OL1 (Motor Overload):
    Cause: Internal motor overload protection tripped.
+ Solutions: Check the V/f curve, motor rated current, and reduce the motor load.

OL2 (Inverter Overload):
    Cause: Inverter thermal overload protection tripped.
+ Solutions: Check the V/f curve, replace the inverter with a larger rating if necessary, and reduce the motor load.

OT (Over Torque Detection):
    Cause: Inverter output torque is higher than the set level for a specified time.
+ Solutions: Check the over torque detection parameters and reduce the motor load.

UT (Under Torque Detection):
    Cause: Inverter output torque is lower than the set level for a specified time.
+ Solutions: Check the under torque detection parameters and inspect for issues like a sudden drop in load or belt break.

CE (Communication Error): This error occurs when no Modbus communication is received within the time specified in parameter 09-06 (communication error detection time). It is active when parameter 09-07 is set to 0 to 2. Possible causes include a lost connection or a broken wire, or the host computer may have stopped communicating. To troubleshoot, check the connection and the host computer or software.

FB (PID Feedback Loss): This error indicates that the PID feedback signal has fallen below the level specified in parameter 10-12 (PID feedback loss detection level) for the time specified in parameter 10-13 (Feedback loss detection time). It is active when parameter 10-11 is set to 2. Possible causes include a broken feedback signal wire or a broken feedback sensor. To troubleshoot, check the feedback wiring and replace the feedback sensor if necessary.

STO (Safety Switch): This error occurs when the inverter's safety switches are open. It can be caused by the input F1 and F2 terminals not being connected or if parameter 08-30 is set to 1 (Coast to stop) and the digital terminal switch (58) is turned on. To troubleshoot, check the connection of F1 and F2 and ensure that the digital terminal (58) is turned on.

SS1 (Safety Switch): Similar to STO, this error occurs when the inverter's safety switches are open. It is triggered when parameter 08-30 is set to 0 (Deceleration to stop) and the digital terminal switch (58) is turned on. To troubleshoot, check that the digital terminal (58) is turned on.

EF1 to EF5 (External fault S1 to S5): These error codes indicate an external fault at terminals S1 to S5, respectively. The fault is active when the corresponding multifunction digital input is set to 25 (03-00 to 03-04) and the inverter external fault selection (08-24) is set to 0 or 1. Possible causes include an active multifunction digital input external fault or incorrect setting of the multi-function input function. To resolve this, check the wiring and ensure the correct settings.

EF6 (External fault S6): Similar to EF1 to EF5, this error code indicates an external fault at terminal S6. The troubleshooting steps are the same as for EF1 to EF5.

CF07 (Motor control fault): This error code indicates a motor control fault, which can occur if the SLV mode is unable to run the motor. To fix this, perform a rotational or stationary auto-tune and increase the minimum output frequency (01-08).

FU (Fuse open): This error code indicates that the DC bus fuse has blown, which can happen in models with 230V 50HP and above or 460V 75HP and above. Possible causes include damaged IGBTs or a short circuit at the inverter's output terminals. To resolve this, check the IGBTs, check for a short circuit at the inverter output, and replace the inverter if necessary.

LOPBT (Low flow fault) and HIPBT (High flow fault): These error codes indicate low and high flow faults, respectively. They can occur if the HVAC feedback value is lower or higher than the limits of minimum or maximum flow. To troubleshoot, check that the feedback signal is correct and connected, and ensure that the feedback value is within the acceptable range (23-51 for LOPBT and 23-48 for HIPBT).

LPBFT (Low pressure fault) and OPBFT (High pressure fault): These error codes indicate low and high pressure faults, respectively. They can occur if the feedback value of pump pressure is lower or higher than the limits of minimum or maximum pressure. To fix this, check that the feedback signal is correct and connected, and ensure that the feedback value of pressure is within the acceptable range (23-15 for LPBFT and 23-12 for OPBFT).

LSCFT (Low suction fault): This error code indicates a low suction fault, which can occur if there is insufficient water supply in the effluent channel or if the PID difference is higher than its level or the current is lower than the output current level. To resolve this, check the water supply in the effluent channel and ensure it is regular, and check the PID difference and output current level.

CF00 and CF01 (Operator Communication Error 1 and 2): These error codes indicate errors in data transmission between the LCD keypad and the inverter. CF00 occurs when the LCD keypad and inverter cannot transmit data after power on for 5 seconds, while CF01 occurs when data transmission errors persist for more than 2 seconds. To troubleshoot, disconnect the operator and then reconnect, and consider replacing the control board if the issue persists.

CT Fault: This error code indicates a fault in the voltage level of the three-phase input, which can be caused by abnormal input voltage, excessive noise, or a malfunctioning control board. To fix this, check the input voltage signal and the voltage on the control board.

CF20 Double Communication Error: This error code indicates that redundant Profibus and Modbus protocols are being used simultaneously. To resolve this, ensure that only one communication mechanism is used.