Alpha 27 Fault Code (Evoke 28 and 33)

Safety disclaimer

Fault code summary

Manufacturer

Alpha

Fault code

27

Fault type

Overheating, Circulation, Central heating

Severity

high

Reset

Not specified

Applicable models

Evoke 28, Evoke 33

Quick answer

Primary circuit overheat.

What does this fault code mean?

Primary circuit overheat.

Common causes

• Insufficient circulation in the primary circuit.
• Air in heat exchanger.
• Closed isolation/system valves.
• Pump wiring, seized/blocked or failed pump.

Symptoms

• The boiler may overheat and stop.

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

• Assess primary circulation, valves, heat exchanger, pump power and pump condition.

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
• 03 — Evoke 28 and 33

  High flue temperature.

  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

Manufacturer documentation

27 | Primary circuit overheat | Insufficient circulation in primary circuit causing overheating | Air in heat exchanger; isolation/system valves closed; wiring/power to pump; pump seized/blocked; pump failed

Last verified

2026-09-12

Frequently asked questions