303 on a Fronius International GmbH Fronius SnapINverter: Power stage set overtemperature
Short answer
On a Fronius International GmbH inverter, 303 means: Power stage set overtemperature. The inverter keeps running with some functions stopped. An engineer is needed to fix the cause.
Reviewed 24 September 2026 · 1 source
What it means
The manual says: Power stage set overtemperature.
Part involved: power stage cooling.
When it shows: Class 3 status code.
Likely causes:
- Short-term interruption due to overtemperature; purge cooling-air openings and heat sink if necessary; rectified automatically; if recurring contact system engineer.
Is it safe?
| Does the inverter stop? | Partly |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The inverter keeps running with some functions stopped.
Resetting itself: yes.
Manual reset: Automatic when condition clears.
What you can check
- Read the state code on the inverter display or in Fronius Solar.web and note date/time for your installer.
- Check nothing is stacked against, covering or boxing in the inverter and that air can flow around it; keep the area clear.
- If recurring, contact installer.
What the engineer will check
- Clean cooling-air openings/heat sink/fan; check clearances and ambient temperature.
Who to ask for: Fronius-trained PV installer / Fronius Service Partner.
Certification: Qualified electrician (BS 7671; MCS-certified PV installer for work on the PV array/DC side).
What you might notice
Sources
- Fronius Primo 3.0-1 - 8.2-1 Operating Instructions (HTML) ↗ · 42,0410,2165 online edition · Reviewed 24 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 24 September 2026