two livable buildings and solar on 330 feet of wire. Good idea or not.

[bilede]

I am looking to add a second livable building about 330 feet directly south from my main panel and wondering if there are any negatives to my current idea I am not thinking about and your opinion if it’s a good plan. I have a 400A combo meter main with two 200A breakers, one is fuller, the other has some room if I move things around a little. I currently have a 125A sub-panel that feeds a tac shed primarily for lights that is 150 feet towards the new building site and solar site.

My idea is to upgrade the 125A sub-panel and wire with 200A capacity because there is currently 2“ pvc conduit already in place so no landscaping and concrete needs to come out.. From that sub-panel, a new conduit would be installed continuing 130 feet to another 200A sub-panel. This second sub-panel is where a solar array feeding 40 with 200A main breaker (or 90 if I reduce my main to a 150A breaker) of power would be connected and then another conduit installed continuing the final 50 feet south to a third 200A sub-panel on the new building.

As stated, the first 150 feet is using 2” conduit which is probably going to require copper as large as can be installed. The other 180 feet probably will get 3” so wire could be changed to larger aluminum wire to reduce any voltage loss and cost.

How will the array inputting power closer to the end of the wire and closer to the new building react? Will this help stabilize voltage drop? My biggest consumption is for AC during the day in the warmer months.
I understand the main breaker gets derated to a 150A but what goes into each sub-panel feeding the next sub-panel? A 200 or another 150?

Thanks for your help.

[bcroe]

I am looking to add a second livable building about 330 feet directly south from my main panel and wondering if there are any negatives to my current idea I am not thinking about and your opinion if it’s a good plan. I have a 400A combo meter main with two 200A breakers, one is fuller, the other has some room if I move things around a little. I currently have a 125A sub-panel that feeds a tac shed primarily for lights that is 150 feet towards the new building site and solar site.

My idea is to upgrade the 125A sub-panel and wire with 200A capacity because there is currently 2“ pvc conduit already in place so no landscaping and concrete needs to come out.. From that sub-panel, a new conduit would be installed continuing 130 feet to another 200A sub-panel. This second sub-panel is where a solar array feeding 40 with 200A main breaker (or 90 if I reduce my main to a 150A breaker) of power would be connected and then another conduit installed continuing the final 50 feet south to a third 200A sub-panel on the new building.

As stated, the first 150 feet is using 2” conduit which is probably going to require copper as large as can be installed. The other 180 feet probably will get 3” so wire could be changed to larger aluminum wire to reduce any voltage loss and cost.

How will the array inputting power closer to the end of the wire and closer to the new building react? Will this help stabilize voltage drop? My biggest consumption is for AC during the day in the warmer months.
I understand the main breaker gets derated to a 150A but what goes into each sub-panel feeding the next sub-panel? A 200 or another 150?

You can figure the wire loop lengths needed to connect. With the
power level known, calculate wire size (translated to resistance)
and energy loss. With 750 feet between my southern most panel
and my PoCo transformer, I managed to equip to keep the DC and
AC section losses down to 1%. This involved using larger wire than
the service actually required.

Aluminum wire must be 2 gauges larger conductors to equal copper
performance, but even so it is far cheaper. Using made up Triplex
might be the cheapest and most convenient. This is direct burial
without any of the problems with conduit, but regs say 24 inches deep
vs 18 inches for conduit. The Triplex has a smaller neutral than the
240VAC lines, not a problem since inverters operate at 240VAC and
the neutral has little to do. Burying new wire was not a problem here
since I own a tiny trencher.

Map it all out and do the calculations. One thing to consider, if your
AC losses reach several percent, your inverters are far more likely
to be tripping out from high line voltage. good luck, Bruce Roe

[bilede]

Thank you Bruce for responding. I thought mine was far at 350ish feet but 750 is far.

I am hoping someone has a distance with array connected at the other end with loads also to let me know if this helped keep voltage drop down or not. any other experiences out there similar?