New here: Help calculating this

[sunenergy]

Hey guys:

I have the following specs and I am just trying to figure out a few basic things as I am new to the field of Solar:

Sunpower module: P=275W; 39.4Voc; Vmp=31V; Vnom= 20V; Isc= 9.58A; Imp= 8.94A

They are 2 strings of 13 modules each.

So a few things I wanted to fill out was:

DC Open Circuit Voltage = 13 * 39.4 = 512.2 V ----- Is this calculation of mine right?

Uncombined DC short circuit current: 9.58A --- Is this right?

Combined DC Short circuit current: 9.58*2 = 19.16A --- is this right?

DC system size: I am a little confused about how to calculate this. I need help here.

Also, the system has a 6000W inverter with a 240V circuit. What is the nominal operating current of the inverter.

Please help me with these queries. Thank you in advance.

[sensij]

Those aren't Sunpower panels. Maybe you mean SolarWorld?

You should probably compensate your Voc calculation for temperature. One method is to use the temperature coefficient for voltage that is published on the datasheet, and use the minimum design temperature for your location (delta T correction from STC = [minimum temp - 25 deg C]). You can get the minimum design temp here, if you are in the USA:

http://www.solarabcs.org/about/publications/reports/expedited-permit/map/index.html

26 modules of 275 W = DC system size of 7150 W.

They probably want the rated operating current of the inverter... that should come from the datasheet. It is likely to be something around 6000 W / 240 V = 25 A, but use the value on the datasheet.

Your short circuit current calculations look correct. Make sure to apply the appropriate factors when determining the required wire ampacity... 1.56 is typical for PV source and output circuits.