Can someone please verify that I am doing this correctly. I am connecting 21 solar inverters to a 3 phase 4 wire 277/480 VAC panel. These inverters have a single pole 277 V output. 3 phases 7 inverters per phase 500 feet back to main service.

Assuming max/output "load" of 177 amps per phase

Here is the voltage drop formula that I am using

VD= 1.73 . 12.9 . I . L/CM

my inputs are

1. 1.73

2. 12.9 "approx" K value for copper

3. 177 amps max output I

4 500 feet distance back to service

5 CM = 300,000 300mcm

My results are this VD= 6.58 V or 2.3% vd

The engineer I am working with on this project comes out with a wire size that is 600 MCM to achieve the same VD and his methods are cryptic at least to me.

Please someone tell me that I have no idea what I am doing or confirm this is an acceptable result

thanks

Assuming max/output "load" of 177 amps per phase

Here is the voltage drop formula that I am using

VD= 1.73 . 12.9 . I . L/CM

my inputs are

1. 1.73

2. 12.9 "approx" K value for copper

3. 177 amps max output I

4 500 feet distance back to service

5 CM = 300,000 300mcm

My results are this VD= 6.58 V or 2.3% vd

The engineer I am working with on this project comes out with a wire size that is 600 MCM to achieve the same VD and his methods are cryptic at least to me.

Please someone tell me that I have no idea what I am doing or confirm this is an acceptable result

thanks

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