I have three roofs of the same tilt and orientation. They are not large enough to fit a full string, so I have have to split my string between two roofs. I have two options.

Option 1: Have a short cable between the modules in the string on Roof A and Roof B but have a long home run cable.
Option 2: Have a long cable between the modules in the sting on Roof B and Roof C but have a short home run cable.

Am I correct in saying Option 2 is better since it would result in localised voltage and power loss between the modules where as Option 1 will result in Voltage and yield loss of the entire string

How do I calculate this?
Is this 6 of one and half a dozen of the other?

Not enough information, I'd say, how long is a piece of string? You should give a bit more information, under Option 1, what are the short cable and long cable lengths. what is the Voc expected and what is the Isc expected, how many modules in series? any in parallel? and presumably Option 2 is the same Voc and Isc numbers but the cable lengths would be different... you are not specifying whether you are looking at a high Voltage string or a bunch 150V strings paralleled up, the high Voltage strings, with 13A or so Isc require less copper, but if the run is long, 50m or more, then you do want to increase the wire diameter to prevent too much of a loss to creep in...

as @Kalahari Meerkat mentions, a bit more info will help with more accurate answers

if all in series then the homerun should be the longer one as it will be the higher voltage so minimal losses if at least 6mm or 8mm cable. i.e. option 1

Some panels cables are long enough that you can connect every second one to each other.  In my case, I wanted to feed my string of 8 panels from one end, so I connected the odd panels to each other from left to right, and the even panels to each other from right to left, with the two right most panels then connected as well.  I had to flip the even panels around to get the positive and negative connections from one panel to the next close enough together.

In the end the resistance is determined by the total length of the wire from mppt, through all the panels and back to the mppt. I managed to save about 9m of wire being in the circuit by doing the above.

 

Edited October 30, 20232 yr by Paulcupine