Furnace shows E10; no heating, and the system pressure gauge may read low.

Safety: Allow the system to cool before adding water. Overfilling can cause relief valve discharge.

• Check pressure gauge: Verify the system pressure is within the range specified by Kospel (commonly around 1.0–1.5 bar when cold). If low, proceed to fill.
• Top up system: Open the filling loop valves slowly and watch the gauge rise. Close the valves once the correct pressure is reached. Never leave the filling loop permanently connected if local codes prohibit it.
• Bleed air: Bleed radiators and high points to remove trapped air, then recheck and adjust pressure.
• Inspect for leaks: Look for visible water around radiators, valves, and under the furnace. Fix leaks before repeatedly topping up.
• Check pressure sensor: If pressure is correct but E10 persists, the water pressure sensor or switch may be faulty and require replacement.