Hooking everything up

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nch18
nch18 Registered Users Posts: 11 ✭
in Solar Beginners Corner #1
Hey everyone, I now have the basics for my system and have spent several days trying to figure out how it all gets connected together. I have a friend in the business who has generously offered to help wire it all up but I need to come up with the plan and list of materials first.

Basically, I'd like to order everything I'm going to need that can't be bought locally at HD/Lowes/Harware store/Electrical Supply etc. I'd be very grateful if people could look at my shopping list and suggest any additional items I'm overlooking since this is my first time at this.

Basic System:
(6) 215W Evergreen Panels arranged into two strings of three panels.
(1) Midnite Solar Classic 150 Lite Charge Controller
(4) 12v AGM Batteries wired to 300AH @ 24v (undersized but will upgrade in the next year or two)
(1) Xantrax Prosine 1800 24v Inverter

What I have for wire and overcurrent protection:
Array to Combiner Box: #10 MC4 cables to two 150VDC 15A breakers in combiner box.
Combiner to Controller (88'): #10 tray cable with one 150VDC 30A breaker before conroller.
Controller to Batteries (5'): #2 with 48VDC 100A breaker
Battery Interconnects (1-2'): #2
Battery to Inverter (5'): #2 with 48VDC 150A breaker


So I'd like to just sketch out my thinking on how this will all work...

Each string of panels will max output 12.69A Isc and 126Voc (with 1.56 safety factor included, Isc is 8.12)

I'll take the 4 wires from my two strings of panels, cut a couple of MC4 connectors in half, and use the resulting pieces to bring the 4 wires into a combiner box such as this http://www.solar-electric.com/mnpv3.html. I can run each of the two positive wires through a 150VDC 15A breaker. With the two strings now combined, I'll be outputting max power of 26A Isc and 126Voc.

I'll run #10 2 conductor tray cable the 88' from the combiner box to the equipment cabinet that houses my batteries, charge controller, and inverter. It will then go through a 150VDC 30A breaker before going to the charge controller.

After the charge controller, I'll be running #2 welding wire to the battery bank. This will run through a 150VDC 100A breaker.

The battery bank will be connected via #2 welding wire as well. Do I need fuses at the battery if I have a breaker on each side?

The battery bank will connect to the inverter via #2 welding wire and go through a 150VDC 150A breaker. Is this undersized? The inverter surges around 3000W so at 24V that's around 125A max rough math.

Well that's my basic plan, thanks for reading. Does that seem reasonable? I don't know anything about grounding yet but I do have some grounding rods. Can I buy the wire and other materials for that locally? Do I need to think about a lightning arrestor or can that be added down the road a bit. Anything else, do I need grounding lugs for my solar panels? They seem crazy expensive, can I just rig something up with local materials?


Thanks!!

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  • ywhic
    ywhic Solar Expert Posts: 621 ✭✭
    #2
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    Re: Hooking everything up

    The max wire size for the Midnite is 4 AWG wire, not 2.. AWG 4 will handle (is rated for) the max of 96 amps from the controller... and yes a 100 amp breaker would be correct going DOWN to the battery bank..

    15 amp breakers for each string is fine.. I would suggest using a 60 amp breaker before the controller and not a 30 as you may decide to grow your system.. (and you got the 15's on the combiner anyway).. 60 is just about the max amps into the Midnite 150 anyway prior to MPPT conversion from the numbers I juggled with when testing things on there Calc page..

    Others will be along to also add in tips/suggestions..
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  • nch18
    nch18 Registered Users Posts: 11 ✭
    #3
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    Re: Hooking everything up

    Awesome thanks ywhic. I went from #4 to #2 from the CC to save money on the 10' minimum order from NAWS, thought I could just use #2 for everything, oops. Good catch.

    The 60A at the controller is a good call too, the overcurrent isn't as important since I have the 15's, just wanted a way to cut power.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #4
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    Re: Hooking everything up

    you can still use the larger #2 wire and just go with a small #4 pigtail from either a small distribution block like this,
    http://www.solar-electric.com/16220-2.html
    or go with a bus bar connection like this,
    http://www.solar-electric.com/tbb.html

    the bus bars are cheaper.
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  • nch18
    nch18 Registered Users Posts: 11 ✭
    #5
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    Re: Hooking everything up

    Thanks neil. I guess I'll just go with #4 though, I'll only need to order like 2-3 extra feet, so by the time I order a bus bar it's really 6 of one half dozen of the other.

    I assume since no one's jumped in waving their arms I'm not too far off and can go ahead and order things. Thanks again guys.
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  • Vic
    Vic Solar Expert Posts: 3,208 ✭✭✭✭
    #6
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    Re: Hooking everything up

    Hi nch18,

    Allowing for expansion is often a good idea, however going to a 60 A input breaker for the CC is, in my opinion, too large to protect the #10 AWG TC. 30 Amps would be the max, but have not looked at the TC specs.

    You could make the transition from #2 Ga to #4 Ga wire on the CC output side at the battery end of the breaker, without any other giblets. #4 is a bit of a stretch Ampacity-wise. If this system will be inspected, this could fail. A very short run of #4 Awg might pass from the CC to breaker.

    I am not a Code Guru, howevcer. 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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  • nch18
    nch18 Registered Users Posts: 11 ✭
    #7
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    Re: Hooking everything up

    Thanks Vic. The 60A breaker is just being used as a switch really because there's already 30A overcurrent protection for the #10 up at the combiner box.

    Like you're idea of just using the #4 only from the CC to breaker and #2 down to the batteries. I'm sure #4 all the way would be fine as Midnite specs it that way but I'd prefer #2 for the longer stretch.
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