Error 305 0

Safety precautions:

- If you are unsure or uncomfortable at any point, stop and call a Gas Safe registered engineer. Do not attempt gas or internal electrical repairs.

- Before touching any boiler controls, make sure hands are dry and you have clear access. Do not block the flue or ventilations.

- If you smell gas, leave the property immediately and contact the gas emergency service; do not operate the boiler.

Initial checks a homeowner can do:

1. Check whether the house has hot water available from taps. If hot water is available and the boiler display shows 305 0, this is likely just anti-cycle following a DHW draw and can be left alone.

2. Note recent activity: was a large hot water draw (bath, washing machine, dishwasher) used in the last few minutes? Anti-cycle commonly follows significant DHW use.

3. Check timers, programmers, and room thermostat settings to ensure there is no conflicting demand setting. Confirm the boiler is set to provide DHW if required.

4. Check the boiler pressure gauge. If pressure is low (typically below 1 bar), top up to the manufacturer’s recommended pressure per the manual. Low system pressure can cause other issues, but it will not normally cause anti-cycle.

5. Observe the display for other codes. If 305 0 appears alone and the boiler otherwise behaves normally, it is informational.

Specific diagnostic and simple fixes to try:

1. Wait and observe: Anti-cycle is a timed wait. Leave the boiler alone for 5–15 minutes to see if it returns to normal operation. Many anti-cycle pauses are short.

2. Reset the boiler only if the unit is unresponsive or you suspect a stuck state. Follow the manual: either press and hold the reset button for 3 seconds or turn the temperature dial to the reset mark and hold for 3 seconds, then return settings. Do not reset if the display shows an EA or other warning error code (EA indicates a gas/ignition issue). After reset, observe whether 305 0 returns or other faults appear.

3. Check domestic hot water control and cylinder thermostat (if you have a separate cylinder): ensure the cylinder thermostat and any mid-position valves are correctly set and wired. A stuck or incorrectly set DHW thermostat can cause repeated or prolonged anti-cycle behaviour.

4. Check pump operation: listen for the boiler pump during CH or DHW demand. Poor circulation (blocked pump, air in system) can cause unusual temperature gradients and repeated inhibition. If you suspect the pump is not running, do not try to remove electrical covers—note it for the engineer.

5. Inspect for blocked condensate or visible plumbing issues only if safe and external (frozen condensate in cold weather can cause faults). Do not attempt internal condensate trap work unless comfortable and isolated.

6. Log occurrences: Note times, what was happening (e.g., hot water used, DHW demand), and any other codes. This information helps a visiting engineer diagnose intermittent issues.

When to call a professional:

- Call a Gas Safe registered engineer if 305 0 persists for a long time (more than 30 minutes) with loss of hot water, if it repeats frequently during normal use, or if other fault codes appear alongside it.

- Call a professional if you suspect circulation problems, pump failure, sensor faults, or if resets and basic checks do not return the boiler to normal operation.

- Do not attempt to replace sensors, gas valves, PCB, or any sealed combustion components yourself.

Final note:

305 0 is normally an anti-cycle/information state and often requires no action other than waiting or a simple reset. If you are in any doubt or other symptoms are present, contact a Gas Safe registered engineer and provide them with the display code, frequency of occurrence, and the log of what you observed.