Error 110

Safety precautions:

- If you smell gas, evacuate the property immediately and call the local gas emergency number. Do not operate electrical switches or the boiler.

- Before working near the boiler switch the electricity supply to the boiler off at the isolator (if safe to do so) and allow the appliance to cool for at least 20–30 minutes.

- If you are not confident performing any checks, or if any work involves the gas supply, electrical wiring, or internal boiler parts, stop and call a Gas Safe registered engineer.

Initial checks a homeowner can do:

1) Allow the boiler to cool then try a reset following the boiler manual. If you don’t have the manual: turn the boiler off at the mains for 30 seconds and switch back on, then attempt the boiler’s reset function. Note whether the E110 returns immediately or after some running time.

2) Check the system pressure gauge when the boiler is cold. Normal cold pressure is typically about 1.0–1.5 bar. If pressure is below ~1.0 bar top up the system using the filling loop (see next steps). If pressure is very high (>2.5 bar) do not top up and call a professional.

3) Inspect for visible water leaks around the boiler, pipework and radiators. A leak can cause pressure loss and circulation issues.

4) Listen and feel: run the heating briefly and check radiators. If the top of a radiator is cold and the bottom hot, or several radiators have cold spots, air may be trapped. If you hear loud banging, gurgling or continuous loud pump noise, circulation may be impaired.

Specific homeowner steps to try (only do the ones you understand):

1) Bleed radiators: place a container/towel under the bleed valve, use a radiator key to open the valve slightly until air hisses out; close when water flows steadily. After bleeding, recheck boiler pressure and top up if needed.

2) Top up system pressure via the filling loop: locate the filling loop (a flexible hose or metal loop with a valve) and open the valve(s) slowly while watching the pressure gauge. Stop when pressure reaches 1.0–1.5 bar and close the valve(s) tightly. Remove or secure the filling loop per your boiler instructions. If you are unsure how to do this, do not force it—call a Gas Safe engineer.

3) Check that any external isolation valves (system/return/flow valves) near the boiler are open. A closed valve can prevent circulation.

4) Observe the pump: with the heating on you may hear/vibrate the pump body; do not touch moving parts. If the pump sounds dead or runs constantly without bringing temperature down, note this for the engineer.

If the error persists after these steps, or if the E110 returns repeatedly:

- Do not attempt to dismantle the boiler or replace internal components yourself. Persistent E110 commonly needs a trained engineer to inspect the safety thermostat (overheat stat), NTC/temperature sensors, the pump and its impeller, the diverter valve motor, the main heat exchanger for blockages/scale or a closed bulkhead valve.

- Call a Gas Safe registered engineer and tell them: the boiler model, the exact error code (E110), the boiler pressure reading, what troubleshooting you have already done (reset, bled radiators, topped up pressure), any noises or leaks observed, and whether the error is intermittent or permanent.

When to call a professional immediately:

- Smell of gas, visible leaks, repeated lockouts, boiler making loud/abnormal noises (kettling, banging), continual loss of pressure, or when you are unsure about any step. A Gas Safe engineer will safely test and, if required, replace the safety thermostat, temperature sensors, pump, diverter valve, or clear blockages/scale in the heat exchanger.

Record-keeping: note times and frequency of the fault and the conditions when it occurs (heating on/off, hot water demand, recent work or changes). This information helps the engineer diagnose the root cause faster.

Summary: try reset, check and restore pressure, and bleed radiators first. If E110 returns, or you find leaks, pump failure signs, or any gas-related concerns, stop and arrange an inspection/repair by a Gas Safe registered engineer.