10kw system purchased... now to put it together.

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jovial_cynic
jovial_cynic Registered Users Posts: 2 ✭
edited April 2016 in PV Installers Forum - NEC, Wiring, Installation #1
New guy here.  First post.

I'm normally a DIY kind of guy, but I might be in over my head  just a little bit. Hopefully I can get some direction other than "just hire somebody."

For a quick rundown, this is what I have:

28 x 300w 36v 8.3amp solar panels
10kw SMA Sunnyboy inverter
A field (ground mount location)
About 280 ft of distance between my panels and the main panel to the house.


I've already put together a rack and it's ready to put the panels up, but I need to start digging trenches and laying wire. 

I've read some debates on running the long length either AC or DC (run whatever is higher voltage the longest length), which means running at least one pair of thick wires for the DC run of 280 feet.  The SMA inverter has 4 channels... so does that mean I could run 4 pairs (7 panels each) if I wanted to? The advantage would be smaller wires, but the disadvantage would be having to have 4 sets of smaller wire, right?

Any thoughts or suggestions or questions I should be asking/answering before going forward?
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    edited April 2016 #2
    Hi jovial_cynic,
    I don't have a grid tie inverter but wiring 4 strings of 7 panels sounds right from what I've read. Check your manual to make sure. I wouldn't use anything smaller than 6 AWG wiring for the 280 foot run as that would keep voltage loses less than 1% per string. However it is really up to you. As you know larger wire cost more. Here is a voltage drop calculator  to check different wire sizes and loses in voltage. String voltage is 252 volts DC at 8.3 amps.
    http://www.calculator.net/voltage-drop-calculator.html
    Good luck,
    Rick
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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  • jovial_cynic
    jovial_cynic Registered Users Posts: 2 ✭
    #3
    I've done some more research.  My inverter needs quite a bit more than 7 panels to meet the minimum voltage; the inverter is quite picky. I'll have to have either 11 or 12  panels in a single string to get the voltage high enough to meet the requirement.

    Additionally, having a combiner box near the panels means I won't have to run multiple sets of wires to the inverter - once the wires are combined at the combiner box, I can run a single pair of wires. 
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  • Raj174
    Raj174 Solar Expert Posts: 795 ✭✭✭✭
    #4
    Great news, that makes it easier and saves money.
    4480W PV, MNE175DR-TR, MN Classic 150, Outback Radian GS4048A, Mate3, 51.2V 360AH nominal LiFePO4, Kohler Pro 5.2E genset.
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