Boiler displays error 10, often associated with rapid temperature rise and shutdown.

Safety: Turn off power and allow the boiler to cool completely. Surfaces and water may be very hot.

• Check isolation valves: Ensure the flow and return isolation valves under the Biasi boiler are fully open.
• Verify pump operation: With a heat demand, feel the pump for vibration. If it is hot but not turning, it may be seized. Some pumps have a manual freeing screw that an engineer can use.
• Bleed air: Bleed any automatic or manual air vents near the boiler and on high points in the system to remove airlocks.
• Engineer flushing: If radiators are cold or only warm at the top, sludge may be blocking circulation. A technician may need to powerflush or chemically clean the system and possibly the primary heat exchanger.