Solar · Error codes
What is an Iso Fault on a Fox ESS inverter and is it dangerous?
Short answer
Iso Fault means the inverter measured low insulation between the solar panel wiring and earth, often from water ingress or damaged cable. It will not start exporting until the reading recovers. Fox advises waiting to see if it clears, then getting help (checked 24 September 2026). Do not touch DC cabling; an installer must insulation-test the strings.
Last checked 24 September 2026 · 1 source
In more detail
- Morning-only faults that clear as the day dries are typical of moisture.
- Persistent faults need string-by-string insulation resistance testing.
- The red LED lights for an earth-fault alarm (IEC 62109-2).
The facts, dated
- 01Fox H1 G2 manual links the earth-fault alarm to IEC 62109-2 clause 13.9 and a red LED.
manufacturer · UK · checked 24 September 2026 · fox-ess.com
Sources
Last checked: 24 September 2026