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©
2009 Magnum Energy Inc
.
Installation
2.4 DC
Wiring
This section describes the inverter’s required DC wire sizes and the recommended disconnect/
overcurrent protection and how to make the DC connections to the inverter and the
battery bank.
Refer to
fi
gure 2-4 when connecting the DC wires.
WARNING:
Even though DC voltage is “low voltage”, signi
fi
cant hazards may be
present, particularly from short circuits of the battery system.
CAUTION:
The inverter is NOT reverse polarity protected which means that if the
negative and positive battery voltage is connected backwards to the inverter, the
inverter will likely be damaged. You should verify the correct voltage polarity using a
voltmeter BEFORE connecting the DC wires.
CAUTION:
Before wiring the DC cables, review the safety information at the beginning
of this manual and the following to ensure a safe and long-lived system.
Info:
DO NOT connect the battery cables to the inverter until all wiring is complete and
the correct DC voltage and polarity has been veri
fi
ed.
When the inverter is installed in a Photovoltaic System, the NEC requires that the DC circuit
conductors and overcurrent devices to the inverter be sized to carry not less than 125% of
the inverter’s maximum current rating.
The DC positive and negative cables connected to the inverter from the battery bank should
be tied together with wire ties or electrical tape approximately every 6 inches. This helps
improves the surge capability and reduces the effects of inductance, which improves the
inverter waveform and reduces the wear of the inverter’s
fi
lter capacitors.
Crimped and sealed copper ring terminal lugs with a 5/16” hole should be used to connect the
DC wires to the inverter’s DC terminals.
The battery bank voltage MUST match the DC voltage required by the inverter (i.e., 24-volt
battery bank for a 24-volt inverter) or the inverter may be damaged.
To ensure the maximum performance from the inverter, all connections from the battery bank
to the inverter should be minimized, the exception is the DC overcurrent disconnect in the
positive line and a shunt in the negative line. Any other additional connection will contribute
to additional voltage drops and these extra connections points may loosen during use.
All wiring to the battery terminals should be checked periodically (once a month) for proper
tightness. The torque requirement for the DC terminals is between 10 to 12 ft lbf (13.6
to 16.3 N-m). If you don’t have a torque wrench, ensure all DC terminals are tight and
cannot move.
Be aware that overtightening or misthreading the nuts on the DC terminals can cause the
bolts to strip and snap/break off.
Make sure cables have a smooth bend radius and do not become kinked. Place long cable
runs in conduit and follow existing wire runs where possible.
A brief spark or arc may occur when connecting the battery cables to the inverter DC terminals;
this is normal and due to the inverter’s internal capacitors being charged.
Color code the DC cables/wires with colored tape or heat shrink tubing: RED for positive (+);
WHITE for negative (-); and GREEN for DC ground to avoid polarity problems.
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