Error E110

Safety first

1) If you smell gas, leave the property immediately and call the gas emergency number. Do not attempt any DIY. 2) Turn the boiler off and switch off the electrical supply at the isolator. Allow the boiler and pipework to cool before touching. 3) Do not repeatedly press the reset button if the fault returns immediately — persistent lockouts need a qualified engineer.

Initial homeowner checks you can safely do

1) Check the pressure gauge on the boiler. Ideal cold pressure is typically about 1.0–1.5 bar. If pressure is significantly below 1.0 bar, low pressure can contribute to overheating. 2) Visually inspect for any obvious leaks under or around the boiler and radiators. 3) Check external condensate pipe (if fitted) for signs of freezing or blockage; in winter a frozen condensate pipe can cause faults. 4) Ensure flue and air intake vents are not obstructed by debris, snow, or bird nests. 5) Listen at the boiler for the pump when the system calls for heat (after a restart): you may hear a faint hum; if completely silent when it should be running, there may be a circulation fault.

Step-by-step troubleshooting and simple fixes

1) Repressurise the system if pressure is low: follow your boiler manual for using the filling loop. Raise pressure slowly to about 1.2–1.5 bar, then close the loop and check for leaks. Only do this if you are comfortable with the filling loop procedure. 2) Bleed radiators to remove airlocks: starting with the lowest radiator in the house, use a bleed key to release trapped air until water flows, then top up pressure if it falls. 3) Reset the boiler once pressure and bleeding are addressed: press and hold the reset button as per the manual (commonly 3–5 seconds). Wait to see if the E110 clears and the boiler runs normally. 4) Check condensate pipe: if blocked or frozen, thaw carefully with warm (not boiling) water or a warm cloth on the outdoor section, or clear visible debris; do not dismantle internal boiler components. 5) Observe radiators and pipe temperatures when the boiler runs: large temperature differences between flow and return or cold radiators with the pump running suggest circulation problems or a seized pump.

When to call a professional (and what to tell them)

1) Call a Gas Safe registered engineer if the E110 remains after the basic steps, if you suspect a seized/jammed pump, if the boiler repeatedly locks out, if there are electrical/PCB or sensor faults, or if you find internal leaks. 2) Give the engineer the exact error code (E110), describe what you have already tried (pressure check, bleeding, reset), note any unusual noises, and whether pressure drops again or radiators remain cold. 3) Do not attempt to remove or service the pump, replace sensors, or work on gas or PCB components yourself — these require a qualified engineer.

Other notes and cautions

1) Repeatedly resetting a locked-out boiler without fixing the cause can cause further damage. 2) If system pressure keeps dropping after you repressurise, there may be a leak or another fault needing professional investigation. 3) If an engineer finds sensor, pump or PCB faults, they will advise repair or replacement. Always use a Gas Safe registered engineer for any work on the gas side or internal boiler components.