F.74 Water pressure too low, burner locked out

What the control is telling you

Burner locked out and internal pump off; no heating or DHW.

Applies to: Vitodens 200-W B2HE 85, 120, 150, 199

Likely causes

• Low system pressure
• Leak
• Expansion tank pre-charge
• Pressure sensor fault

Test and repair steps

1. Top up with water and vent the system.
2. If repeated check system pressure sensor with an external gauge.
3. Check expansion tank pre-charge.
4. Check target system pressure and range settings.

Models that show this code

4 models in Vitodens 200-W B2HE

Other codes on the same units

• F.70 BCU internal error
• F.71 Fan speed too low
• F.72 Fan idle state not reached
• F.73 BCU internal communication error
• F.762 System pressure too low
• F.763 Gas pressure too high
• F.764 Lag boiler reports a fault
• F.765 Lead boiler communication error