Boiler displays error code 25, boiler overheats and shuts down

Warning: Overheating can damage the boiler and system. Parts of the system may be very hot. Allow the boiler to cool before touching any pipework.

• Check system pressure: Ensure pressure is 1.0–1.5 bar. Low pressure can cause poor circulation and overheating. Top up if needed.
• Check radiator valves: Make sure at least some radiators are open. If all TRVs are closed, the boiler cannot dissipate heat.
• Listen for pump operation: When the boiler tries to run, you should hear the pump. If it is silent or very noisy, the pump may be seized or airlocked.
• Bleed pump (engineer task on most models): Many Intergas pumps are internal; bleeding should be done by an engineer.
• Engineer actions: The engineer will check pump operation, clean or replace the plate heat exchanger, verify filters and strainers are clear, and test the overheat thermostat and NTC sensors.