Alpha 03 Fault Code (E-Tec 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

E-Tec 28, E-Tec 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

• E-Tec 28
• E-Tec 33

Related fault codes

• 01 — E-Tec 28 and 33

  Ignition failure; flame not detected during the ignition sequence.

  Read fault code
• 02 — E-Tec 28 and 33

  Overheat boiler lockout.

  Read fault code
• 04 — E-Tec 28 and 33

  Gas-valve electrical connection fault.

  Read fault code
• 05 — E-Tec 28 and 33

  CH flow sensor fault.

  Read fault code
• 06 — E-Tec 28 and 33

  DHW sensor fault.

  Read fault code
• 08 — E-Tec 28 and 33

  Maximum number of resets reached (five).

  Read fault code
• 10 — E-Tec 28 and 33

  Primary system pressure low.

  Read fault code
• 16 — E-Tec 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