This fault can involve incomplete combustion and carbon monoxide.
If anyone in the property feels sick, dizzy or drowsy, or you can smell gas: open the windows, leave the building, and do not switch anything on or off. Then call the National Gas Emergency Service.
0800 111 999Ferroli A02 fault codewhat it means and how to fix it
A flame is being detected while the burner should be off. Switch the appliance off and get a Gas Safe engineer to it.
Stop — this needs an engineer
Get a Gas Safe registered engineer to look at your Ferroli A02
We do not pass enquiries to a repair firm, so there is no form here. Find a Gas Safe registered engineer through the Gas Safe Register, and ask to see their registration card when they arrive — it is the register, not the van, that tells you they are qualified.
What A02 means
A02 is flame detected with the burner off. Ferroli attribute it to a defective ionisation electrode or a defective main board, and in the majority of cases that is what it turns out to be — the sensing circuit is reporting a flame that is not there. But the code cannot distinguish a false reading from a true one, and the true version means gas is still burning after the valve was told to close, which is a gas valve that is passing. That is a genuine safety fault rather than an inconvenience.
Since neither you nor the appliance can tell which of the two you have without test equipment, the correct response is to assume the more serious one until an engineer proves otherwise. This is one of the few boiler codes where the right first action is to isolate the appliance rather than to reset it and see what happens.
What causes it
| Cause | What is actually happening | How likely |
|---|---|---|
| Ionisation electrode defective | Named first in the Ferroli manual. Contamination or a breakdown in the electrode wiring produces a signal that mimics a flame. The most common cause and the benign one. | Common |
| Gas valve passing | The valve is not sealing when closed and gas continues to reach the burner. Less common, and the reason this code is handled as urgent. | Occasional |
| Damp tracking across the electrode lead | Moisture from a leak inside the case, or condensation in a cold garage installation, creating a conductive path. | Occasional |
| Main board defective | Ferroli list checking the PCB. The flame amplifier stage misreads its own input. | Rare |
Can you fix it yourself?
Stop — this needs an engineer
What it costs to fix
Typical repair cost
£110–£380
An ionisation electrode is £110 to £190 fitted. A gas valve is £240 to £320. Expect a diagnostic charge on top, since separating the two requires a flue gas analyser.
Typical UK prices including parts and labour, updated September 2026. Your quote may differ.
Own this appliance and had this code? . Nothing is published until a person has read it.
Related Ferroli fault codes
- A01Get it checkedThe burner failed to light and the appliance has locked out. Ferroli list a blocked siphon as a cause, which is worth checking early.Related: ignition and gas supply
- F37Usually simple to fixSystem water pressure is outside the correct range. Because this is an F code it clears by itself once you top the system back up.Related: same brand
- A03Get it checkedHigh limit protection has operated. Ferroli point at circulation and at the flow sensor position, and both are worth checking.Related: same brand
- A05Get it checkedThe fan tachometer signal has been missing for an hour or more. The appliance has stopped and needs an engineer.Related: same brand
- F07Get it checkedFlue gas temperature has stayed above 95°C for more than two minutes. Three of these in a day becomes a permanent A04 lockout.Related: same brand
Own a Ferroli boiler? Save it and its codes come first next time.
Related guides
Common questions about Ferroli A02
Should I press R to see whether it clears?
No, and this is the one Ferroli code where that instinct is wrong. With every other A code, trying the reset is a reasonable first move. Here the appliance has latched off precisely so it cannot resume while nobody is watching, and overriding that is the only genuinely unsafe thing you can do from the front panel. Switch it off at the fused spur and leave it.
What should I say when I book an engineer?
Quote it as A02 and use the phrase "flame detected with the burner off". That is the exact wording in the Ferroli manual, and an engineer who knows the brand will arrive with an analyser and the right two parts in the van rather than making a diagnostic visit first.
Why does Ferroli make this an A code rather than an F code?
Because F codes are designed to clear themselves once the reading returns to normal, and a flame that should not be there is not a condition anyone wants the appliance deciding is fine again. The permanent latch is deliberate and it is the manufacturer telling you how seriously to take it.
The manual blames the ionising electrode. Can I just get that changed?
You can ask, but a competent engineer will want to prove the gas valve is sealing before they call it. Ferroli list the electrode first because it is the likelier of the two, not because the other one can be skipped.
Technical review
Not reviewed by an engineer
No engineer has read this page. Severity follows what the manufacturer publishes, and we would rather tell you that than let a byline imply a sign-off.
Sources and how we verified this
We establish the facts from the sources below and then write the explanation ourselves. We do not copy manufacturer wording and we do not host their manuals.
- Manufacturer technical and service documentation
- Trade body guidance
This page has not been reviewed by an engineer, and we would rather tell you that than imply otherwise. The severity rating follows what the manufacturer publishes: where they say isolate the appliance and call someone, so do we.