Panel string configuration with partial shade

I am installing a 36 module array in Tahoe consisting of one six module, one twelve module and one eighteen module sub-array. The six panel array has morning shade during June, July, and August. It will be connected to six of the modules at the eighteen module array making three strings of twelve SolarWorld 280s. I will have one SMA 3800TL-US and one SMA 7000TL-US inverter. Which inverter would be best for the partial shaded string? Run it separate to the 3800 or combine it with another string into the 7000? Should I try to achieve similar DC home run lengths from each of the strings? Gregg

Comments

Gregg,

Looking at your design temps for Tahoe area, it appears isolating 6 of the modules onto one MPPT channel of your SB-3800TL and 7 to the other may work. The goal I have in mind is to ensure that your string of six modules is able to meet a minimum of 150V which the inverter requires to start. Using this configuration I came up with 157V which is close to the mark.

If you pick up a 7th module for that string, based on my calculation you would be in a more comfortable range for high temps. So what I propose is to have 7 modules on MPPT A and 7 on MPPT B for the 3800TL. On the 7000TL I suggest MPPT A have 12 and MPPT B have 10.

Does that proposal work for what you have had in mind?

Adam