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diy solar

Running DC underground from solar panel to meter!

Bob The Builder

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Sep 25, 2021
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I have about a 125 foot run from solar panels to my house meter. I would use copper. What size and kinda of wire and how many individual wires. to minimize lost for a 10 k system?
 
If you are using micro inverters, you will be running AC out to your panels. If you are using a "string" type inverter, you should be running DC voltage maybe in the 200-400 volt range. Without more specific information, a good answer is not possible.
 
More conductor in the ground is always better, I’m gonna say at least 8 awg should do you good. Also pulling that through conduit will be a good workout and set you up for future expansion.

That and the copper manufacturing industry approves.
 
More conductor in the ground is always better, I’m gonna say at least 8 awg should do you good. Also pulling that through conduit will be a good workout and set you up for future expansion.

That and the copper manufacturing industry approves.
My micro inverter capacity is 9600w. I ran #4, 250 feet. I get about 5v drop over the run when it is running full power. Pretty funny to think of a voltage "drop". At the house I am measuring about 245v AC. At the solar array breaker box, I measure 250v AC when it is working hard.
 
I would use copper.
It might be worth your while to price copper and aluminum. An aluminum conductor will have more loss so you will need a larger size to get the same loss as smaller copper. The tables referenced earlier will help.. They are both commodities that fluctuate from time to time. I have a similar run and switched to micros because losses with AC are less. I am still figuring out whether copper or aluminum is the most economical.
 
My micro inverter capacity is 9600w. I ran #4, 250 feet. I get about 5v drop over the run when it is running full power. Pretty funny to think of a voltage "drop". At the house I am measuring about 245v AC. At the solar array breaker box, I measure 250v AC when it is working hard.

That’s not that micro of an inverter ?
 
It would be a mistake to use copper IMHO. Unless the terminals on either end require that.
 
As DThames said, quite a bit depends on the details of your setup, and what you want to plan for in the future. Are you running DC over these 125' or AC? Does your charge controller (or inverter) allow for higher voltages from the panels? Might you want to add more panels in the future? Depending upon how you answer these sorts of questions, you might end up with very different answers.

FWIW, when I was putting my system in (some 20 years ago), I found that the major expense wasn't the size of the wire, but the cost of the backhoe to dig and refill the trench for the wire. The soil moving cost was the same whether I put 6ga or 4/0 wire in (I was using direct burial cable which meets code in my area). So I opt'd to put in way bigger wire size then I needed at the time.

These days, with MPPT charge controllers, and the like built into string inverters, you can put your PVs in series up to fairly high voltages, which greatly reduces power(voltage) loss over long wire runs. That is why knowing if you are planning to move DC over this run may be important, depending upon how high a voltage your CC or string inverter can handle.

If the components of your system are still unpurchased, and the configuration of where they are all located is still changeable, you might want to consider picking a configuration and parts that enable minimal power loss with the flexibility of adding more panels at some future date.
 
It all depends on PV voltage, and current. The higher the voltage, the better.
My panels are all 100' to 200' from (600V max input) GT PV inverters. Multiple runs of 12 awg wire, a pair per PV string. Paralleled, fused if necessary, at the inverters. This allows me to scramble connections as I change inverter models and sizes.
 
If your digging a trench, put in conduit, sooo much easier 10-40 years from now.

Just my 2 cents.
 
A good amount of NoAlox can reduce the oxdation of the Aluminum which means you can make most connectors work as long as you use the right torque and tighten after a few cycles,
It's not that. Certain equipment requires copper wires if you care about not losing the UL listing. If the setup needs to pass inspection, that is of serious consideration.
 
I just completed pulling wire which was almost the same distance as yours. I went overboard and used 4awg copper, looked into aluminum but did not want to mess with the extra connections. There was no voltage drop after checking either.
 
I just completed pulling wire which was almost the same distance as yours. I went overboard and used 4awg copper, looked into aluminum but did not want to mess with the extra connections. There was no voltage drop after checking either.
Thanks, how many wires did you run?
 
Thanks, how many wires did you run?
I ran two pairs for two arrays, I was very lucky to find a great deal on the wire, plus two cat6 cables. Aluminum was much cheaper but having to reduce down for the charge controllers and 3 inch conduit was significantly higher as well.
 
It all depends on PV voltage, and current. The higher the voltage, the better.
My panels are all 100' to 200' from (600V max input) GT PV inverters. Multiple runs of 12 awg wire, a pair per PV string. Paralleled, fused if necessary, at the inverters. This allows me to scramble connections as I change inverter models and sizes.
Ok I swapped the wires from the CTs at the transmitter. It's not adding wattage but the watts are not as high as I am reading at the invertor on my Kill A Watt meter. I read 220 watts at the invertor and it increased 120 watts on my wireless display. It has to backfeed through 120 foot of #2 cable. Now I pulled one wire at a time off the transmitter and the wireless meter dropped about the same for each leg. It's working but not accurate as I'd like. I'm going to try repositioning the CT clamps on the mains.
 
Inverter plugged into power strip with shop fan still on.
 

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Sun not constant with clouds. Watts panels are putting out now was 150 watt going up and down.
 
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