Furnace display shows low water pressure / water shortage alarm, burner blocked

Safety: Allow the system to cool before adding water. Use only approved fill water quality as per Hoval documentation.

• Check pressure gauge: Read the system pressure on the Hoval display or mechanical gauge. Typical cold pressure is around 1.0–1.5 bar (check your manual).
• Top up system: Locate the filling loop or make-up valve. Slowly open the valve and watch the gauge rise to the recommended pressure. Close the valve securely afterwards.
• Inspect for leaks: Walk the system and look for visible leaks at radiators, valves, and under the furnace. Repair any leaks before repeated topping up.
• Check expansion vessel: If pressure rises too high when hot and drops to zero when cold, the expansion vessel may be flat. A technician should check and recharge or replace it.
• Reset alarm: Once pressure is correct and stable, reset the alarm on the Hoval controller.