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Inverter Overcurrent and Cable Sizing - Courtesy of Kyocera Solar Appendix D
117
Inverter Overcurrent and Cable Sizing - Courtesy of Kyocera Solar
Brand
Model
Max.
Continuous
Power (Watts)
Voltage
Max. Input
Amps* DC
Min.
Overcurrent
Protection
(Breaker/Fuse)
Min. Cable
Size**
(In conduit)
Min. Cable Size
**
(In free air)
XANTREX
PORTAWATTZ 600
600
12
80
80
#4
#8
PORTAWATTZ 1000
800
12
107
110
#2
#4
PORTAWATTZ 1750
1500
12
201
200
#3/0
#1
PORTAWATTZ 3000
2500
12
334
350
350 MCM
#3/0
PROSINE 1000-12
1000
12
134
150
#1
#3
PROSINE 1800-12
1800
12
241
250
#4/0
#1/0
PROSINE 2000-12
2000
12
267
350
250 MCM
#2/0
PROSINE 2500-12
2500
12
334
350
350 MCM
#3/0
PROSINE 2500-24
2500
24
167
175
#2/0
#2
PROSINE 3000-12
3000
12
400
400
500 current-and-Cable-Sizing---Courtesy-of-Kyocera-Solar/' >MCM
#4/0
PROSINE 3000-24
3000
24
200
200
#3/0
#1
UX612
2
600
12
80
80
#2
#2
UX1112
2
1100
12
147
150
#2/0
#2/0
UX1412
2
1400
12
187
200
#4/0
#4/0
DR1512
2
1500
12
201
200
#4/0
#4/0
DR2412
2
2400
12
321
350
#4/0
#4/0
1
DR1524
2
1500
24
100
100
#2/0
#2/0
DR2424
2
2400
24
160
175
#2/0
#2/0
DR3624
2
3600
24
241
250
#4/0
#4/0
1
SW2524
2
2500
24
167
175
#2/0
#2/0
SW2548
2
2500
48
84
100
#2/0
#2/0
SW4024
2
4000
24
267
250
#4/0
#4/0
1
SW4048
2
4000
48
134
150
#2/0
#2/0
SW5548
2
5500
48
184
200
#4/0
#4/0
OutBack
FX 2012
2
2000
12
202
250/300
#4/0
#4/0
FX 2524
2
2500
24
101
175/200
#2/0
#2/0
FX 3048
2
2500
48
63
100/110
#2
#2
VFX 2812
2
2800
12
282
250/300
#4/0
#4/0
VFX 3524
2
3500
24
176
250/300
#4/0
#4/0
VFX 3648
2
3600
48
91
175/200
#2/0
#2/0
GTFX 2524
2500
24
126
175/200
#4/0
#4/0
GTFX 3048
3000
48
76
100/110
#2/0
#2/0
GVFX 3524
3500
24
176
250/300
#4/0
#4/0
GVFX 3648
3600
48
91
175/200
#2/0
#2/0
* The maximum input current is calculated by multiplying the inverter's maximum continuous power output by 1.25 and then dividing by 0.85 and the lowest voltage that the inverter will operate at (11V
for a 12V unit, 22V for a 24V unit and 44V for a 48V unit). For example, a SW4024 is a 24V unit with a 4000W continuous output so you would multiply 4000W by 1.25 to get 5000W. You would then divide
5000W by the lowest inverter efficiency of 0.85 to get 5882.4W and then divide that by the lowest inverter voltage of 22 volts to get 267 amps. We downsize the overcurrent protection to 250 amps for the
SW4024 so that we can still use #4/0 AWG cables.
* With OutBack inverters, the full power efficiency should be calculated with a lowest expected full power eficiency factor of 0.90 instead of 0.85 as used with the other brands of inverters.
2
The cable size is the same for free air as in conduit. This preserves the performance of the inverter (motor starting surge) and maximizes the conversion efficiency of the system.
** Minimum cable sizes are for 90� C rated cable from NEC Tables 310-16 & 310-17. Also refer to NEC articles 240-3b and 240-6a for proper sizing of overcurrent protection devices. Cable sizes are good up
to 10' of one way distance. If you use "free air" size cable in conduit, the NEC requires that you use double conductors (two positive and two negative cables). Multiply the rated cable ampacity by 0.8 for
parallel conductors.
Smaller cable sizes than those listed here may be used as long as the overcurrent protection is reduced as well. We typically sell #2, #2/0 and #4/0 AWG inverter cables that should be matched with 110A,
175A and 250A overcurrent protection devices respectively. Using larger cables is perfectly acceptable, but you might run into problems fitting them into various disconnects and fuse blocks.
MCM stands for "thousands of circular mils" and it represents the cross sectional area of cables larger than #4/0 AWG. See NEC Table 8 "Conductor Properties" for details.
1
Cable is sized for 10 feet total length. From 10 feet to 20 feet total length, double the recommended wire size.
2
Cable sizes are recommended by the manufacturer for inverter performance, i.e. surging, ripple and voltage drop. For that reason, cable size given is the same for conduit and free air.