Troubleshoot your LS Electric S100 VFD with our updated guide. Learn to interpret OCT, OVT, and GFT trips, use DriveView 9 for diagnostics, and reset faults.

LS S100 Fault Codes Reference Table

Below is the reference for the LS S100 protective functions. Please refer to your existing fault list to match the code on your display with the necessary corrective action.

LS S100 Fault Codes List

Fault Code and Meaning	Cause and Remedy
OLt Over Load (Latch)	Cause: Displayed when the motor overload trip is activated and the actual load level exceeds the set level. Remedy: Check motor load and capacity. Operates when Pr.20 is set to a value other than 0.
ULt Under Load (Latch)	Cause: Displayed when the motor underload trip is activated and the actual load level is less than the set level. Remedy: Check for broken belts or pump dry run. Operates when Pr.27 is set to a value other than 0.
OCt Over Current1 (Latch)	Cause: Displayed when inverter output current exceeds 200% of the rated current. Remedy: Check for short circuits or motor insulation failure.
OVt Over Voltage (Latch)	Cause: Displayed when internal DC circuit voltage exceeds the specified value. Remedy: Check input voltage and deceleration time.
LVt Low Voltage (Level)	Cause: Displayed when internal DC circuit voltage is less than the specified value. Remedy: Check input power supply voltage.
LV2 Low Voltage2 (Latch)	Cause: Displayed when internal DC circuit voltage is less than the specified value during inverter operation. Remedy: Check for power fluctuations during operation.
GFt Ground Trip (Latch)	Cause: Displayed when a ground fault trip occurs on the output side of the inverter and causes the current to exceed the specified value. Remedy: Check motor and cabling for ground faults. (Note: S100 inverters 4.0kW or less do not support GFT; they may show OCT or OVT instead).
EtH E-Thermal (Latch)	Cause: Displayed based on inverse time-limit thermal characteristics to prevent motor overheating. Remedy: Check motor load and cooling. Operates when Pr.40 is set to a value other than 0.
POt Out Phase Open (Latch)	Cause: Displayed when a 3-phase inverter output has one or more phases in an open circuit condition. Remedy: Check output wiring. Operates when bit 1 of Pr.05 is set to 1.
IPO In Phase Open (Latch)	Cause: Displayed when a 3-phase inverter input has one or more phases in an open circuit condition. Remedy: Check input wiring and fuses. Operates only when bit 2 of Pr.05 is set to 1.
IOL Inverter OLT (Latch)	Cause: Displayed when the inverter has been protected from overload and resultant overheating (150% for 1 min, 200% for 4 sec). Remedy: Check load duty cycle and inverter capacity.
ntH No Motor Trip (Latch)	Cause: Displayed when the motor is not connected during inverter operation. Remedy: Check motor connection. Operates when Pr.31 is set to 1.
OHt Over Heat (Latch)	Cause: Displayed when the temperature of the inverter heat sink exceeds the specified value. Remedy: Check cooling fan and ambient temperature.
OC2 Over Current2 (Latch)	Cause: Displayed when the DC circuit in the inverter detects a specified level of excessive, short circuit current. Remedy: Check for short circuit in the motor or internal DC circuit issues.
EHt External Trip (Latch)	Cause: Displayed when an external fault signal is provided by the multi-function terminal. Remedy: Check external device status. Requires multi-function input terminals at In.65-71 set to 4.
bX BX (Level)	Cause: Displayed when the inverter output is blocked by a signal provided from the multi-function terminal. Remedy: Check input signal status. Requires multi-function input terminals at In.65-71 set to 5.
HWt H/W-Diag (Fatal)	Cause: Displayed when an error is detected in memory (EEPROM), ADC Offset, or CPU watchdog. Remedy: Fatal Error. Power cycle the unit. If error persists, contact LS ELECTRIC customer service.
ntC NTC Open (Latch)	Cause: Displayed when an error is detected in the temperature sensor of the Insulated Gate Bipolar Transistor (IGBT). Remedy: Contact service center.
FAn Fan Trip (Latch)	Cause: Displayed when an error is detected in the cooling fan. Remedy: Check or replace cooling fan. (Set Pr.79 to 0 to activate fan trip for models below 22kW).
PId Pre-PID Fail (Latch)	Cause: PID feedback is below set value and low feedback continues (treated as load fault). Remedy: Check PID feedback loop and system pressure/flow. Operates with functions set at AP.34–AP.36.
Hbr Ext-Brake (Latch)	Cause: Occurs when the inverter output starting current remains below the set value at Ad.41. Remedy: Check external brake settings. Set either OU.31 or OU.32 to 35 (BR Control).
SFA / SFb Safety A(B) Err (Latch)	Cause: Displayed when at least one of the two safety input signals is off. Remedy: Check safety input wiring and switches.
PtCt PTC Trip (Latch)	Cause: Displayed when a PTC error is detected, PTC value is exceeded, or a fault occurs. Remedy: Check motor PTC sensor and wiring.
LOr Lost Command (Level)	Cause: Frequency or operation command error detected during remote operation (not keypad). Remedy: Check communication lines. Activate by setting Pr.12 to any value other than 0.
IOt IO Board Trip (Latch)	Cause: I/O board or external communication card is not connected or has a bad connection. Remedy: Check connection of the option card.
ErrC Error Code	Cause: Displayed when an error code continues for more than 5 seconds. Remedy: Check specific error sequence displayed.
PAr ParaWrite Trip (Latch)	Cause: Communication fails during parameter writing (LCD keypad usage). Remedy: Check control cable connection between keypad and inverter.
OPt Option Trip-1 (Latch)	Cause: Communication error detected between the inverter and the communication board. Remedy: Check installation of communication option card.
OLW Over Load Warning	Cause: Displayed when the motor is overloaded. Remedy: Operates when Pr.17 is set to 1. Output available via terminal (OU.31/OU.33 set to 5).
ULW Under Load Warning	Cause: Displayed when the motor is underloaded. Remedy: Operates when Pr.25 is set to 1. Output available via terminal (OU.31/OU.33 set to 7).
IOLW INV Over Load Warning	Cause: Displayed when overload time equivalent to 60% of inverter overheat protection level is accumulated. Remedy: Reduce load. Output available via terminal (OU.31/OU.33 set to 6).
LCW Lost Command Warning	Cause: Lost command warning alarm occurs based on condition set at Pr.13-15. Remedy: Check comms. Even if Pr.12 is 0, this warning can occur via digital output (OU.31/OU.33 set to 13).
FAnW Fan Warning	Cause: Displayed when an error is detected from the cooling fan while Pr.79 is set to 1. Remedy: Check fan. Warning signal available via digital output (OU.31/OU.33 set to 8).
EFAn Fan Exchange	Cause: Alarm occurs when the fan life value (Pr.86) is less than the value set at Pr.87. Remedy: Replace fan. Warning signal available via digital output (OU.31/OU.33 set to 37).
dbW DB Warn %ED	Cause: Displayed when the DB resistor usage rate exceeds the set value. Remedy: Check DB resistor sizing. Set detection level at Pr.66.
trEr Retry Tr Tune	Cause: Tr tune error warning alarm is activated when motor's rotor time constant (Tr) is too low or high. Remedy: Check motor parameters. Activated when dr.9 is set to 4.
SLP PID Sleep	Cause: When the PID operation enters sleep mode, a warning occurs. Remedy: Normal operation status during PID sleep.

 

How to Read S100 Faults via DriveView 9

While the 7-segment LED keypad is effective for quick checks, connecting your PC to the drive via the RJ45 port or Mini-USB using LS Electric DriveView 9 software provides a professional-grade diagnostic experience for 2026 standards.

• Fault History (PRT-10 to 14): The S100 records the last 5 major trips. DriveView 9 allows you to view these with detailed snapshots, including the output frequency, motor current, and DC link voltage at the exact millisecond of the trip.
• Status Monitoring: You can monitor real-time I/O terminal status to see if an external interlock or an E-Stop signal is triggering an EXT (External) trip.
• Smart Copier: For rapid field diagnostics, the Smart Copier can be used to download fault logs and parameter sets even without main power applied to the drive.

General Troubleshooting Steps

Before performing a manual reset on your LS S100 drive, perform these essential hardware checks:

1. Overcurrent (OCT): This is often caused by a short circuit or high starting load. If the trip occurs during acceleration, try increasing the ACC time or check if the motor is mechanically seized.
2. Overvoltage (OVT): Typically occurs during deceleration of high-inertia loads. Increase the Deceleration Time (Parameter ADV-04) or ensure the braking resistor is functioning correctly.
3. Ground Fault (GFT): The S100 features highly sensitive leakage protection. Check for moisture in the motor terminals or breakdown in cable insulation, especially in humid or wash-down environments.

Frequently Asked Questions (FAQ)

Q: What is the difference between a “Trip” and a “Warning”?

A: A Trip (e.g., OCT, OVT) instantly cuts power to the motor and requires a manual reset. A Warning (flashing codes like FAN for cooling fan failure) notifies you of a problem but may allow the motor to continue running at a limited capacity.

Q: How do I reset a fault on the LS S100?

A: Once the cause is resolved, you can reset the drive by:

• Pressing the STOP/RESET key on the front keypad.
• Closing the digital input terminal assigned to the RST (Reset) function.
• Cycling the main input power (Wait until the display goes completely blank before turning it back on).

Q: Why does my drive show “HC” on the display?

A: HC stands for Hardware Command. This is not a fault; it indicates that the Safe Torque Off (STO) inputs are open. The drive is in a “Safe State” and will not move the motor until the safety circuit is closed.

Q: Where is the fault history located on the keypad?

A: Navigate to the PRT (Protection) group. Parameters PRT-10 through PRT-14 store the last 5 trips. Pressing the ‘Enter’ key on these parameters will show the frequency and current at the time of the error.