Combine on the roof or in garage?

[rubiks1]

Hello!

Does it matter where you combine the panels? Lets say I have 6 200 watt panels and a 24 volt system. So that would be 3 strings of 2.  If I combine on the roof it will be a 35 foot run for one of the strings and a 25 foot run for the other 2 if I mount the combiner box to the rack and bring down a #6 pos and neg to the epanel. Or I could create extensions for all of the strings and run them another 30 feet to get them into the garage and mount the combiner there.

So for one set of panels we are looking at a max of a 70 foot run from the panel to the combiner in the garage, for the other two it would be close to 50 feet.

Thanks

[Westbranch]

you need to figure out the costs the different wire size you would use and the wire losses for each example and decide which factor over-rides the other.

Efficiency vs cost.

You need to use a voltage loss calculator like this one...http://www.windsun.com/Hardware/Voltage_Calc.htm

[rubiks1]

Lets go with open circuit at 32 per panel, 2 panels wired in series for a total of 64 volts and if I remember right the isc is 8.75. And this will be the same for all of the strings
The results are

Results:
A maximum distance of 104.56 feet will limit the voltage drop to 3% or less with a 10 AWG Copper conductor delivering 8.75 amps on a 64 volt system.

So I should be just fine with running this to the garage.

Thanks for the voltage calculator. I am bookmarking that url

[dgd]

Open circuit panel voltage is meaningless in your calculation. You should be working with the Maximum power voltage as that is the voltage you may get at the rated current of the panel.

dgd

[mike90045]

Don't forget to put a  price on ease of access.  If you have to troubleshoot an array problem, is it easier to stand on the ground and flip breakers, or crawl up on a toasty or icy roof to do it ?