Boiler displays 110, very hot casing, no heating or hot water

Safety: Turn off power and gas. Allow the boiler to cool completely before attempting any reset.

• Check system pressure and bleed: Ensure adequate pressure and bleed radiators and the pump to remove air.
• Inspect pump: Confirm the circulation pump runs when there is demand. A non-running pump will cause rapid overheating.
• Reset overheat thermostat: Some Ariston models have a manual reset overheat stat inside the boiler. With power off, remove the front cover and press the small reset button on the overheat thermostat if present. Only do this once; repeated trips indicate a serious fault.
• Check for limescale/sludge: Kettling noises or very hot flow pipe with cool return suggest blockage. Professional cleaning or replacement of the primary heat exchanger may be required.
• Sensor check: A faulty overheat NTC sensor can falsely trigger 110. An engineer can test and replace it.