Critical

F42

Relay check failure.

7 Devices that report this code

What does the F42 error code mean?

F42 on a Felicity unit indicates: Relay check failure.. It is a critical-severity event that can appear on 7 different devices in the Felicity catalog. The same code may have slightly different recommended fixes depending on the device — the per-device sections below show the exact wording from each device's official manual.

This is a critical-severity code

Critical codes trip the unit offline immediately. They typically indicate hardware failure (short-circuit, IGBT, BMS) or an unsafe operating condition. Do not bypass the fault — note the code and contact authorized service.

What triggers this code

F42 is triggered when the unit's protection or monitoring logic detects the specific condition described above. The exact trigger depends on the device — see the per-device sections for the official manual entry for each.

Apollo-5KLP1G01-MXEnergy storage system↗ view on device
F42Relay check failure.Critical
Description

Relay self-check failure.

Cause

Relay check failure.

Recommended fix

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

Source:Apollo-5KLP1G01-All-in-one-ESS-User-Guide.pdf · page 44
IVEM 6048Inverter↗ view on device
F42Synchronization data loss.Fault
Description

Fault: Synchronization data loss.

Cause

Communication cable connection issue between paralleled inverters.

Recommended fix

1. Check if communication cables are connected well and restart the inverter. 2. if the problem remains, please contact your installer.

Source:felicitysolar IVEM 6048 Solar Inverter User Guide.pdf · page 38
IVEM8048-IIInverter↗ view on device
F42Synchronization data loss.Fault
Description

Fault: Synchronization data loss.

Cause

Synchronization data loss in parallel communication.

Recommended fix

1. Check if communication cables are connected well and restart the inverter. 2. if the problem remains, please contact your installer.

Source:IVEM8K-12K-II_compressed.pdf · page 44
IVEM8048-LVInverter↗ view on device
F42Synchronization data loss.Fault
Description

Synchronization data loss.

Cause

Communication failure between paralleled inverters.

Recommended fix

1. Check if communication cables are connected well and restart the inverter. 2. if the problem remains, please contact your installer.

Source:FelicitySolar IVEM8048-LV Single Phase Hybrid Inverter User Guide.pdf · page 39
T-REX-10KHP3G01Inverter↗ view on device
F42Relay check failure.Fault
Description

Relay self-check failure.

Recommended fix

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

Source:T-REX-10KHP3G01-Inverter-User-Guide.pdf · page 29
T-REX-10KLP3G01Inverter↗ view on device
F42Relay check failure.Fault
Description

Relay check failure.

Recommended fix

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

Source:T-REX-10KLP3G01-Inverter-User-Guide.pdf · page 29
T-REX-50KHP3G01Inverter↗ view on device
F42Balanced Bridge Overcurrent Fault.Fault
Description

Balanced bridge current is too high, shutdown and restart.

Source:T-REX-50KHP3G01-user-manual-.pdf · page 47

Frequently asked about F42

What is the F42 error on Felicity?
F42 on a Felicity unit means: Relay check failure.. It can appear on 7 different devices in the Felicity catalog. The cause and recommended fix are listed for each device on this page.
Can I clear the F42 code myself?
It depends on the severity. Warning-level codes can usually be cleared by following the recommended fix. Fault and critical codes often require checking the source condition first; if the code returns immediately after restart, escalate to authorized service.
Is the F42 fix the same on every device?
The cause is consistent — it's the same protection logic. The exact fix wording can differ per device because each official manual addresses model-specific context (input ranges, parallel-config notes, firmware revisions). Use the per-device section that matches your unit.
Where does this information come from?
Every entry is sourced directly from the official Felicity user manual for the affected device. The "Source" line at the bottom of each device's section shows the manual filename and page number.

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