Alpha 03 Fault Code (Evoke 28 and 33)

Safety disclaimer

Fault code summary

Manufacturer

Alpha

Fault code

03

Fault type

Flue, Overheating, Safety lockout

Severity

high

Reset

Not specified

Applicable models

Evoke 28, Evoke 33

Quick answer

High flue temperature.

What does this fault code mean?

High flue temperature.

Common causes

• Restricted primary flow.
• Heat-exchanger air-flow blockage.
• Flue restriction.
• Flue sensor fault.
• Air in primary heat exchanger.

Symptoms

• Flue sensor intervention because flue temperature is too high.

What can the homeowner safely check?

• Do not dismantle or obstruct the flue; arrange qualified diagnosis.

Boiler reset information

Reset information was not provided in the verified manufacturer source. Do not repeatedly reset an unresolved fault.

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

• Assess flue, flue sensor, primary flow and heat-exchanger air path.

Applicable boiler models

• Evoke 28
• Evoke 33

Related fault codes

• 01 — Evoke 28 and 33

  Ignition failure; flame not detected during the ignition sequence.

  Read fault code
• 02 — Evoke 28 and 33

  Overheat boiler lockout.

  Read fault code
• 04 — Evoke 28 and 33

  Gas-valve electrical connection fault.

  Read fault code
• 05 — Evoke 28 and 33

  CH flow sensor fault.

  Read fault code
• 06 — Evoke 28 and 33

  DHW sensor fault.

  Read fault code
• 08 — Evoke 28 and 33

  Maximum number of resets reached (five).

  Read fault code
• 10 — Evoke 28 and 33

  Primary system pressure low.

  Read fault code
• 16 — Evoke 28 and 33

  Fan fault.

  Read fault code

Manufacturer documentation

03 | High flue temperature | Flue sensor intervention (flue temperature too high) | Blocked or restricted primary flow; heat exchanger air flow blocked; flue restriction; flue sensor fault; air in primary heat exchanger

Last verified

2026-09-12

Frequently asked questions