WWYD 350ft run high/low voltage DC or AC

[callmeburton]

Here is the decision I am trying to make. I currently have a SMA SI + E Panel + 2x MN 200's prewired NIB waiting to be installed with PV 350ft away.

Details:
We are currently building a new home, on this property we have an out building / greenhouse. The greenhouse is between the PV and the future home so we will fork off the runs there (adds an extra 60ft mid span) to setup the SI and batteries in the greenhouse then run temp power from there while we build.

For phase 1 we will have 1 PV array 18-30 panels depending on options we choose ... all PV is on site right now with, 1 days worth of battery backup ( lifepo4 48v 280ah,) at our current usage (which it should be less when on our build site vs where we live now)

For phase 2 we were going to put up another PV array with a SB for sure given the simplicity of it and pick up another SI at the same time as well as 3-5 days total for battery capacity.

Phase 3 if required we have room for up to 15 panels on an overhang between our first and second floor we could setup if required but it seems overkill, This area might become where we mount our solar hot water tubes.

Do I:

1. Buy a SB 7 preconfigured for island mode (install is 100% off-grid) + buy a isolation transform + sell off MN Epanel configuration
   1. Costs ~$2100 on top of below numbers for the SB / transformer
   2. Some costs might be covered by selling off MN setup
   3. Run 4/0-4/0-2/0 URD with SB at PV array and SI in home(240vac)
      • Allows for AC near array to be used
      • Allows for another array in future on its own SB to tap into same run
      • Costs $3.3/lft (~$1200)
   4. Run 6-6-6 URD (4x wires) for high voltage low amp DC from PV to SB / SI in home(PV DC 488voc / 584 @ -40F voc.)
      • Costs $1/lft (~$1400)
      • requires 1400 lft wire
      • Allows for 2 SB with maxed out inputs
2. Keep MN Epanel configuration and implement with future SB in mind (PV DC 3s3p for about 150voc / 175 @ -40F voc.)
   1. Run ~1400 lft of 4/0-4/0-2/0 URD + run future 6-6-6 wires for SB (Opt 1.2 above but only 700 lft) SI in home
      • Costs $3.3/lft (~3920)
      • Cost $1/lft (~700) for 6-6-6 URD
      • Keeps MN setup in place
        • Allows for MN's to migrate it to panels on building in future (likely max 1 of the 2 since we can't fit too many where I plan to put them)
        • Allows use of 4/0 URD wires to be used by SB in future if MN's migrated off
        • two is one and one is none ... if a SB goes down I need the generator, if a MN goes down I still have another providing half the power

What else am I missing ... different options, equipment, etc. Feel free to bring it to my attention for consideration.

Right now I am seriously leaning toward Option 1, with 1.3 being the wiring strategy ... any trenching option I do is also getting a 12/2 or two for switching purposes and some RG6 just because ... you never know.

If the SB's require coms then I guess I would have to run URD Cat6 cable as well in the same trench to get back to the SI(s) ... that adds about $150 for the SB option

Set me straight, and let me hear it.

 

[callmeburton]

Delayed update:
We found a used SI for ~$1800 which we bought as well as a never used Radian Outback Control Center which we will require to use the new SI with the other SI setup.

We also went ahead and purchased the SB 7.7 and installed it at the panels which required us to update the MN Solar Breakers to 600vdc.

We then ran 3 wires from array 1 to array 2 to the pedestal outside the barn structure we have. Then four wire from barn to house. The EGC is the 3rd wire in the 3 wire setup and 4th wire in the 4 wire setup.

Cost a little more but I think in the long run was the right choice.

 

[hwy17]

You're designing yourself out of a lot of the alternatives anyone could propose.

With high voltage single string runs over the long distance there's no solar breakers needed and it can run on 10-14awg pairs per string.

If you put the SB back somewhere near home you could still do that.