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State 103

Fronius Solar Inverter

Severity: Moderate

Source: OnlyErrorCodes.com — Every error code. One place.

Fronius Inverter State 103 — AC Voltage Too Low

What Does This Error Mean?

Fronius State 103 means the AC grid voltage at the inverter terminals has dropped below the minimum permitted level. The inverter disconnects automatically to comply with grid safety standards. It will reconnect automatically once the grid voltage returns to a normal level.

Affected Models

  • Fronius Primo
  • Fronius Symo
  • Fronius Galvo
  • Fronius SnapINverter Series
  • Fronius GEN24 Plus

Common Causes

  • Grid voltage sag during heavy local demand — large motors, air conditioning starting up
  • Utility supply issue in your street or neighbourhood
  • Long or undersized cable run from the meter board to the inverter causing voltage drop under load
  • Loose connection in the AC wiring from the inverter to the switchboard
  • Inverter's minimum voltage threshold set too high relative to your local grid voltage

How to Fix It

  1. Wait for the inverter to reconnect automatically.

    State 103 clears automatically once grid voltage rises back to the minimum threshold. Most events last only a few seconds to a few minutes. Check whether production resumed on Solar.web or the Fronius display.

  2. Check Solar.web for frequency of State 103 events.

    Log in to Solar.web (solarweb.com) and check the Events log. Note what time of day State 103 events occur — events at times of high local demand (early morning in summer, late afternoon) suggest a grid capacity issue rather than a wiring fault.

  3. Measure the supply voltage at the inverter input.

    With a multimeter at the inverter's AC terminals (or at the solar isolator outlet), measure the voltage during normal operation. For a 230V single-phase system, the voltage should be between 207V and 253V. Consistently below 215V suggests a wiring or grid issue.

  4. Check the AC cable size and length from switchboard to inverter.

    A 5 kW inverter on a 2.5 mm² cable over 10 metres will experience a significant voltage drop under full production. Your installer should verify the cable is correctly sized for the inverter power and cable run length.

  5. Report persistent low grid voltage to your electricity provider.

    If the measured voltage at your meter is consistently below 207V (for a 230V supply), your electricity provider is obligated to investigate and correct it. Low grid voltage can also damage appliances.

When to Call a Professional

If State 103 occurs frequently or keeps the system offline for hours each day, have a licensed electrician measure the supply voltage at the inverter terminals. An undersized cable or loose connection can cause this problem.

Frequently Asked Questions

What is the difference between Fronius State 102 and State 103?

State 102 means AC voltage is too high — the inverter is trimming it. State 103 means AC voltage is too low. Both cause the inverter to disconnect automatically and reconnect when voltage returns to the permitted range.

Can I adjust the voltage thresholds on my Fronius inverter?

Yes, but only a licensed electrician or accredited solar installer can adjust the grid parameters. Changes must comply with local grid standards and the utility's requirements. Incorrect settings can void warranty or cause grid compliance issues.