Running wire from solar panels to equipment 100 feet away

wiseacre

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Solar panels:
Rated Power: 195W
Open Circuit Voltage (Voc): 21.6V
Short Circuit Current (Isc): 10.83A
Working Current (Iop): 9.02A
Output Tolerance: ±3%

I have 6 (plan for more) and will wire 3 pairs in series - 1+1, 1+1, 1+1 - for a 24 v system

I would run them to a combiner box (over sized for upgrades/additional panels)
This is where I get confused.
I need to run wire from the panels about 100 feet to the house.
What would the output of the combiner box be with my 3 strings?
What would the wire size need to be from the combiner box.

Now I probably could make it simple and run wires from each string and put the combiner box at the house. Lots and lots of wire (WindyNation sells 10 AWG panel wire up to 150 feet) so this seems like a possible but expensive option.

What gets me is when I calculate wire size from the combiner box (100 feet away) I get a size too large to fit any of the components. Either I'm right or more likely I'm using the wrong figures. That's why I thought of using long wires from the panels to the house but even then, just because someone makes such long cables doesn't mean the voltage drop is acceptable. I just don't know.
 

circus

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If you run three in each series you could save some on the wire. Depends on your controller. I'm limited to 150 volts or below on the controller I own. Plenty for all to be in series, then puny wire would work.
 
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wiseacre

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panels are 2s3p
been suggested that 3s2p seems possible for my controller (24V System best mppt working voltage range (36V-72V)
panel.

Solar panel
Rated Power: 195W
Open Circuit Voltage (Voc): 21.6V
Short Circuit Current (Isc): 10.83A
Working Current (Iop): 9.02A
 

iamrich

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Dec 17, 2020
Messages
941
Location
Elgin, Texas
Rated Power: 195W
Open Circuit Voltage (Voc): 21.6V
Short Circuit Current (Isc): 10.83A
I am not sure I would even use a combiner box in this case. I would just combine with a branch connector and use 10awg in conduit, or run 2 sets of 12awg in a conduit from the panels to the controller and use a MC4 branch connector at the controller. Put a couple of 15amp fuses inline. You are pushing ~66v at ~22a max so 10awg should do it. You are a little close to max voltage, so use the 100-150ft voltage drop to your advantage.

 

rhino

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What gets me is when I calculate wire size from the combiner box (100 feet away) I get a size too large to fit any of the components. Either I'm right or more likely I'm using the wrong figures. That's why I thought of using long wires from the panels to the house but even then, just because someone makes such long cables doesn't mean the voltage drop is acceptable. I just don't know.
That is why for longer distances you want to configure your panels to have much higher voltage and a charge controller that can handle it. Using a 150V max Voc controller would allow you to put 5 or 6 in series (depending on how cold it gets by you) and reduce the cable size you need even if using aluminum. If you had 2 sets of 5 in series and a controller that can handle 150V you could get away with using 8AWG AL cable that would only have 5% voltage drop. Even 100ft of 6 AWG (6-6-6) AL cable would run only about $100 compared to $160 just for two sets of 12-2 copper.

If you want to use your current charge controller that can only handle 3 in series for 66V you could still use that 6-6-6 AL cable which would be about 5% voltage loss for 2 parallel strings or about 8% if you added another set of 3.. but still would be better to get a charge controller that allows higher voltage if you plan to expand in future.

You are pushing ~66v at ~22a max so 10awg should do it.
That doesn't allow for any room for expansion and is already at 8.3% voltage drop if using copper which is SUPER expensive now :)
 

iamrich

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That doesn't allow for any room for expansion and is already at 8.3% voltage drop if using copper which is SUPER expensive now :)
He has no room for expansion anyway, but I can't argue with the cost of copper being crazy :D
 

wiseacre

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everyone has been more than helpful in getting me on the right tract.

I've already arranged to send back the controller.
AMPINVT 60 amp 12V/24V/36V/48v DC 150V PV Input MPPT Solar Charge Controller

I have a Eco Worthy kit with a PWM
I added a Moes ATS but now I'd like to get rid of that too and get a whole new setup basically just keeping the panels. Much more user friendly keeping all the disparate components in one unit

Now on my wish list is a Growatt SPF 3000TL LVM
https://www.ginverter.com/Off-Grid-Storage-Inverters/44-589.html
max PV array power - 2000w
MPPT range @operating voltage - 30vdc - 115vdc
max PV open circuit voltage - 145vdc
max solar charge current - 80A

rhino
that's what I needed to hear - increase voltage and get a controller that will handle it. I'm still confused but headed in the right tract.
The Growatt is looking a bit tarnished now.

Any suggestions, I'm not adverse to high prices if the quality is there and allows me to expand in the future. A larger Growatt maybe?

What I want is an inverter with a ATS so I can use the solar power I do produce and auto switch to the grid when my battery bank hits a low point of DOD. Turning off a inbuilt charger (as in the Growatt) and using a separate charge controller with a higher input capacity sounds doable.
 

MisterSandals

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max PV open circuit voltage - 145vdc
That sounds like a step in the wrong direction. Your primary goal should be to get an SCC that accepts a higher max input voltage. If you can get one that will accept all your panels in series, that's probably going to be the most efficient (cost and energy-wise) thing you can do.
 

rhino

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There are Growatts that will take much higher voltages such as the SPF5000US which will take up to 450V DC. Some versions they have even have multiple independent MPPT inputs so you could have 2 separate arrays go into same all in one. I believe the ones with the lower voltage limit like you mentioned are the older ones. One thing to take note about some of these cheaper all-in-ones is they tend to be noisy because of a fan running constantly to cool them off. I almost considered an MPP solar LV model until I found out the fan was really noisy and ran constantly :)
 

MisterSandals

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Some versions they have even have multiple independent MPPT inputs so you could have 2 separate arrays go into same all in one.
Running 2 separate sets of wires with 100ft distance, and half of his highest possible voltage does not sound optimal.
 

rhino

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FYI, for my arrays that are 500ft+ away I am using 2AWG AL cables and Victron 250V charge controllers.
 
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