Verified boiler fault code

Alpha 02 Fault Code (E-Tec 28 and 33)

Overheat boiler lockout.

Safety disclaimer

Boiler repair help from Aza & Sons Services

Fault code summary

Manufacturer
Alpha
Fault code
02
Fault type
Overheating, Circulation, Safety lockout
Severity
high
Reset
Not specified
Applicable models
E-Tec 28, E-Tec 33

Quick answer

Overheat boiler lockout.

What does this fault code mean?

Overheat boiler lockout.

Common causes

  • Pump or restricted-flow problem.
  • Blocked heat exchanger.
  • Air in heat exchanger.
  • External valves/circuit issue.

Symptoms

  • The boiler locks out on overheat.

What can the homeowner safely check?

This information was not provided in the verified manufacturer source.

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

  • Investigate circulation, heat exchanger, air and external valves/circuit.

Applicable boiler models

Related fault codes

Manufacturer documentation

Alpha E-Tec installation and servicing instructions

02 | Overheat boiler lock out | Overheat sensor has activated | Pump or restricted flow problem; blocked heat exchanger; air in heat exchanger; external valves/circuit

Last verified

2026-09-12

Frequently asked questions

What does Alpha 02 mean?

Overheat boiler lockout.