solar wire guage sizing

[Scott Off Grid]

I am trying to figure out what wire guage I need to use between the solar panels and the inverter.
This is the panel I am using, on a Sol-Ark 15K inverter.

• Rated Power: 245W
• Open circuit voltage (VOC): 37.3 V
• Max power voltage (VMP): 29.7 V
• Short circuit current (ISC): 8.62 A
• Maximum Power Current (IMP): 8.10 A
• Maximum system voltage: 1000V DC(IEC) / 600V DC(UL)
• Max Fuse Rating: 15 A

My plans are to put 2 rows of 8 panels in series and then parallel the 2 rows together.
The issue is the distance between the panels and the inverter, it's about 80 feet.
Should I use aluminum or copper wire?
What guage should I use?

 

[sunshine_eggo]

I am trying to figure out what wire guage I need to use between the solar panels and the inverter.
This is the panel I amusing

• Rated Power: 245W
• Open circuit voltage (VOC): 37.3 V
• Max power voltage (VMP): 29.7 V
• Short circuit current (ISC): 8.62 A
• Maximum Power Current (IMP): 8.10 A
• Maximum system voltage: 1000V DC(IEC) / 600V DC(UL)
• Max Fuse Rating: 15 A

My plans are to put 2 rows of 8 panels in series and then parallel the 2 rows together.
The issue is the distance between the panels and the inverter, it's about 80 feet.
Should I use aluminum or copper wire?
What guage should I use?

8S = 37.3*8 = 298.4V (use Vmp)
2P = 8.62*2 = 17.24A (use Isc)
80'

0.92% drop w/10awg copper:

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

This is the major benefit of high voltage MPPT. Make sure that your particular MPPT will use the full current from the array = about 17A. Some high voltage MPPT have low PV input current limits around this level.

 

[Scott Off Grid]

This is the major benefit of high voltage MPPT. Make sure that your particular MPPT will use the full current from the array = about 17A. Some high voltage MPPT have low PV input current limits around this level.

I have a Sol-Ark 15k inverter

 

[zanydroid]

I have a Sol-Ark 15k inverter

Paste MPPT spec? Few of us have those numbers memorized for each model.

#10 is simplifies code compliance for this ampacity. #12 copper MAY be OK depending on how you interpret the 20A limit rule

Extremely high likelihood that at least one of the things the wire connects to will not be rated for Aluminum. And aluminum is PITA to find at this AWG, in flexible PV wire, and with meaningful cost savings anyway.

 

[Scott Off Grid]

Paste MPPT spec? Few of us have those numbers memorized for each model.

Input Data (PV)
Max. Allowed PV Power (STC)
19,500W
Nominal Voltage Range
175 - 425V
Startup Voltage
125V
Max. Input Voltage
500V
Max. Input Current per MPPT
26A (self-limiting)
No. of MPP Trackers
3
No. of PV Strings per MPPT
2
Max. AC Coupled Input
19,200 W

 

[zanydroid]

Thanks, I think #10 makes sense.

Since this is 80 ft you probably already need transitions (disconnect at inverter and most likely also at array), and if those disconnects are Aluminum rated (I have not checked) then that CAN be considered, however:

• From panels to disconnect or splice it would be copper PV, from disconnect to inverter it most likely has to be copper (THHN would be easier)
• I suspect #8 THHN aluminum will not save you that much money, however you might be able to find a deal, and if you want to oversize for future expansion (you can go to 3P on that inverter with these panels, but that will exceed #10 copper ampacity) it becomes easier to save money with Aluminum on the larger conductors.

 

[Scott Off Grid]

Thanks, I think #10 makes sense.

Since this is 80 ft you probably already need transitions (disconnect at inverter and most likely also at array), and if those disconnects are Aluminum rated (I have not checked) then that CAN be considered, however:

• From panels to disconnect or splice it would be copper PV, from disconnect to inverter it most likely has to be copper (THHN would be easier)
• I suspect #8 THHN aluminum will not save you that much money, however you might be able to find a deal, and if you want to oversize for future expansion (you can go to 3P on that inverter with these panels, but that will exceed #10 copper ampacity) it becomes easier to save money with Aluminum on the larger conductors.

I did find this PV wire

10 AWG Solar Photovoltaic Wire 2KV UL 4703 (PV Wire)

10 AWG Solar Photovoltaic Wire 2KV UL 4703 (PV Wire)

www.wireandcableyourway.com

 

[zanydroid]

Sure, that is standard, you may need 19 strand to meet code for connecting to solar panels.

For the investment in a SolArk 15k, having someone draft plans with wire type details might not be a bad investment. Possibly also order balance of system components for you. Because there are a lot of little gotchas

 

[zanydroid]

EDIT: IIRC this is for situations where flexibility is required during service. And applicable to solar panel side because panels need to be moved

 

[Scott Off Grid]

Sure, that is standard, you may need 19 strand to meet code for connecting to solar panels.

For the investment in a SolArk 15k, having someone draft plans with wire type details might not be a bad investment. Possibly also order balance of system components for you. Because there are a lot of little gotchas

 

[Utpete]

I’ve used Windy Nation for some pv cable and some big battery cable, 4/0 and 2 gauge. Seems to be quality stuff and free shipping on some of it. 10 gauge pv looks about the same .55 a foot

 

[Scott Off Grid]

based on what I have read above the wire will lose about 60 watts to heat over the 100', to me that seems like a very small amount and shouldn't degrade the wire over time.
Then again I have no point of reference except for holding a 60watt incandescent bulb in my hand.
Any thoughts or opinions on this way of looking at it?

 

[zanydroid]

based on what I have read above the wire will lose about 60 watts to heat over the 100', to me that seems like a very small amount and shouldn't degrade the wire over time.
Then again I have no point of reference except for holding a 60watt incandescent bulb in my hand.
Any thoughts or opinions on this way of looking at it?

If you stay within the NEC ampacity limits it is safe.

The 60W spread over 100' is no big deal, what causes damage is how focused the wattage is. Which typically will be focused at the terminations b/c of (possibly) increased resistance. Also depends on how trapped the heat is, but NEC safety limits and derating adjustments take that into account.

The power loss also is proportionally lower when you're producing less.