Error E9 276

Safety first

1) If you smell gas, evacuate the property, call the gas emergency number and a Gas Safe engineer—do not stay in the building. 2) Do not remove the boiler casing or attempt any internal electrical or gas repairs unless you are Gas Safe registered. 3) Do not repeatedly reset the boiler more than once or twice; repeated resets can hide a serious fault and may cause further damage.

Initial homeowner checks (safe, non-intrusive)

1) Turn the boiler off using the front panel switch and isolate electrical power at the external switch if there is one; allow the boiler to cool for 20–30 minutes. 2) Check the system pressure gauge—target pressure when cold is about 1.0–1.5 bar. If pressure is very low (below ~0.8 bar) re-pressurise following the manufacturer’s instructions. 3) After cooling, switch the boiler back on and try one reset of the fault code using the boiler’s reset button. Note whether the code returns immediately or after a short run. 4) Listen for the pump running when the boiler calls for heat (you should hear/feel the pump or mild vibration in pipework). Carefully feel (not touch directly) pipes leaving the boiler: if flow pipes are cold while the boiler is firing, circulation may be blocked. 5) Bleed any radiators to remove air locks which can reduce circulation.

Specific diagnostic actions you can take (still non-intrusive)

1) If the fault was caused by a high flow temperature during a DHW or CH demand, try reducing room thermostat or TRV settings and observe whether the boiler still heats to a very high temperature. 2) Check for obvious external problems: signs of leaks under the boiler, heavy limescale on visible pipework, frozen/blocked external condensate pipe (if present) or blocked flue terminal (look outside for obstructions). 3) Note any other error codes that appear alongside E9 (for example E2 series indicates flow sensor faults). Write down exact code and any cause sub-code shown on the display.

When to call a professional (and why)

1) If the E9 276 returns after one reset, if the boiler does not resume normal operation, or if you cannot restore correct pressure and circulation, call a Gas Safe registered engineer. 2) Do not attempt to test or replace NTC sensors, open the heat exchanger, remove covers, or work on the gas or PCB yourself. Diagnosing a genuine overheat will normally require checking pump operation (including electrical supply to the pump), inspecting the flow sensor and its wiring/connector, checking the safety/high-limit thermostat, and inspecting the heat exchanger for limescale or blockages—these are tasks for a trained engineer. 3) Tell the engineer the exact error code (E9 276), what you have already checked (pressure, reset, whether pump sounds), and whether the boiler has been serviced recently.

Likely professional fixes they may perform (for information only)

A visiting Gas Safe engineer will typically: run diagnostics and log temperatures, check pump function and electrical supply, test or replace the flow NTC sensor, check wiring and connectors, inspect the safety temperature limiter/high limit thermostat, check for flow restriction (airlock, closed valves, blocked heat exchanger or heavy limescale) and may powerflush the system or fit a magnetic filter if sludge is present. If the heat exchanger or control electronics are damaged they will advise on replacement. They will also perform a full safety check after repair.

Final notes

- Don’t ignore the fault or keep resetting repeatedly; this is a safety lockout and indicates a real or potential overheat. - If you are unsure at any stage, or the boiler shows any signs of gas smell, water leaks, or other multiple fault codes, switch the boiler off and call a Gas Safe engineer. - Regular annual servicing reduces the risk of faults like this by catching scale, pump wear, and sensor problems early.