18Fault

Felicity inverter error 18 (F18)

Over temperature

Also displayed as F18 on some models.

Faultthe inverter cuts its output and the red LED stays solid until the fault is cleared.

The exact meaning depends on your model:

IVPS/IVPM Series

InverterFault

Also applies to:IVPS2512IVPS2524IVPS3524IVPS5024IVPS5048IVPS7548IVPS-7548IVPS10048+9

What it means

Over temperatureThe internal temperature of the inverter is too high.

Cause: The inverter has overheated.

How to fix it

  1. Turn off the inverter and let it cool down.
  2. After the temperature is back to normal you can use it again.

Source: IVPS-IVPM User Guide.pdf, p.17 · IVPS3524P1G1-LV IVPS5048P1G1-LV IVPS7548P2G1 IVPS10048P2G1 User Guide - EN.pdf, p.24

IVGM5KL-P1G1

InverterFault

Also applies to:IVGM6KL-P1G1IVGM7K6L-P1G1IVGM8KL-P1G1

What it means

Battery Under Voltage AlarmBattery voltage is too low, the battery should be charged.

Cause: Battery voltage has fallen to the low-voltage alarm threshold — the pack is nearly depleted and needs charging before the inverter cuts off discharge.

How to fix it

  1. Restart the system 2~3 times
  2. If the fault still exists, please contact us for help.

Source: Felicitysolar IVGM Series Hybrid inverter Instruction Manual.pdf, p.51 · Felicitysolar IVGM Series Hybrid inverter Instruction Manual.pdf, p.53

IVEM 6048

InverterFault

Also applies to:IVEM6048

What it means

Over temperature happen at PV circuit

Cause: The temperature of internal PV converter component is over the limitation.

How to fix it

Check whether the air flow of the unit is blocked or whether the ambient temperature is too high.

Source: felicitysolar IVEM 6048 Solar Inverter User Guide.pdf, p.37

IVEM8048-II

InverterFault

Also applies to:IVEM12048-IIIVEM 8K-12K Series IIIVEM8048-LVIVEM8048

What it means

Over temperature happen at PV circuit

Cause: The temperature of internal PV component is over the limitation.

How to fix it

Check whether the air flow of the unit is blocked or whether the ambient temperature is too high.

Source: IVEM8K-12K-II_compressed.pdf, p.43 · FelicitySolar IVEM8048-LV Single Phase Hybrid Inverter User Guide.pdf, p.38

T-REX-10KLP3G01

InverterFault

What it means

The output overcurrent is abnormal

Cause: The inverter's output current ran above the protection limit — an overload or surge on the connected loads, or a fault in the output stage's current control.

How to fix it

Restart the unit, if the error persists, contact the repair center.

Source: T-REX-10KLP3G01-Inverter-User-Guide.pdf, p.28

T-REX-50KHP3G01

InverterFault

What it means

Battery 1 Undervoltage faultBattery 1 voltage is too low, the battery should be charged.

Cause: Battery 1 voltage has fallen below the permitted range — the pack is deeply discharged and must be charged before normal operation resumes.

How to fix it

  1. Power down the inverter, wait 5 minutes for capacitors to discharge, then restart.
  2. If the fault recurs immediately or repeatedly, record the exact code and contact your installer or the manufacturer's service line.

Source: T-REX-50KHP3G01-user-manual-.pdf, p.46

LUX-S-1600LG01

BatteryFault

What it means

SampSensor is errorFault event: sampling sensor (current/voltage sensing circuit) error.

Cause: The current/voltage sampling sensor returned abnormal values — an internal sensing-circuit fault.

How to fix it

  1. Restart the unit.
  2. If the error persists, contact the repair center.

Source: LUX-S-1600LG01.pdf, p.22

LUX-Y-48100HG01

BatteryCritical

Also applies to:LUX-Y-48100HCG01LUX-Y-48100HMG01LUX-Y-48100HR13G01LUX-Y-48100HR9G01

What it means

Relay Adhesion FaultMain relay contacts have welded/stuck (relay adhesion).

Cause: A safety relay inside the inverter has failed self-test or is stuck. The inverter is designed to refuse grid connection in this state, so this is not an issue you can clear with restart cycles.

How to fix it

Restart, if the fault still exists, contact our engineer.

Source: LUX-Y-48100HG01-Lithium-Battery-User-Guide.pdf, p.20

LUX-Y-48100HG01MN

BatteryFault

What it means

Relay Adhesion Fault

Cause: A safety relay inside the inverter has failed self-test or is stuck. The inverter is designed to refuse grid connection in this state, so this is not an issue you can clear with restart cycles.

How to fix it

  1. This requires service — the relay assembly is not user-replaceable.
  2. Record the exact fault code and contact your installer or the manufacturer's service line.
  3. Do not bypass any safety interlock.

Source: LUX-Y-48100HG01MN User manual 358-S010025-03 0325(V2.0).pdf, p.27

Frequently asked questions

What does error 18 mean on a Felicity inverter?
It depends on the model — 11 devices use code 18. On the IVPS/IVPM Series it means: Over temperature. The card for each model on this page gives its exact meaning and fix.
Is error 18 a fault or a warning?
18 is a fault code: the inverter cuts its output and the red LED stays solid until it is cleared.
How do I clear or fix error 18?
Turn off the inverter and let it cool down. After the temperature is back to normal you can use it again. The exact steps for each affected model are listed on this page.

Related error codes

Prefer the full written guide? Read the complete Felicity inverter error-code guide

Compiled from official Felicity user manuals. Always consult your device manual and a qualified technician before performing repairs.