Yet another cable size question

[EastTexCowboy]

I have a question on cabling past a Y connector. I'm installing a system with 16 445W panels, a MPP 6548 invertor, and at least 2 of the EG4 5kwh batteries. The panels will be in four arrays with four in each array in series. By my calculations that's about 200W and 11 amps per array before the Y and 200W and 22 amps after combining two arrays with the Y. I'm going to have to run about 135' on the longest run (maybe a little less but I'm allowing a little extra). I have a good location for a Y connector about 60' from the panels. If I install the Y and I'm running 10 awg pv cable from the panels to the Y, can I continue with 10 awg cable for the remainder of the distance? What I'm not sure about is how the Y connector impacts the cable length. If I were carrying 22 amps for the entire distance I would have to go with 8awg based on the online cable size calulators. Since I'm splitting it I'm not sure. Here's a rough sketch.

Any advice much appreciated! I'm going to have another post about the whole earth ground, equipment ground thing and my head is spinning from so many videos and opinions on correct grounding. But that's for another day.

 

[TorC]

For wire ampacity, you can stick with 10ga. That's standard for a 30A circuit. However, what you run into now are line loss issues. From here it's up to your discretion as to how much you spend on wire, how much you might potentially expand, and what you are willing to tolerate for losses. You don't have hard limits on end of run voltage drop because the MPPT will adjust.

Your losses are going to be greatest at the time you have the most power to burn - in full sun. As the MPP amperage goes down your losses go down faster.

If you keep to 10ga for the whole length your total line loss will be about ~2.9% at full power. Just going to 8ga for the 22A section drops that to ~2.1%.

 

[EastTexCowboy]

Thanks! That helps a ton. I'll probably stick with the 10 ga for this run. On expansion, I have another MPP 6548 on the shelf and it looks like I'll have a total of 4 of the EG4 batteries so I could double the solar panels later without a lot of extra expense other than the panels. I'm mostly doing this setup to get a feel for it and see how well it does. I'm installing 2" conduit underground for the last run to the inverter and will have an extra pull string in it. I guess I can always change the wire later if I just can't live with the loss, but frankly I suspect I won't be putting a full load on it that often. I appreciate your expertise!