Error E430

Safety precautions:

- If you smell gas or suspect a gas leak, evacuate the property and call the gas emergency number immediately; do not operate electrical switches or the boiler.

- Before opening any boiler panels or carrying out internal checks, switch the boiler off and isolate electrical supply at the fused spur. If you are not confident, do not open the casing.

- Any work on gas or sealed combustion components must be done by a Gas Safe registered engineer.

Initial homeowner checks you can do (no tools or only a filling key):

1. Note the exact fault code and any additional symbols (for example E430 + flame crossed). Take a photo of the display and note when it occurred (e.g. after bleeding radiators, after a power cut).

2. Check the boiler pressure gauge. Normal cold pressure is typically around 1.0–1.5 bar on domestic systems. If the gauge is below about 0.8–1.0 bar, low pressure can trigger pressure checks and faults.

3. Look for obvious signs of leaks around the boiler, pipework, and radiators. Smell for damp or rust stains and check the condensate pipe in freezing weather.

4. Ensure the filling loop is closed and not leaking. If your filling loop was recently used, confirm all valves were returned to their closed position.

5. Try a simple reset: switch the boiler off at the programmer or fused spur, wait 30 seconds, and switch back on. Some transient sensor or test messages clear after a reset.

Specific diagnostic and fix steps (homeowner level):

1. If the pressure is low, repressurise the system to the recommended operating pressure (usually 1.2–1.5 bar). Follow your boiler manual for the correct filling loop procedure and only open the loop until the pressure rises to the target, then close it and remove/secure the loop according to the manual.

2. After repressurising, reset the boiler and monitor the display. If E430 clears and the boiler runs normally, observe the pressure over the next 24–48 hours. If pressure holds, the issue may have been temporary.

3. If pressure immediately falls again after repressurising, there is likely a leak, a fault with a component (pressure relief valve, expansion vessel, or an internal seal), or a stuck flow/return valve. Check visible pipework and radiators for leaks; bleed any radiators you’ve recently bled and then recheck system pressure.

4. If the pressure is correct but the E430 code persists or you see E430 + flame crossed (indicating the pressure test failed and the boiler has entered a lockout relating to flame/pressure test), do not attempt internal repairs. Note any other codes displayed and the sequence of events (for example if the code appears during firing or during DHW demand).

5. Do not try to adjust or replace sensors, wiring, gas components, or PCB yourself. You can make non-invasive visual checks: ensure sensor and wiring connections are not obviously loose or damaged where they are accessible externally, but do not disconnect or probe inside the appliance unless you are qualified.

When to call a professional:

- Call a Gas Safe registered heating engineer if the fault persists after repressurising and resetting, if pressure keeps dropping, if you find a leak, or if the boiler locks out with E430 + flame crossed or other flame/gas-related codes.

- A Gas Safe engineer will check the pressure sensor, flow switch, filling loop and valves, expansion vessel and PRV, pump operation (airlock or seized pump), and the PCB if required. They will also perform safe gas and combustion checks where necessary.

Additional tips for the visit:

- Keep your notes and photos of the error code, pressure readings, and any events leading up to the fault. This helps the engineer diagnose faster.

- If you attempted to repressurise, tell the engineer whether the pressure held or fell and whether you left any radiators bled.

In summary: start with simple non-invasive checks — check gauge, repressurise to ~1.2–1.5 bar, reset the boiler, and look for leaks. If the code returns, pressure drops, or the code is accompanied by flame/lockout indicators, stop and arrange a Gas Safe engineer to investigate and repair. Do not attempt gas or internal electrical repairs yourself.