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Installation
2.4.1
DC Wire Sizing
It is important to use the correct sized DC wire to achieve maximum effi ciency from the system
and to reduce fi re hazards associated with overheating. Always keep your wire runs as short as
practical to prevent low voltage shutdowns and to keep the DC breaker from nuisance tripping (or
open fuses) because of increased current draw. See Table 2-1 to select the minimum DC wire size
(and corresponding overcurrent device) required based on your inverter model. The cable sizes
listed in Table 2-1 are required in order to reduce stress on the inverter, minimize voltage drops,
increase system effi ciency, and ensure the inverter's ability to surge heavy loads.
If the distance from the inverter to the battery bank is >5 feet (1.5 cm), the DC wire needs to
be increased. Longer distances cause an increase in resistance, which aff ects the performance of
the inverter. Use the overcurrent device previously determined from Table 2-1 and then refer to
Table 2-2 to determine the minimum DC wire size needed for various distances.
Table 2-1, Recommended DC Wire/Overcurrent Device for Rated Use
Maximum
Inverter
Continuous
Model
Current
1
MS2000/
267 amps
MS2012
MS2812
373 amps
MS2024
133 amps
MS4024
267 amps
MS4048
133 amps
Note
Maximum continuous current is based on the inverter's continuous power rating at the lowest
1
input voltage with an inverter ineffi ciency factored in.
Note
Copper wire rated with 90°C (194°F) insulation at an ambient temperature of 30°C (86°F),
2
with a multiple cable fi ll factor (0.8) de-rating (if needed).
Note
The next larger standard size overcurrent device may be used if the derated cable ampacity
3
falls between the standard overcurrent devices found in the NEC.
Note
Per NEC, the DC grounding electrode conductor can be a #6 AWG conductor if that is the only
4
connection to the grounding electrode and that grounding electrode is a rod, pipe, or plate electrode.
Note
May not allow continuous operation at full rated power as defi ned by the NEC.
5
2.4.2
DC Overcurrent Protection
DC overcurrent protection is not included in the inverter—for safety reasons and to comply with
electrical code regulations—it must be provided as part of the installation. The DC overcurrent
protection device must be installed in the positive DC cable line, it can be a fuse or a circuit
breaker and must be DC rated. It must be correctly sized according to the size of DC cables being
used, which means it is required to open before the cable reaches its maximum current carrying
capability, thereby preventing a fi re. In a residential or commercial electrical installation, the NEC
requires both overcurrent protection and a disconnect switch. If a circuit breaker is used as the
overcurrent protection device, it can also be used as the required DC disconnect.
Page 17
Using Conduit
Minimum DC
Recommended
Wire Size
DC Breaker
[rating]
Size
2
#4/0 AWG
(107.2 mm
)
2
250 amps
[260 amps]
#4/0 AWG
(107.2 mm
)
250 amps
2
[260 amps]
#1 AWG
(42.4 mm
)
2
150 amps
[150 amps]
#4/0 AWG
(107.2 mm
)
2
250 amps
[260 amps]
#1 AWG
(42.4 mm
)
2
150 amps
[150 amps]
In Free Air
Minimum DC
Maximum DC
Wire Size
[rating]
2
#2/0 AWG
(67.4 mm
)
2
5
[300 amps]
#4/0 AWG
(107.2 mm
)
5
2
[405 amps]
#4 AWG
(107.2 mm
)
2
[140 amps]
#2/0 AWG
(67.4 mm
)
2
5
[300 amps]
#4 AWG
(107.2 mm
)
2
[140 amps]
© 2016 Sensata Technologies
DC
Grounding
Electrode
Fuse Size
3
Wire Size
300 amps
#6 AWG
with time
(13.3 mm
delay
400 amps
#6 AWG
with time
(13.3 mm
delay
150 amps
3
#6 AWG
with time
(13.3 mm
delay
300 amps
#6 AWG
with time
(13.3 mm
delay
150 amps
3
#6 AWG
with time
(13.3 mm
delay
4
)
2
)
2
)
2
)
2
)
2
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