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Long AC cable run or long DC cable run

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  • Long AC cable run or long DC cable run

    I'm talking about a 30kWp PV System. The utility connection is 33kVA. The distance between the panels and the house is 180 meters. What is the best solution for the cable runs? Place the inverter close to the panels and make a long AC cable run or placing the inverter in the house and have a long DC cable run.

    Thanks for your participation

    Regards

  • #2
    Originally posted by Bendesa1962 View Post
    I'm talking about a 30kWp PV System. The utility connection is 33kVA. The distance between the panels and the house is 180 meters. What is the best solution for the cable runs? Place the inverter close to the panels and make a long AC cable run or placing the inverter in the house and have a long DC cable run.

    Thanks for your participation

    Regards
    Whichever is higher voltage. Usually DC is higher voltage
    OutBack FP1 w/ CS6P-250P http://bit.ly/1Sg5VNH

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    • #3
      In this case the AC cable is 4 x 16mm2 and 180 meters long. From my point off view that AC cable is undersized and even dangerous. What do you think?

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      • #4
        16 mm2 puts the wire size at 5 awg, a very unusual size.

        The main problem with using long AC runs is the voltage drop. This causes the inverters to increase the feed in voltage to the point where they might trip. If you make the run AC, then 5 awg wire would give you about 4% of voltage drop assuming 208 3-phase. And yes, it is undersized for your system, so there is that issue as well. You would need to increase the size to 2 awg to get under 2%, but even larger would be better.

        Going with a DC run seems better since the voltage is higher, so voltage drop is not as much of an issue.

        Good luck!

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        • #5
          Put the inverter near to the electric service to minimize AC voltage drop and dropouts. Your inverter's MPPT input will manage the DC drop and the wiring's resistive power loss is proportional to the square of the current flowing - which is why it is desirable to minimize current by having the solar array voltage as high as practical.
          BSEE, R11, NABCEP, Chevy BoltEV, >3000kW installed

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