Wire sizing

[Shubedobedo]

I'm pretty sure I know the answer but want to double check.

I have 12.88amps pv. Can I use 12 awg for the run with 3 strings?

From what I read you have to up size it by 25%. That bring it up to 16.1amps. Then you need to Derating by 80% because I am doing 3 strings in a single conduit. 12 awg is 20 amp * .8 = 16amps.

That make me think that I must go to 10 awg. I'd love some feed back if I have anything wrong.

 

[DPC]

I'm pretty sure I know the answer but want to double check.

I have 12.88amps pv. Can I use 12 awg for the run with 3 strings?

From what I read you have to up size it by 25%. That bring it up to 16.1amps. Then you need to Derating by 80% because I am doing 3 strings in a single conduit. 12 awg is 20 amp * .8 = 16amps.

That make me think that I must go to 10 awg. I'd love some feed back if I have anything wrong.

It also depends on the voltage.
Tell us the specs on what you want to do and we can do a wire size calculation
( distance voltage and current )

 

[Shubedobedo]

It also depends on the voltage.
Tell us the specs on what you want to do and we can do a wire size calculation
( distance voltage and current )

Sure 500v. 250ft.

 

[DPC]

Online Wire Size Calculators & Tables

This wire size calculator will calculate the appropriate wire gauge for a circuit based on amps, voltage, distance, and load. This website provides a wire size calculator, voltage drop calculator, wire ampacity charts and more.

wiresizecalculator.net

#12 - 3% drop...
Being DC you might get a little better in transmission losses but nothing significant

 

[Supervstech]

Sure 500v. 250ft.

12 will work fine, 10 would be better.
More room for add on, and less heat from heavy output.

 

[Supervstech]

12 will work fine, 10 would be better.
More room for add on, and less heat from heavy output.

#10 is 186 each 500' roll, #12 is 112, so with three conductors, thats a savings of 210 over #10

 

[Shubedobedo]

#10 is 186 each 500' roll, #12 is 112, so with three conductors, thats a savings of 210 over #10

well 3 strings but 6 wires though.

 

[GuyG]

That make me think that I must go to 10 awg.

For intermittent loads I don’t mind looking for the minimum required size. For circuits that carry continuous loads every single day, I try to use the maximum possible size, within economic reason. I just hate the idea of watts being turned into unwanted heat.

The cost difference rn between 10 and 12 cu THWN-2 is about nine cents per foot. For your project that amounts to a total difference of $135. Spend it.

Edit: opps, prices changed since I last checked them. 10 awg shot up. Difference is now about $225. But I’d still go with the 10 if you can swing it.

 

[Shubedobedo]

For intermittent loads I don’t mind looking for the minimum required size. For circuits that carry continuous loads every single day, I try to use the maximum possible size, within economic reason. I just hate the idea of watts being turned into unwanted heat.

The cost difference rn between 10 and 12 cu THWN-2 is about nine cents per foot. For your project that amounts to a total difference of $135. Spend it.

Edit: opps, prices changed since I last checked them. 10 awg shot up. Difference is now about $225. But I’d still go with the 10 if you can swing it.

where are you price checking by chance?

 

[GuyG]

500' 10 THHN THWN-2 Stranded Copper Building Wire

THHN THWN-2 Copper Building Wire Allowable Ampacity for Direct Burial: 40 THHN THWN-2 Copper Building Wire Allowable Ampacity in Duct: 40 Application: THHN stands for thermoplastic high heat-resistant nylon. Known for versatility and durability, it is the most common type of building cable. The...

nassaunationalcable.com

 

[Shubedobedo]

Thanks. Is this thwn? I see things saying it is but looking over everything its just stated as thhn.

https://www.lowes.com/pd/Southwire-500-ft-10-AWG-Stranded-Black-Copper-THHN-Wire-By-the-Roll/50163633

 

[DPC]

Its a three percent loss on 12.
bigger wire is probably not cost effective

 

[Backyard]

Using 12AWG at 250', 500V and 12.88A is a 12.96 voltage drop and 167 watt loss per string. Or 500 watts total

10AWG is 7.66V drop, 98.66 watts per string and 296 watts total

Difference is 204 watts

Your ok with using 12AWG THHN for the current and length of run. 3 or more current carrying conductors in raceway is a 0.80 derating factor. So, 20 amps becomes 16. You're at 12.88A so under the limit. At 16A with a 25% circuit breaker or fuse overhead, you're now at 20 amps.

Or you use 10AWG and a 20A breaker or fuse. Both will suffice. It's more about what you are willing to accept for losses and cost to mitigate them

 

[DPC]

How often is he going to peak at 13 amps?