E4Fault

Felicity inverter error E4

Bus Volt Low

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

E-CHO-SI3KS2

InverterFault

Also applies to:E-CHO-SI5KS2E-CHO-SI8KS2

What it means

Bus Volt Low — DC bus voltage low.

Cause: Internal DC bus voltage has fallen below the inverter's minimum operating threshold. Common causes: PV string voltage too low (early morning, heavy shading, snow/sand cover), faulty MPPT tracker, or aging DC link capacitors.

How to fix it

  1. Check PV string open-circuit voltage in full sun.
  2. If below the inverter's minimum start-up Voc, you may have damaged panels, a broken string, or reverse-polarity wiring.
  3. If string voltage is normal, the fault is internal — power down the inverter, wait 5 minutes, and restart.
  4. Persistent faults require service.

Source: E-CHO-SI3KS2-Operation-Manual.pdf, p.16 · E-CHO-SI5KS2-Operation-Manual.pdf · E-CHO-SI8KS2-Operation-Manual.pdf

Frequently asked questions

What does error E4 mean on a Felicity inverter?
E4 means: Bus Volt Low. Internal DC bus voltage has fallen below the inverter's minimum operating threshold. Common causes: PV string voltage too low (early morning, heavy shading, snow/sand cover), faulty MPPT tracker, or aging DC link capacitors.
Is error E4 a fault or a warning?
E4 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 E4?
Check PV string open-circuit voltage in full sun. If below the inverter's minimum start-up Voc, you may have damaged panels, a broken string, or reverse-polarity wiring.

Related error codes

Other codes on the E-CHO-SI3KS2

All E-CHO-SI3KS2 codes All E-CHO-SI5KS2 codes All E-CHO-SI8KS2 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.