Error E110

Safety precautions:

- If the boiler displays E110, turn off the heating demand at the room thermostat/ programmer and let the boiler cool for 10–15 minutes.

- Do not open the boiler casing or attempt internal repairs unless you are a qualified engineer. Working on gas or live electrical parts is dangerous and must be done by a Gas Safe registered engineer.

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

Initial homeowner checks you can safely do:

1) Reset the boiler: after allowing it to cool, use the boiler reset button or follow the control panel instructions (typically hold reset for 3–5 seconds). Note whether the code clears and whether it returns when you call for heat.

2) Check system pressure: read the pressure gauge on the front of the boiler. Normal cold pressure is typically about 1.0–1.5 bar (factory guidance usually ~1.2 bar). If the pressure is significantly below 1.0 bar, repressurise using the filling loop following the boiler manual. Close the filling loop valves fully after topping up.

3) Inspect for visible leaks: look at pipework, radiators and around the boiler for obvious water leaks which can cause pressure loss and circulation problems. If you find a leak, isolate the boiler and call an engineer.

4) Bleed radiators: trapped air in the system can cause poor circulation and local overheating. While the boiler is off and cooled, bleed radiators starting from the lowest floor and retop up the system pressure if it falls below the recommended value.

5) Check condensate and external pipework: in cold weather a frozen condensate pipe or an external blockage can cause faults—inspect any visible condensate run for ice or blockage and thaw carefully if safe to do so.

6) Listen for the pump: when the boiler calls for heat, carefully listen at the boiler for pump noise or vibration. Do not touch hot or moving parts; if the pump is completely silent but should be running, that suggests a pump failure or electrical issue and you should call an engineer.

Specific diagnostic and next steps (if the basic checks do not clear the fault):

1) If the fault returns after reset and initial checks, switch off the boiler and record the error (take a photo of the code and any other displayed codes, note boiler model and serial). This information helps the engineer.

2) If pressure was low and topping up fixed the fault but pressure drops again over days, there is likely a leak or a problem retaining pressure—call a Gas Safe engineer to investigate.

3) If bleeding radiators and repressurising do not restore circulation, or if you still hear the pump struggling or no pump movement, do not attempt to dismantle the pump—call a Gas Safe engineer. A seized pump, failed motor, or blocked heat exchanger/magnetic filter are common professional repair items.

4) If the safety thermostat or a thermistor has tripped (suspected if the fault points to a sensor or the boiler locks out repeatedly), a qualified engineer must test and replace sensors or the safety thermostat. Do not bypass safety devices.

5) If you suspect sludge or magnetic filter blockage (e.g., radiators cold at the far end), an engineer can inspect and flush the system or clean/replace the filter. That work requires system draining and re-filling.

When to call a professional:

- Call a Gas Safe registered heating engineer if the E110 code returns after your initial checks, if you cannot restore/maintain correct pressure, if you detect pump failure, if there is a persistent circulation problem, if there are leaks, or if any internal component (pump, sensors, safety thermostat, PCB) may be at fault.

- Do not attempt internal repairs, electrical work, gas valve checks or component replacements yourself. These require a qualified engineer and proper safety testing.

What to tell the engineer:

- Give the exact error code (E110) and any additional codes shown, describe the steps you have already taken (reset, pressure check, radiator bleeding), note the boiler model and serial, and provide photos if you took any. This helps the engineer diagnose and carry the right parts.

Final note:

E110 is a protective shutdown for overheating. Many times it is caused by fixable circulation or pressure issues, but persistent or repeating trips indicate a component failure or a more complex system fault that must be resolved by a Gas Safe engineer to ensure safe and reliable operation.