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7 Troubleshooting
※ 7.1 Error Message
Sunways STT 4-25kW series three phase inverter is designed in accordance with grid
operation standards, and conform to the requirements of safety and EMC. The inverter
had passed a series of rigorous tests to ensure it runs sustainably and reliably before
shipment.
When a fault occurs, the corresponding error message will be shown on the OLED display,
and in this case, the inverter might stop feeding into grid. The fault messages and their
corresponding troubleshooting methods are listed below:
Error Message
Description
Troubleshooting
No Display
No Display
① Check whether cables are all firmly connected
and DC switch is on.
② Check whether the input voltage meets the
working voltage.
Mains Lost
Grid power outage, AC switch or
circuit is disconnected.
① Check whether the mains supply is lost.
② Check whether the AC breaker and terminals
are well connected.
Grid Voltage Fault
G r i d o v e r v o l t a g e o r
undervoltage, the grid voltage
is higher or lower than the set
protection value.
① Check whether the safety regulation setting is
correct.
② Check the voltage of the grid. If the grid
voltage exceeds the allowed range of inverter
protection parameters, please contact the local
grid company to resolve.
③ Check whether the impendence of the AC
cable is too high. Replace with a thicker AC cable
if that is the case.
7 Troubleshooting
Error Message
Description
Troubleshooting
Grid Frequency
Fault
Grid over frequency or
underfrequency, the grid
frequency is higher or lower than
the set protection value.
① Check whether the safety regulation settings
are correct.
② Check the frequency of the grid. If the grid
frequency exceeds the allowed range of inverter
protection parameters, please contact the local
grid company to resolve.
ISO Over Limitation
Low system insulation resistance,
which is generally caused by
poor insulation to ground of the
module/cable or by rainy and
damp environment.
① Check whether the PV panels, cables, and
connectors are broken or water leaked.
② Check whether there is a reliable inverter
grounding line.
GFCI Fault
Excessive leakage current.
① The ground current is too high.
② Check whether the PV cable has a short circuit
to ground.
PV Over Voltage
PV over voltage is too high.
① Input voltage is too high.
② Reduce the number of PV panels to make sure
the open-circuit voltage of each string is lower
than the inverter max allowed input voltage.
Inverter Over
Temperature
Temperature anomaly, the
temperature of the interior of the
inverter is excessively high and
out of the safe range.
① Check whether the inverter is directly exposed
to the sunlight.
② Reduce ambient temperature.
DCI Fault
DC Injection Hight. Inverter
detects a higher DC component
in AC output.
① Restart the inverter, wait a moment for
inverter recovery.
② If the fault occurs repeatedly, please contact
Sunways.
7 Troubleshooting
