Boiler shows E08 and will not start; may be accompanied by a low or zero pressure reading on the gauge.

Safety: Allow the system to cool before topping up the pressure. Never over-pressurize the system.

• Check pressure gauge: Confirm the gauge reads below the recommended level (usually under 0.8 bar). If so, the boiler correctly detects low pressure.
• Top up the system: Locate the filling loop (flexible hose or built-in valves). Open the valves slowly until the pressure reaches 1.0–1.5 bar, then close both valves tightly.
• Bleed air: Bleed radiators to remove trapped air, then recheck and adjust the pressure.
• Inspect for leaks: Look for visible water around radiators, valves, and under the boiler. Persistent pressure loss indicates a leak that must be repaired.
• Sensor issues: If pressure is normal but E08 persists, the pressure sensor or its tube may be blocked or faulty—this requires a technician.