Fault F4 - Air in the system causing pump racing

What does F4 mean?

The boiler exhibits an F4 fault, often accompanied by the pump racing and high-temperature spikes, indicating air trapped within the heating system. This can lead to fault 02 (fixed high limit switch).

• Air in the domestic hot water (DHW) or space heating systems
• Pump issues due to trapped air

Click steps to track your progress.

1. 1

   Bleed air from both the domestic hot water and space heating systems.

2. 2

   Use the yellow cap provided with the DHW solenoid valve to bleed air.

3. 3

   Bleed the pump itself using the screw on the pump head.

4. 4

   If the boiler is connected to an OFF-grid power supply, contact Viessmann support.

5. 5

   For installers: Disconnect pump communication plug #145 and change coding address 013:001 to 013:000.