Dc Overcurrent Protection; Table 1, Recommended Dc Wire/Overcurrent Device - Magnum Energy MMS1012 Owner's Manual

Table 1, Recommended DC Wire/Overcurrent Device

Maximum Continuous
Current¹
DC Grounding
Electrode Wire Size
Minimum DC Wire Size
(90˚C rating in free air)
Maximum DC
Fuse Size
Info: The term "in free air" is defi ned by the NEC as not
encased in conduit or raceway.
If the inverter is expected to operate at a distance greater than
three feet from the battery bank, the DC wire size will need to be
increased to overcome the increase in resistance – which affects the
performance of the inverter. Continue to use the overcurrent device
and DC ground wire previously determined from Table 1 and then,
refer to Table 2 to determine the minimum DC wire size you need for
various distances based on your inverter model.

DC Overcurrent Protection

For safety and to comply with NEC (National Electrical Code) electrical
code regulations, you must install a DC overcurrent protection device
in the positive DC cable line to protect your DC cables. This DC
overcurrent device can be a fuse or circuit-breaker, but 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. See Table 1 to select the DC overcurrent device based on the
minimum wire size for your inverter model.
Note 1 - Maximum Continuous Current is based on the inverter's continuous
power rating at the lowest input voltage with an ineffi ciency factor.
Note 2 - Per the NEC, the DC grounding electrode conductor can be a #6 AWG
conductor if that is the only connection to the grounding electrode and that
grounding electrode is a pipe, rod, or plate electrode.
Note 3 - Wire size is based on the requirements needed to increase effi ciency
and reduce stress to the inverter.
Note 4 - The next larger standard size overcurrent device may be used if
the de-rated cable ampacity falls between the standard overcurrent devices
found in the NEC.
© 2010 Magnum Energy, Inc.
2.0 Installation
Inverter Model
MMS1012 MMS1012-G
200 amps
# 6 AWG
# 1/0 AWG # 1/0 AWG
(260 amps) (260 amps)
300 amps with 300 amps with
time delay
200 amps
# 6 AWG
time delay
15