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State 109

Fronius Solar Inverter

Severity: Moderate

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

Fronius State 109 — Grid Frequency Too High

What Does This Error Mean?

State 109 on a Fronius inverter means grid frequency is above the country's allowed maximum (typically 50.5 Hz in EU, 60.5 Hz in NA). The inverter disconnects per grid code. Most events are transient — recurring State 109 indicates a generator-fed installation or weak local grid.

Affected Models

  • Fronius Primo
  • Fronius Symo
  • Fronius Galvo
  • Fronius IG Plus
  • Fronius Tauro

Common Causes

  • Brief grid frequency excursion from major fault elsewhere
  • Site fed by a small generator with poor frequency regulation
  • Microgrid or island system with weak frequency control
  • Unusually low grid load causing frequency rise
  • Inverter measurement calibration drift (rare)

How to Fix It

  1. Confirm whether State 109 is recurring.

    Check Solar.web history. Single events from grid faults clear automatically. Repeat State 109 daily indicates a chronic grid stability issue.

  2. Note the time of day.

    State 109 at midnight or weekends suggests grid instability under low load. State 109 at peak solar hours suggests rare frequency rise from PV oversupply. Pattern helps narrow the cause.

  3. Check generator-fed sites.

    If your site is on a generator (off-grid or backup), the generator's frequency regulation may be inadequate for the inverter. Most Fronius inverters need a stable grid.

  4. Contact utility for grid investigation.

    Recurring State 109 with utility supply indicates grid issues. Document times and provide them to the utility. They may identify upstream issues affecting your area.

  5. Ask installer about wider frequency settings.

    Some jurisdictions allow installers to widen frequency limits within regulatory tolerance. This is a workaround. The grid issue should still be addressed.

Frequently Asked Questions

Will State 109 affect my Fronius's annual production?

Brief State 109 events (a few seconds) cause minimal lost production. Frequent State 109 (multiple times per day, several minutes each) can lose 5–15% of expected production. Solar.web reports show the impact precisely.

Can I eliminate State 109 with software settings alone?

Software changes alone cannot fix a real grid frequency issue. Wider frequency limits via the installer mask the symptom but the underlying weak-grid issue should still be addressed by the utility for safety and reliability.