Verified boiler fault code
Ferroli A03 Fault Code (i25 / i29)
Overtemperature protection intervention.
Safety disclaimer
Fault code summary
- Manufacturer
- Ferroli
- Fault code
- A03
- Fault type
- Overheating, Circulation, Safety lockout
- Severity
- lockout
- Reset
- Ferroli states that A faults cause permanent shutdown and may be restored with RESET only after the fault is eliminated.
- Applicable models
- Ferroli i25, Ferroli i29
Quick answer
Overtemperature protection intervention.
What does this fault code mean?
Overtemperature protection intervention.
Common causes
- Heating sensor damaged.
- No water circulation.
- Air in the system.
- Safety thermostat intervention.
Symptoms
- The display flashes A03 and the boiler permanently shuts down.
What can the homeowner safely check?
- Read the system pressure and contact the installer if the code persists.
Boiler reset information
Ferroli states that A faults cause permanent shutdown and may be restored with RESET only after the fault is eliminated.
When should I call an engineer?
Contact a suitably qualified heating engineer when the fault persists, the boiler locks out, or the manufacturer instructions do not resolve it. For gas appliance work in the UK, use a Gas Safe registered engineer.
Engineer diagnosis
- Investigate heating sensor, pump/circulation, air and safety thermostat.
Applicable boiler models
Related fault codes
- A01 — i25 / i29
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Read fault code
Manufacturer documentation
i25 / i29 Instructions for use, installation and maintenanceTable 9: A03 — Overtemperature protection intervention; causes include sensor, circulation, air and safety thermostat.
Last verified
2026-09-12
Frequently asked questions
What does Ferroli A03 mean?
Overtemperature protection intervention.
Can I reset a Ferroli A03 fault?
Ferroli states that A faults cause permanent shutdown and may be restored with RESET only after the fault is eliminated.