inductive - more so the tighter the bend and smaller the loop.  Rather than take a sharp bend the lightning will jump OUT of the wire short of the bend and back INTO it just after - if it doesn't find a better route while it's out.  This can create a cloud of vaporized metal where the arc lands on the wire or whatever - igniting things nearby.  Alternatively the lightning/surge arc may land on, run along, or pass through something flammable and ignite it.  So keep the inductance down so the current stays in the wire all the way to the ground.