F.74 — Burner locked out (Water pressure too low)

What does F.74 mean?

The burner is locked out, and there is no central heating or domestic hot water heating because the water pressure in the system is too low. This is a common issue that can often be resolved by topping up the system.

• System water pressure too low
• Faulty system pressure sensor
• Incorrect diaphragm expansion tank pre-charge pressure
• Incorrect target system pressure or range settings

Click steps to track your progress.

1. 1

   Top up the system with water to the recommended pressure, usually indicated on a pressure gauge.

2. 2

   Vent the heating system to remove any trapped air, as airlocks can affect pressure.

3. 3

   If the fault occurs repeatedly, contact a qualified technician to check the system pressure sensor or diaphragm expansion tank.