Vokera water heater shows code 02, burner shuts down shortly after ignition or fails to light, possible overheat indication

Safety first: Switch off power to the heater and allow it to cool completely before touching any pipework. Do not bypass safety thermostats.

User-level checks:

• Reset the appliance: Use the reset control as per the manual. If the code reappears quickly, stop using the heater.
• Check system pressure (for sealed systems): On combination or system units, ensure the pressure gauge is typically between 1.0–1.5 bar when cold. If low, top up via the filling loop following the manufacturer’s instructions and bleed radiators if applicable.
• Ensure all hot water outlets are open properly: A severely restricted outlet can cause local overheating.

Technician checks:

• Inspect and clean the primary heat exchanger for scale and sludge; power-flush or chemically clean if necessary.
• Test the overheat thermostat / safety temperature sensor for correct operation and replace if faulty.
• Verify operation of the circulation pump (on combi/system models) and ensure there are no airlocks in the primary circuit.
• Check for blocked filters or strainers in the return line.

Because this fault involves overheating and safety devices, any internal work should be carried out only by a qualified heating engineer.