A02 Boiler Fault Code: What It Means on Every Brand

The A02 fault code appears on 3 brands — Andrews, Ferroli and Vokera — and it does not mean the same thing on each. The same two or three characters can signal a pressure problem on one boiler and an ignition fault on another, so identify your brand first and use the table below to jump to the right page.

Up to: Lockout — engineer likely 3 brands use this code Meaning differs by brand

Which brand is your boiler?

The brand is printed on the front casing. Tap your brand for the full causes, fixes and repair costs.

Brand	What A02 means	Severity	DIY?
AAndrews	The A02 fault code means the boiler's control system is detecting a flame signal even though the burner has been commanded to switch off. Full guide →	Lockout — engineer likely	No
FFerroli	The A02 code is a hard lockout fault on Ferroli boilers, meaning the boiler has shut itself down and will not restart until you manually reset it. Full guide →	Lockout — engineer likely	No
VVokera	The A02 code on a Vokera boiler means the safety limit thermostat has triggered a protective shutdown. Full guide →	Engineer may be needed	Some checks

A02 brand by brand

Andrews A02

The A02 fault code means the boiler's control system is detecting a flame signal even though the burner has been commanded to switch off. This is commonly referred to as a 'spurious' or 'false flame' signal — the ionisation circuit is reporting a flame present when there should be none. Because the boiler cannot safely continue operating in this state, it locks out and requires a manual reset. The two principal causes identified for this code are an ionisation electrode fault (including its wiring and ignition cable) and a PCB (control board) anomaly. Andrews Water Heaters are predominantly commercial and industrial gas-fired appliances, so this fault should always be attended to by a Gas Safe registered engineer familiar with commercial equipment.

Causes, fixes & costs for Andrews A02 → · All Andrews codes

Ferroli A02

The A02 code is a hard lockout fault on Ferroli boilers, meaning the boiler has shut itself down and will not restart until you manually reset it. It indicates that the flame sensor (ionisation electrode) is reporting a flame signal at a point when the burner has not been instructed to fire. Because an unexpected flame signal is a genuine safety concern, Ferroli's control system immediately locks the boiler out. This is quite different from a simple ignition failure — the boiler isn't struggling to light; it believes a flame exists when it shouldn't. Codes beginning with 'A' on Ferroli boilers are always hard lockouts of this type, whereas 'F' prefix codes are softer blocking faults that can sometimes clear on their own.

Causes, fixes & costs for Ferroli A02 → · All Ferroli codes

Vokera A02

The A02 code on a Vokera boiler means the safety limit thermostat has triggered a protective shutdown. This thermostat continuously monitors internal water temperature, and when it senses that the boiler is running hotter than it safely should, it cuts operation to prevent damage. The result is a loss of both heating and hot water until the underlying cause is identified and resolved. On newer Vokera Evolve models, the same issue may appear as code E020 rather than A02.

Causes, fixes & costs for Vokera A02 → · All Vokera codes

Frequently asked questions

Is the A02 fault code the same on every boiler?

No. A02 means different things on different brands — see the table above. Always identify your boiler's brand (it is printed on the front casing) before acting on any advice about the code.

Can I fix a A02 fault myself?

On some brands there are safe homeowner checks first — typically system pressure, the condensate pipe in cold weather, and a single reset. The underlying repair usually needs a registered engineer. Never open the boiler casing yourself.

Who should I call about a A02 fault?

For gas boilers, a Gas Safe registered engineer — it is a legal requirement for any work on the appliance. If you smell gas at any point, leave the property and call the National Gas Emergency line on 0800 111 999.

General guidance only — not a substitute for professional advice, and not certified by a registered engineer. Any work on a gas appliance must be carried out by a Gas Safe registered engineer. If you smell gas, call 0800 111 999.