Changes to 2014 NEC Interconnection Rule 705.12
41
705.12(D) Point of Connection Utility Interactive Inverters By Richard Stovall, CEO SolPowerPeople #SolarMOOC Webinar 12/19/13 12PM CST
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Richard Stovall's (SolPowerPeople CEO, Instructor) review of the new 2014 rules for interconnection of solar PV systems.
Transcript of Changes to 2014 NEC Interconnection Rule 705.12
705.12(D) Point of Connection
Utility Interactive InvertersBy
Richard Stovall, CEO SolPowerPeople#SolarMOOC Webinar 12/19/13
12PM CST
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.
705.12(D)(2)
(1)Feeders(2)Taps(3)Busbars
705.12(D)(2)(1)
2014: Utility Interactive Inverters Feeder Conductor Ampere Rating
705.12(D)(2)(1)(a)
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.
400A
225A
100A 200A
225A
200A
1000A Bus
30A
50A
50A 50A
50A
.
.......
......
200A
200A
PV – 160A Continuous
400A Bus
200A + (160A x 1.25) = 400A600kcmil
.. 200A
200A200A, 3/0 AWG rated at 200A at 75ºC, Table 310.15(B)(16)
MLO
Table 310.15(B)(16)
Table 310.15(B)(16)
2014: Utility Interactive Inverters Feeder Conductor Ampere Rating
705.12(D)(2)(1)(b)
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.
400A
225A
100A 200A
225A
200A
1000A Bus
.
.......
200A
PV – 160A Continuous
200A Bus
.
.200A
200A
.
. .200A20
0A
200A, 3/0 AWG rated at 200A at 75ºC, Table 310.15(B)(16)
Table 310.15(B)(16)
705.12(D)(2)(2)
Feeder – 10 Ft. Tap705.12(D)(2)(2)
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).
400A
225A
100A 200A
225A
200A
1000A Bus
30A
50A
50A 50A
50A
.
.......
......
200A
200A
PV – 160A Continuous
400A Bus
.
.
. ..
LOAD
LOAD
LOAD LOAD
LOAD
........
100A
30A
20A20A
20A 15A
LOAD
LOAD
LOADS
.
.. ...
200A
200A
333 AWG rated 100A at 75ºC
Minimum Feeder Tap[200A + (160A x 1.25)] x .10 = 40A, but in no case less than the rating of the 100A OCPD
100A Bus
Table 310.15(B)(16)
Taps not over 10ft long
• 240.21(B)(1)
Feeder – 25 Ft. Tap705.12(D)(2)(2)
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).
400A
225A
100A 200A
225A
200A
1000A Bus
30A
50A
50A 50A
50A
.
.......
......
200A
200A
PV – 160A Continuous
400A Bus
.
.
. ..
LOAD
LOAD
LOAD LOAD
LOAD
........
100A
30A
20A20A
20A 15A
LOAD
LOAD
LOADS
.
.. ...
200A
200A
331/0 AWG rated 150A at 75ºC
Minimum Feeder Tap Size[200A + (160A x 1.25) x .33 = 133A
100A Bus
Table 310.15(B)(16)
Taps not over 25ft long
• 240.21(B)(2)
EC&M Article on Feeder Taps
• Written by Mike Holt• http://ecmweb.com/code-basics/feeder-taps
705.12(D)(2)(3)(a)
AKA 100% RULE
200A MAIN
PV SUPPLY OCPD
225A BUS
200A MAIN
PV 25A OCPD
225A BUS
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 SUPPLY OCPD
225A BUS
PV SUPPLY OCPD
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
PV SUPPLY OCPD
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 20A OCPD
225A BUS
PV 20A OCPD
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.
705.12(D)(2)(3)(b)
AKA 120% RULE
200A MAIN
PV SUPPLY OCPD
225A BUS
200A MAIN
PV 70A OCPD
225A BUS
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 SUPPLY OCPD
225A BUS
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 20A OCPD
225A BUS
PV 20A OCPD
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
PV 20A OCPD
PV 20A OCPD
TOTAL: 80A PV OCPD, OKAY IN 2014 CODE
200A MAIN
PV 20A OCPD
225A BUS
PV 20A OCPD
PV 20A OCPD
PV 20A OCPD
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.
705.12(D)(2)(3)(c)
200A MAIN
20A 2-POLE PV OCPD
225A BUS
25A 2-POLE
50A 2-POLE20A 2-POLE PV OCPD
20A 2-POLE PV OCPD
15A 1-POLE30A 1-POLE
60A 2-POLE
EMPTY
200A MAIN
20A 2-POLE PV OCPD
225A BUS
25A 2-POLE
50A 2-POLE20A 2-POLE PV OCPD
20A 2-POLE PV OCPD
15A 1-POLE30A 1-POLE
60A 2-POLE
EMPTY
LINE A LINE B
25 25
20 20
20 20
20 20
50 50
60 60
30 15
225 210
705.12(D)(2)(3)(d)
705.12(D)(3)
705.12(D)(4)
LOAD LINE
NOT SUITABLE FOR BACKFEED
705.12(D)(5)
705.12(D)(6)
THANK YOU!!
• Richard Stovall• CEO SolPowerPeople• [email protected]• 512-825-3051• www.solpowerpeople.com
