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Low DC generatrix voltage 
protection
1. Check the power supply. 
2. If the power supply is OK,and check if LED light is OK, 
check the voltage PN, if it is 380V, the problem usually comes 
from the main board. And if the light is OFF, disconnect the 
power, check the IGBT, check those dioxides, if the voltage is 
not correct, the inverter board is damaged, change it. 
3. And if those IGBT are OK, which means the inverter board is 
OK, power form rectifier bridge is not correct, check the bridge. 
(Same method as IGBT, disconnect the power, check those 
dioxides are damaged or not). 
4. Usually if F1 exist when compressor start, the possible 
reason is main board. If F1 exist when fan start, it may be 
because of inverter board. 
Transducer module 
temperature too high 
protection
1. Power supply voltage of the unit is low, increase the power 
voltage to the required range.
2. The space between the units is too narrow for heat 
exchange. Increase the space between the units. 
3. Heat exchanger is dirty or something is block on the surface. 
Clean the heat exchanger or remove the obstruction.
4. Fan is not running. Fan motor or fan is broken, Change a 
new fan or fan motor.
5. Water flow rate is low, there is air in system, or pump head 
is not enough. Release the air and reselect the pump. 
6. Water outlet temp.sensor is loosen or broken, reconnect it or 
change a new one. 
PED PCB failure
1. After 5 minutes of power-off interval, power on again and 
observe whether it can be recovered;
2. If it can't be restored, replace PED safety plate, power 
on again, and observe whether it can be restored;
3. If it can not be recovered,  the IPM module board should 
be replaced.