Boiler displays F.22, no heating or hot water, pressure gauge low

Safety: Ensure the boiler is cool before topping up. Do not over-pressurise the system.

• Check pressure gauge: Look at the front pressure gauge or digital display. If below ~0.8 bar, the boiler will lock out.
• Top up via filling loop: Locate the filling loop (usually a braided hose with two valves). Open both valves slowly until the pressure rises to 1.2–1.5 bar, then close both valves fully.
• Bleed radiators: Bleed air from radiators starting from the highest floor. Recheck and adjust pressure afterwards.
• Inspect for leaks: Look for visible leaks on radiators, valves, under the boiler, and at the pressure relief valve discharge pipe outside. Fix leaks before repeatedly topping up.
• Check pressure sensor: If pressure is correct but F.22 persists, the water pressure sensor on the hydraulic block may be blocked or faulty. A technician can remove and clean or replace it.