21Fault

Felicity inverter error 21 (F21)

Over current happen in charging mode

Also displayed as F21 on some models.

Fault — the 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 current happen in charging mode — Over current is detected while charging the battery.

Cause: While charging the battery, current through the charger stage exceeded its protection limit. The trip is raised by the internal charging circuit, so persistent recurrence indicates a charger-stage fault rather than a battery wiring problem.

How to fix it

Contact the repair center.

Source: IVPS-IVPM User Guide.pdf, p.17 · ivps3524p1g1-lv-ivps5048p1g1-lv-ivps7548p2g1-ivps10048p2g1-manual.pdf, p.24

IVCM1012 PRO

InverterFault

Also applies to:IVCM2024 PROIVCM3024 PRO

What it means

OP current sensor failed — OP (output) current sensor failed.

Cause: The output current sensor has failed, so the inverter can no longer measure its output current reliably. This is an internal component fault.

How to fix it

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

Source: ICM.pdf, p.13

IVGM5KL-P1G1

InverterFault

Also applies to:IVGM6KL-P1G1IVGM7K6L-P1G1IVGM8KL-P1G1

What it means

BMS communication Alarm — Abnormal communication between battery and inverter in non-SOC mode, check battery and inverter wiring.

Cause: Communication has been lost between the inverter and a peripheral device — typically a battery BMS, smart meter, or external monitoring dongle.

How to fix it

Check battery and inverter wiring.

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

T-REX-3KLP1G01

InverterFault

Also applies to:T-REX-3K6LP1G01T-REX-4KLP1G01T-REX-4K6LP1G01T-REX-5KLP1G01T-REX-6KLP1G01T-REX-10KHP3G01

What it means

OP current sensor failed — Output current sensor failed.

Cause: The output current sensor returned an out-of-range or implausible reading, so the control board can no longer trust its output-current measurement.

How to fix it

Output current sensor failed.

Source: t-rex-3-3.6-4.6-5-6klp1g01-user-guide-english.pdf, p.38 · T-REX-10KHP3G01-Inverter-User-Guide.pdf, p.28

IVEM 6048

InverterFault

Also applies to:IVEM6048IVEM8048-IIIVEM12048-IIIVEM 8K-12K Series IIIVEM8048-LVIVEM8048

What it means

The inner temperature over

Cause: The inner temperature 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 · IVEM8K-12K-II_compressed.pdf, p.44 · FelicitySolar IVEM8048-LV Single Phase Hybrid Inverter User Guide.pdf, p.38

T-REX-10KLP3G01

InverterFault

What it means

OP current sensor failed — Output current sensor failed.

Cause: Output current sensor failed.

How to fix it

Output current sensor failed.

Source: t-rex-10klp3g01-inverter-user-guide-english.pdf, p.28

T-REX-50KHP3G01

InverterFault

What it means

Battery 2 software overcurrent fault — Battery 2 current is too large, check the battery charge and discharge power.

Cause: The control firmware measured battery 2 current above the protection limit — charge or discharge power beyond what that battery channel is rated for.

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-25-50khp3g01-user-guide-en.pdf, p.46

Apollo-5KLP1G01-MX

Energy storage systemCritical

Also applies to:Apollo-5KLP1G01-M1Apollo-5KLP1G01-M2Apollo-4K6LP1G01-MXApollo-4K6LP1G01-M1Apollo-4K6LP1G01-M2

What it means

OP current sensor failed — Output current sensor failed.

Cause: Output current sensor failed.

How to fix it

Output current sensor failed.

Source: t-rex-5klp1g01-t-rex-6klp1g01-datasheet-en.pdf, p.43

LUX-S-1600LG01

BatteryFault

What it means

PV Mos Short — Fault event: PV input MOSFET short-circuit fault detected.

Cause: A fault has been detected in the PV input stage — usually a short, ground fault, or isolation failure between the PV array and the inverter chassis. Wet connectors, damaged cable insulation, or moisture in a junction box are common causes.

How to fix it

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

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

Frequently asked questions

What does error 21 mean on a Felicity inverter?

It depends on the model — 13 devices use code 21. On the IVPS/IVPM Series it means: Over current happen in charging mode. The card for each model on this page gives its exact meaning and fix.

Is error 21 a fault or a warning?

21 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 21?

Contact the repair center. The exact steps for each affected model are listed on this page.

Related error codes

Other codes on the IVPS/IVPM Series

All IVPS/IVPM Series codes All IVPS3524P1G1-LV codes

Other codes on the IVCM1012 PRO

All IVCM1012 PRO codes

Other codes on the IVGM5KL-P1G1

All IVGM5KL-P1G1 codes

Other codes on the T-REX-3KLP1G01

All T-REX-3KLP1G01 codes All T-REX-10KHP3G01 codes

Other codes on the IVEM 6048

All IVEM 6048 codes All IVEM8048-II codes All IVEM8048-LV codes

Other codes on the T-REX-10KLP3G01

All T-REX-10KLP3G01 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.