Error FA 306

Safety precautions:

1. If you smell gas, evacuate the property immediately, do not operate electrical switches, and call the gas emergency number and an engineer. If a carbon monoxide alarm is sounding, evacuate and call emergency services. 2. Isolate electrical power to the boiler before opening panels — only qualified persons should remove covers. 3. Never attempt to dismantle or adjust gas valves, burner assemblies or replace internal components unless you are a Gas Safe registered engineer.

Initial homeowner checks (safe, non-invasive):

1. Note the exact error code and sequence (take a photo of the display). Does FA 306 appear immediately or after a few ignition attempts? 2. Perform a boiler reset: follow the boiler manual reset procedure (hold the reset button for the time specified). If the fault clears and does not return, monitor the boiler — if it reappears, further investigation is needed. 3. Check the basic supply: ensure the boiler has power and the gas supply to the property is on (check other gas appliances). 4. Check for obvious signs of water ingress or condensation around the boiler enclosure or flue termination and ensure the external flue terminal is not blocked. 5. Do not open the boiler or touch internal wiring or components.

What a Gas Safe engineer will check and do (diagnostic and fix steps):

1. Record fault history from the boiler service menu and inspect error logs. 2. Visual inspection: open the boiler and inspect the ionisation (flame) probe/electrode and its lead for damage, corrosion, carbon build-up or moisture. Check connector condition and secure seating. 3. Clean or replace the ionisation electrode if contaminated. Replace the ionisation lead if damaged or suspect (leads can fail or have high leakage). 4. Measure flame/ionisation current with appropriate diagnostic tools while attempting ignition (engineer measures microamp-level flame rectification current). Verify the probe is producing the correct signal only when flame is present. 5. Check earthing/ground continuity and bonding. Poor earth or stray conductive paths can give false ionisation readings. 6. Inspect the air-to-gas ratio control (air shutter / ratio valve) and its actuator for correct movement; if the valve is sticking or the actuator is faulty it can alter combustion and the control logic may react incorrectly. Replace if faulty. 7. Inspect burner and electrode alignment and condition; correct positioning is important for stable flame detection. 8. Inspect wiring between probe, gas valve and control PCB for shorts, chafing or moisture. Repair or replace suspect wiring/connectors. 9. If all sensors and wiring check out, test the PCB flame detection circuitry and relays; replace the PCB if a board fault is identified. 10. After any repairs, run full ignition and combustion checks, confirm safe operation, clear fault codes, and complete manufacturer-specified tests and documentation.

When to call a professional:

- If the FA 306 code persists after a reset, if you are uncomfortable performing the basic checks above, or if any internal inspection or repair is required, call a Gas Safe registered heating engineer. Because this fault involves flame detection and gas control, diagnosis and repair should be carried out only by qualified personnel.

Other practical notes:

- Keep a record of when the fault occurs (cold start, after running, intermittent) — this helps diagnosis. - Avoid repeatedly resetting the boiler as this can mask progressive faults and is not a substitute for a proper repair. - If you suspect water or condensate is reaching the flame probe (e.g., after heavy rain or flue issues), mention this to the engineer as it can cause intermittent ionisation readings.