Ferroli F05 Fault Code (i25 / i29)

Safety disclaimer

Fault code summary

Manufacturer

Ferroli

Fault code

F05

Fault type

Fan, Flue, Electrical

Severity

temporary

Reset

Ferroli states that F faults reset automatically when the value returns to the normal range.

Applicable models

Ferroli i25, Ferroli i29

Quick answer

Air-pressure switch did not close within 20 seconds of fan activation.

What does this fault code mean?

Air-pressure switch did not close within 20 seconds of fan activation.

Common causes

• Air-pressure switch contact open.
• Pressure-switch wiring fault.
• Wrong baffle.
• Obstructed or incorrectly sized flue.
• Dirty exchanger.
• Faulty water circulation.

Symptoms

• The display flashes F05 and the boiler temporarily shuts down.

What can the homeowner safely check?

• Do not obstruct, dismantle or alter the flue; contact a qualified engineer.

Boiler reset information

Ferroli states that F faults reset automatically when the value returns to the normal range.

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

• Check air-pressure switch, fan, wiring, baffle, flue and circulation.

Applicable boiler models

• Ferroli i25
• Ferroli i29

Related fault codes

• A01 — i25 / i29

  No burner ignition.

  Read fault code
• A02 — i25 / i29

  Flame-present signal with the burner off.

  Read fault code
• A03 — i25 / i29

  Overtemperature protection intervention.

  Read fault code
• A06 — i25 / i29

  No flame after the ignition phase.

  Read fault code
• A09 — i25 / i29

  Gas-valve fault.

  Read fault code
• A15 — i25 / i29

  Air-pressure-switch fault F05 generated five times in the last 24 hours.

  Read fault code
• A16 — i25 / i29

  Gas-valve fault.

  Read fault code
• A23 — i25 / i29

  Card parameter fault.

  Read fault code

Manufacturer documentation

Table 9: F05 — Air pressure switch fails to close contacts within 20 sec. of fan activation; table lists switch, wiring, baffle, flue, exchanger and circulation causes.

Last verified

2026-09-12

Frequently asked questions