Boiler displays E05, shuts down on high temperature, may be hot to touch on flow pipe

Safety first: Turn off the boiler and allow it to cool fully before touching any pipework.

User checks:

• Bleed air from radiators starting from the highest point; top up system pressure to 1.0–1.5 bar afterwards.
• Ensure all radiator valves are open and that at least some radiators are calling for heat.
• Reset the boiler once after the system has cooled.

Engineer checks:

• Verify pump operation: listen for running noise and feel for vibration; check that the pump is not seized.
• Check for blocked filters or sludge in the system; clean the system filter and consider a system flush.
• Test the overheat thermostat for correct operation and continuity when cool; replace if faulty.
• Inspect the primary heat exchanger for scale or blockage; descale or replace if severely restricted.

Repeated E05 trips indicate a circulation or heat exchanger problem that should be addressed by a heating engineer.