What does error 78 mean on a Felicity inverter?

It depends on the model — 2 devices use code 78. On the IVGM5KL-P1G1 it means: Grid wrong Connect to buckup. The card for each model on this page gives its exact meaning and fix.

How do I clear or fix error 78?

1. Check whether Backup cables are firmly and correctly connected; 2. The exact steps for each affected model are listed on this page.

Felicity inverter error 78 (F78)

Grid wrong Connect to buckup

Also displayed as F78 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:

IVGM5KL-P1G1

InverterFault

Also applies to:IVGM6KL-P1G1IVGM7K6L-P1G1IVGM8KL-P1G1

What it means

Grid wrong Connect to buckup — Grid is incorrectly connected to backup port.

Cause: Grid voltage was detected on the backup (load) port — utility wiring has been landed on the backup terminals instead of the grid port.

How to fix it

Check whether Backup cables are firmly and correctly connected
Restart the system 2~3 times
Seek help from us, if can not go back to normal state.

Source: Felicitysolar IVGM Series Hybrid inverter Instruction Manual.pdf, p.55

T-REX-50KHP3G01

InverterFault

What it means

BAT1 Insulation Impedance fault — Battery 1 insulation is abnormal.

Cause: The insulation between the battery 1 circuit and ground measured below the safe threshold — damaged cable insulation or moisture in that battery's wiring.

How to fix it

Power down the inverter, wait 5 minutes for capacitors to discharge, then restart.
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.48

Frequently asked questions

What does error 78 mean on a Felicity inverter?: It depends on the model — 2 devices use code 78. On the IVGM5KL-P1G1 it means: Grid wrong Connect to buckup. The card for each model on this page gives its exact meaning and fix.
Is error 78 a fault or a warning?: 78 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 78?: 1. Check whether Backup cables are firmly and correctly connected; 2. The exact steps for each affected model are listed on this page.

Related error codes

Other codes on the IVGM5KL-P1G1

All IVGM5KL-P1G1 codes

Other codes on the T-REX-50KHP3G01

All T-REX-50KHP3G01 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.