Error D.61

Safety precautions:

1) If you smell gas, evacuate the building immediately, do not operate electrical switches or the boiler, ventilate if safe to do so, and call the gas emergency number or your gas supplier immediately. Do not try to relight or reset the boiler.

2) If you see water leaks, excessive smoke, or signs of overheating, isolate the boiler electrical supply and call a Gas Safe engineer.

3) Only perform external, non-intrusive checks. Do not open the boiler casing or attempt internal repairs—these must be done by a Gas Safe registered engineer.

Initial checks a homeowner can do:

1) Note and record the exact display messages: the D.61 plus any F-codes or other messages shown before or after it. This information is valuable for the engineer.

2) Check boiler pressure on the gauge. Typical operating pressure is around 1–1.5 bar when cold. If pressure is below 1.0 bar, top up using the filling loop following the manufacturer’s instructions, then try a reset.

3) Check the mains gas supply: confirm other gas appliances (hob, gas fire) are working. If no gas to the property, contact your gas supplier.

4) Check the condensate discharge pipe (external frost blocks are common in cold weather) and the flue terminal for visible obstructions (birds' nests, debris). Clear any visible blockage at the external end only if safe to do so.

5) Check for obvious signs of electrical issues: blown household fuses/trips, the boiler’s fused spur switched on, and any water ingress or corrosion on external cable entries or the flue area.

Specific diagnostic and fix steps (homeowner-level):

1) Reset procedure: locate the boiler reset button (refer to your manual). Press and hold for the time recommended by the manual (commonly a few seconds up to 10s). Observe whether the boiler attempts ignition and whether the error clears. Do not repeatedly reset more than twice—if the boiler locks out again, leave it off and call an engineer.

2) If the reset clears and the boiler runs normally, monitor it for repeated lockouts and note any conditions when lockouts happen (calling for hot water, low load, cold start, etc.). If the problem reoccurs, record date/time, external temperature, and any other error codes shown and contact an engineer.

3) If pressure was low and you topped up and the boiler still locks out, do not keep resetting. Low pressure can be a symptom of a leak or failed component that needs professional attention.

4) If you found a blocked condensate pipe and safely cleared it, test the boiler with a reset. Frozen or blocked condensate is a common cause of repeated lockouts in cold weather.

5) Check room thermostat, programmer/timers and any wireless controls to ensure they are calling correctly; an intermittent control signal can cause unexpected behavior.

When to call a professional and what to tell them:

1) Call a Gas Safe registered engineer if the D.61 remains after basic checks and a controlled reset, if the boiler locks out repeatedly, if other F-codes are present, or if you suspect ignition, gas valve, electrode, PCB, pump, or heat-exchanger faults.

2) Provide the engineer with the boiler model, serial number, the D.61 diagnostic reading, any accompanying F-codes, a description of what you observed, times of lockouts, recent maintenance history and any steps you have already taken (pressure top-up, condensate cleared, reset attempts).

3) The engineer will perform safe, specialist diagnostics: check ignition sequence, flame signal and electrodes, gas pressure at the boiler, PCB and wiring harness, NTC sensors/flow and return sensors, pump operation and condensate/trap, flue and air supply, and then recommend repairs or parts replacement as required.

Final notes: D.61 is a diagnostic indicator that the boiler has undergone multiple safety lockouts — it should not be ignored. Basic safety and visual checks and a single controlled reset are acceptable for homeowners, but repeated lockouts or any signs of gas, water leaks, overheating, or persistent fault codes require immediate attention from a Gas Safe registered engineer. Do not attempt internal electrical or gas repairs yourself.