Magnum Energy MMS Series - Manual (Page 22)

© 2014 Magnum Energy, Inc.
Electrical systems in mobile installations typically do not require
using a DC disconnect, although an overcurrent protection device is
still required. Because the DC disconnect is not required, a fuse is
usually used as the disconnect device in these installations. These
installations also do not normally use conduit, so the fuse must be
installed in the ungrounded conductor (usually the positive DC cable
line) within 18 inches (45.7 cm) of the battery—to protect the DC
wiring system.
If using a fuse, we recommend using a
class-T type or equivalent.
This fuse type is rated for DC operation, can handle the high short-
circuit currents, and allows for momentary current surges from the
inverter without opening.
2.2.3 DC Grounding
The inverter/charger should always be connected to a permanent,
grounded wiring system.
The idea is to connect the metallic chassis
of the various enclosures together to have them at the same voltage
potential, which reduces the possibility for electric shock.
For the
majority of installations, the inverter chassis and the negative battery
conductor are connected to the system’s ground bond via a safety-
grounding conductor (bare wire or green insulated wire) at only one
point in the system. Per the NEC, the size for the grounding conductor
is usually based on the size of the overcurrent device used in the DC
system.
Refer to Table 1 to select the appropriate DC ground wire
based on the overcurrent device used for your inverter model.
If the inverter is in a vehicle, DO NOT connect the battery negative
(-) cable to the vehicle’s safety ground. Only connect to the inverter’s
negative battery terminal. If there are any non-factory installed
appliances onboard the vehicle, DO NOT ground them at safety
ground. Only ground them at the negative bus of the DC load center
(as applicable).
2.2.4 DC Cable Connections
When connecting the DC cable to the battery or to the inverter’s DC
terminals, the hardware should be installed in the correct order to
prevent high resistance connections from heating up and possibly
causing the connections to melt. Follow Figures 11 and 12 to stack
the hardware correctly. Tighten the terminal connections from 10
to 12 ft-lbs.
CAUTION: Don’t put anything between the DC cable ring
lug and the battery terminal post or the inverter’s DC
terminal. If antioxidant grease or spray is used, apply
it after all the connections have been made and are
properly tightened.
CAUTION: Overtightening or misthreading nuts on the DC
terminals will cause the bolts to strip and snap/break-off.
Installation
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