Magnum Energy MS-G Series - Manual (Page 22)

Page 14
©
2015 Sensata Technologies
Installation
2.4 DC Wiring
This section describes the inverter’s required DC wire sizes, the recommended disconnect/
overcurrent protection, and how to make the DC connections to the inverter and the battery bank.
Refer to Figure 2-6 when connecting the DC wires.
Note: Figure 2-6 shows the MS-G attached to MMP enclosure.
WARNING: Even though DC voltage is “low voltage”, signifi 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. Color code the DC cables/wires with colored tape or
heat shrink tubing: RED for positive (+); WHITE for negative (–); and GREEN (or bare
copper) for DC ground, to avoid polarity problems.
CAUTION: To remove battery power from the inverter, disconnect the battery positive
connection before the negative connection. This requirement can prevent damage to
the inverter and/or an accessory connected to the inverter.
Note: When an accessory that is not powered by the inverter (e.g., ME-AGS-N and ME-
BMK) is installed and connected to the inverter (via a network communication cable),
the battery negative connection of the inverter and each accessory must be at the same
potential (i.e., electrically common with each other) until the positive connection of
each device is removed. This prevents a high impedance path developing between the
connected devices (i.e., inverter and accessories), which can cause the network cable
to become the DC return path to the battery—possibly resulting in permanent damage
to all connected devices on the network. This can be prevented if the battery negative
connection of each device is always connected before connecting/disconnecting any
battery positive.
CAUTION: Before wiring the DC cables, review the safety information at the beginning
of this manual and the information below to ensure a safe and long-lived system.
• 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 (15.2 cm). This
helps improve 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 connection points may loosen during use.
• Check all wiring to the battery terminals periodically (once a month) for proper tightness. The
torque requirement for the DC terminals is between 10 to 12 lbf-ft (13.6 to 16.3 N-m). Be
aware that overtightening or misthreading the nuts on the DC terminals can cause the bolts
to strip and snap/break off.
• 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.