What Gauge Wire for 100 Feet Away From House?

[sjkted]

Hi All,

I am planning to add about 400 watts of panels 100 feet away from the house. I have shading with trees that makes the amount of solar production drop too much at around 3PM each day. What gauge wire should I be using for this? I am planning to connect to a combiner box and then run a feeder cable. I realize there will be a voltage drop but how much is acceptable?

Thanks,

sjkted

 

[TomC4306]

AWG 8
Less than 5%

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

 

[hwy17]

What is your array voltage and your charge controller or other receiving device?

Unlimited drop is acceptable, the only constraint is charge controller limitations. I.e. if the voltage drop prevents the CC input from staying above it's minimum. Also drop = losses of course.

 

[Johno1066]

400watts at say 100 volts gives 4 amps. 8 guage can carry up to 40 amps. I have 6000 watts of strings in 2 sets each using 10 gauge at around 180 volts with a distance of about 110 feet, and have never seen 20 amps from either string, so go figure.

 

[sjkted]

So, from the voltage calculator, if I use 8AWG, 12V, 100 foot and 33 amps (400 watts / 12 volts), it says I have a voltage drop percentage of 42.92%, starting at 12V (I know it's higher, but this is theoretical) and ending at 6.85V. What gives?

What is your array voltage and your charge controller or other receiving device?

This is for a 12V system.

sjkted

 

[hwy17]

This is for a 12V system.

Don't overwhelm us with this much detail, we're simple people.

 

[Johno1066]

Why would you bring 12 volts from your solar panels to your inverter charge controller.

 

[sjkted]

Because at the moment that's how the system is designed.

sjkted

 

[sjkted]

Interesting. It looks like I can charge 48V solar panels to a 12V system in some cases depending on the charge controller. So, I could take the four 12V panels, run them in series to 48V and then drop the gauge size I need in order to supply the charge controller.

sjkted

 

[740GLE]

Why bother with 4 100w panels and just use one 400w panel? 4 times the connections.

Also you keep referencing “12v panels”, you should be more focused on VOC of the panel, which could exceed 20v. So for 4 panels on a cold day you may exceed VOc limit of a 100v SCC.

 

[sjkted]

I already have the four 100 watt panels just sitting there. Yes, I should check the exact voltage. It's probably around 18V.

sjkted

 

[740GLE]

Can’t beat free. Also 4x18v is better for that long of run, just mind VOC max of the SCC.

Do you ever foresee yourself going more than 400w at this location? A larger conductor in the ground will future proof you’re needs.

 

[deeuubee]

It's gonna cost about $500 using the minimum size wire and conduit.
You are better off using #6 wire for maybe $100 more and be ready for future upgrades.

 

[hwy17]

14 is probably adequate for series. If you want future proof, run conduit.

 

[sjkted]

Yep, I am going to run PVC conduit. I'm already renting a trencher for another project and I'm just going to add this on while I have the tool on-site.

sjkted

 

[hwy17]

I ran 3/4" to my panel site and then promptly regretted not springing for 1". 3/4" can hold all the wire I could foreseeably need, but might be some hard pulls. Mine is a 150ft run.

 

[sjkted]

Thanks for all of the responses. It looks like I have a plan here!

sjkted