Page 12
©
2017 Sensata Technologies
Installation
2.2 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 Figure 2-1 and Figure 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 are 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. To avoid polarity problems, color code the
DC cables/wires with colored tape or heat shrink tubing: RED for positive (+), WHITE
for negative (–), and GREEN for DC ground.
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 following guidelines 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 percent 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 connections to the battery terminals 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 Nm). 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 live battery cables to the inverter’s DC
terminals; this is normal and due to the inverter’s internal capacitors being charged.
