Changes to 2014 NEC Interconnection Rule 705.12

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Richard Stovall's (SolPowerPeople CEO, Instructor) review of the new 2014 rules for interconnection of solar PV systems.

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  • Slide reproduction from page 6
  • From page 7 – 705.12(D)(2)(b)(1)
  • Slide reproduction from page 6
  • 705.12(D)2(2) 02Page 8
  • Changes to 2014 NEC Interconnection Rule 705.12

    1. 1. 705.12(D) Point of Connection Utility Interactive Inverters By Richard Stovall, CEO SolPowerPeople #SolarMOOC Webinar 12/19/13 12PM CST
    2. 2. 705.12(D)(1) This change is meant to accommodate microinverters and AC module systems where there may be more than one inverter feeding one OCPD.
    3. 3. 705.12(D)(2) (1)Feeders (2)Taps (3)Busbars
    4. 4. 705.12(D)(2)(1)
    5. 5. 2014: Utility Interactive Inverters Feeder Conductor Ampere Rating 705.12(D)(2)(1)(a) 225A 100A 200A 400A . .. . .. .. PV – 160A Continuous . . 200A MLO 200A 200A 200A 200A + (160A x 1.25) = 400A 600kcmil 225A 30A 50A 200A 1000A Bus 200A, 3/0 AWG rated at 200A at 75ºC, Table 310.15(B)(16) 50A . . .. .. 50A 50A 400A Bus The feeder conductor on the load side of the inverter AC output connection must have an ampacity not less than the feeder overcurrent protective device, plus 125% of the inverter output AC circuit rating.
    6. 6. Table 310.15(B)(16)
    7. 7. Table 310.15(B)(16)
    8. 8. PV – 160A Continuous 100A 225A 200A 1000A Bus 200A 200A 200A 225A 200A 200A 200A 400A . .. . .. .. . . .. . 2014: Utility Interactive Inverters Feeder Conductor Ampere Rating 705.12(D)(2)(1)(b) 200A, 3/0 AWG rated at 200A at 75ºC, Table 310.15(B)(16) 200A Bus The feeder conductor on the load side of the inverter AC output connection must have overcurrent protection on the load side of the inverter output AC connection sized not greater than the ampacity of the feeder.
    9. 9. Table 310.15(B)(16)
    10. 10. 705.12(D)(2)(2)
    11. 11. Feeder – 10 Ft. Tap 705.12(D)(2)(2) PV – 160A Continuous Minimum Feeder Tap [200A + (160A x 1.25)] x .10 = 40A, but in no case less than the rating of the 100A OCPD 225A 100A 200A 200A . . . .. . . . . .. . 100A 200A 225A 3 AWG rated 100A33 75ºC at LOAD LOAD 30A 20A 200A 1000A Bus 200A 20A 20A 15A LOAD LOAD LOAD 200A 400A . .. . .. .. . . . . . . .. . . .. . 30A 50A 50A 50A 50A LOAD LOAD LOADS 100A Bus 400A Bus Feeder tap between the feeder overcurrent protection device and the inverter AC output protection device, must have an ampacity not less than the feeder overcurrent protection device, plus 125% of th e inverter output AC circuit current rating in accordance with 240.21(B).
    12. 12. Table 310.15(B)(16)
    13. 13. Taps not over 10ft long • 240.21(B)(1)
    14. 14. Feeder – 25 Ft. Tap 705.12(D)(2)(2) PV – 160A Continuous Minimum Feeder Tap Size [200A + (160A x 1.25) x .33 = 133A . . 200A 225A 100A . . . .. . . . . .. . 100A 200A 225A 1/0 AWG rated 33 150A at 75ºC LOAD LOAD 30A 20A 200A 1000A Bus 200A 20A 20A 15A LOAD LOAD LOAD 200A 400A . .. . .. .. 200A . . . . .. . . .. . 30A 50A 50A 50A 50A LOAD LOAD LOADS 100A Bus 400A Bus Feeder tap between the feeder overcurrent protection device and the inverter AC output protection device, must have an ampacity not less than the feeder overcurrent protection device, plus 125% of the inverter output AC circuit current rating in accordance with 240.21(B).
    15. 15. Table 310.15(B)(16)
    16. 16. Taps not over 25ft long • 240.21(B)(2)
    17. 17. EC&M Article on Feeder Taps • Written by Mike Holt • http://ecmweb.com/code-basics/feeder-taps
    18. 18. 705.12(D)(2)(3)(a) AKA 100% RULE
    19. 19. 200A MAIN PV SUPPLY OCPD 225A BUS
    20. 20. 2011 Code is based on the OCPD of the inverter. Therefore the MAX OCPD fed to this panel in this location is 25A: 225A(busbar rating) minus 200A (main breaker rating) = 25A 200A MAIN PV 25A OCPD 225A BUS
    21. 21. 2014 Code is based on the 125% of the inverter continuous output current. Is there a difference? Yes. There may be more design flexibility with the new rule. 200A MAIN PV SUPPLY OCPD PV SUPPLY OCPD 225A BUS
    22. 22. Example: 2 branch microinverter circuits. With 25A max (inverter continuous output x 125%) Assuming M215 (215Wac) that’s 22 inverters: (25A/(215/240*1.25)=22.32 200A MAIN PV SUPPLY OCPD PV SUPPLY OCPD 225A BUS
    23. 23. Example: 22 microinverters with allowable 20A OCPD per circuit (11 each). In 2011 Code this is not allowable because it violates the 25A max OCPD requirement. 200A MAIN PV 20A OCPD PV 20A OCPD 225A BUS
    24. 24. 705.12(D)(2)(3)(b) AKA 120% RULE
    25. 25. 200A MAIN PV SUPPLY OCPD 225A BUS
    26. 26. 2011 Code is based on the OCPD of the inverter. Therefore the MAX OCPD fed to this panel in this location is 70A: 1.2 X 225A(busbar rating) minus 200A (main breaker rating) = 70A 200A MAIN PV 70A OCPD 225A BUS
    27. 27. 2014 Code is based on the 125% of the inverter continuous output current. Is there a difference? Yes. There may be more design flexibility with the new rule. 200A MAIN PV SUPPLY OCPD 225A BUS
    28. 28. Example: 4 branch microinverter circuits. With 70A max (inverter continuous output x 125%) Assuming M215 (215Wac) that’s 62 inverters: (70A/(215/240*1.25)=62.51 200A MAIN PV 20A OCPD PV 20A OCPD PV 20A OCPD PV 20A OCPD 225A BUS TOTAL: 80A PV OCPD, OKAY IN 2014 CODE
    29. 29. Example: 62 microinverters with 20A OCPD per circuit (15 X 2 and 16 x 2). In 2011 Code this is not allowable because it violates the 70A max OCPD requirement. 200A MAIN PV 20A OCPD PV 20A OCPD PV 20A OCPD PV 20A OCPD 225A BUS
    30. 30. 705.12(D)(2)(3)(c)
    31. 31. 200A MAIN 20A 2-POLE PV OCPD 25A 2-POLE EMPTY 20A 2-POLE PV OCPD 15A 1-POLE 60A 2-POLE 30A 1-POLE 20A 2-POLE PV OCPD 50A 2-POLE 225A BUS
    32. 32. LINE A LINE B 25 25 20 20 20 20 20 20 50 50 60 60 30 15 225 210 200A MAIN 20A 2-POLE PV OCPD 25A 2-POLE EMPTY 20A 2-POLE PV OCPD 15A 1-POLE 60A 2-POLE 30A 1-POLE 20A 2-POLE PV OCPD 50A 2-POLE 225A BUS
    33. 33. 705.12(D)(2)(3)(d)
    34. 34. 705.12(D)(3)
    35. 35. 705.12(D)(4)
    36. 36. NOT SUITABLE FOR BACKFEED LOAD LINE
    37. 37. 705.12(D)(5)
    38. 38. 705.12(D)(6)
    39. 39. THANK YOU!! • • • • • Richard Stovall CEO SolPowerPeople rstovall@solpowerpeople.com 512-825-3051 www.solpowerpeople.com

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