Hi,

Over the next month or so, I will be installing (2) STXR2500's each using (12) Kyocera 158's. The panels will be ground mounted, up off the ground a couple of feet, just in case we get a two-footer snow storm.

I've been debating where to mount the two 2500's. Should I mount them (sheltered) under the panels and run 10 gauge (120VAC) to the house that is 65' away?

Or... Mount the 2500's on the house and run 6 gauge wire(70VDC, 6.8A) from 8 sets of panels.

There is a chance that somewhere in the next 5-10 years that I may go off-grid, so I am leaning towards running the 6 gauge wires, plus the inverters will be better protected.

Curious for your opinions,

Alan

I wouldn't mount them under the array , unless they can remain vertical and far enough from the ground not to suck in critters and such with the fan

Wiring the home runs in 6 Awg isn't that big of a deal , just use 2" PVC (grey) and pull all the home runs all at once. If you would like the Suntie at the array , I would suggest you make some type of dedicated vertical support for the inverter , unit-strut comes to mind.

Regardless of your DC runs and locations , you will need to beef up the AC side , 10 gauge will be OK for short runs but you should do your losses for the inverters maximum VA (figure 230 volts 11 amps) and if you put the Sunties at the array , 200 ft round trip at 22 amps (both inverters max VA) you would be looking at close to a 2% loss in the AC side wiring using 10 gauge , .76% with 6 Gauge

A good what-if helper is the Home-Power Excel spread-sheet http://www.homepower.com/files/wire.xls , it is what I use to properly size the wiring and its free

Hi Henry,

I already have the program. I just have to remember to up the amperage by 156% to comply with the NEC. So if each string is 70VDC @ 6.8A, I must wire for 10.6A. According to Home Power's table, 6 gauge @ 130' round trip = .50% loss. Probably overkill, but so be it.

Thanks,

Alan

If you'd like to save money on wiring costs, it would be better to do the long wiring runs at the higher voltage. So you'd be better off with the SunTie closer to the panels and doing the long wiring run at 230 volts AC instead of the DC 70 volts. However, if the wiring costs are not a problem, you just need a lot more (times # of panel sets) and/or thicker wire to do the long run at 70V dc at acceptable loss levels. I have my SunTie mounted inside my garage. This keeps it nice and clean and the UPG is quiet enough to not to be annoying. Hopefully it will last longer mounted indoors.

Wire is the cheapest (least expensive) part of a PV system .. 6AWG in 500 foot rolls cost 90 bucks at home depot. PVC condiut , even 2" is only 50 cents foot so were only taking 200-300 bucks in materials to have the long runs be the panels to the inverter.

Also , don't neglect the AC side wiring , having 2-3% losses is easy if the number arent computed ! , it is really surprising that the NEC allows I beleive 5% losses in the wiring and this is what most relate to amps to wire size (Just look at the home depot wire chart as an example)