Boiler runs but produces only lukewarm domestic hot water, even at maximum setting.

Safety: Water may still be hot enough to scald; test carefully.

• Check settings: Verify the DHW temperature setpoint on the Defro control panel is at the desired level.
• Reduce flow: Slightly close the hot tap to reduce flow rate; this increases outlet temperature if the boiler is at maximum power.
• Clean filters and plate: Clean the cold inlet filter and consider having the Defro plate heat exchanger descaled or replaced if performance is poor.
• Gas rate check: A technician should verify that the boiler reaches its rated DHW output by checking gas rate and combustion.