F.74 — Burner locked out: Low water pressure, no heating or hot water

What does F.74 mean?

The burner is locked out, and there is no central heating or domestic hot water (DHW) heating because the water pressure is too low. The internal circulation pump is also off.

• Water pressure too low
• Faulty system pressure sensor
• Incorrect diaphragm expansion tank pre-charge pressure
• Incorrect settings for target system pressure and range

Click steps to track your progress.

1. 1

   Check the boiler's pressure gauge and top up the system with water until the pressure is within the recommended range (usually 1-1.5 bar).

2. 2

   Vent the heating system and radiators to remove any trapped air.

3. 3

   If the fault occurs repeatedly, contact a qualified heating engineer to check the system pressure sensor and the diaphragm expansion tank.