voltage drop requirements

[bealefay]

Sorry if this is obvious, but I am seeking some clarification:

Solar Job: AC combiner after inverter (obviously, but just helping to paint the picture)

I have a 300' run. The maximum amps coming from my AC combiner box is 75. Do I need to multiply this value by 1.25 when sizing wire considering Vd?

I used the quick and dirty southwire phone app and determined that I need #1 thhn. Hope this is correct, already purchased the wire but haven't yet pulled it.

Thanks

 

[Dennis Alwon]

I have never seen a calculation that used 1.25 for what you are doing. I doubt your load is considered continuous

 

[ggunn]

I have never seen a calculation that used 1.25 for what you are doing. I doubt your load is considered continuous

PV inverter output circuits are indeed considered to be continuous but that is irrelevant to voltage drop.

 

[ggunn]

Sorry if this is obvious, but I am seeking some clarification:

Solar Job: AC combiner after inverter (obviously, but just helping to paint the picture)

I have a 300' run. The maximum amps coming from my AC combiner box is 75. Do I need to multiply this value by 1.25 when sizing wire considering Vd?

I used the quick and dirty southwire phone app and determined that I need #1 thhn. Hope this is correct, already purchased the wire but haven't yet pulled it.

Thanks

Assuming you are using 90 degree wire, both the 90 degree ampacity derated for conditions of use (temperature and conduit fill) and the 75 degree ampacity divided by 1.25 of the conductors have to exceed the maximum output current of the inverter(s), and this has nothing to do with voltage drop. You can make your conductors larger to reduce voltage drop, but not smaller.

For 75A of output current in #1 copper your Vd will be about 2.1V. In your Vd calculation you do not multiply the current by 1.25.

 

[Dennis Alwon]

PV inverter output circuits are indeed considered to be continuous but that is irrelevant to voltage drop.

I guess that makes sense-- didn't really think that thru- thanks