F.345 Temperature limiter tripped, auto restart after cooling

What the control is telling you

Burner locked out; restarts on its own after cool-down.

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

Likely causes

• Poor heat transfer
• Low water
• Expansion tank pre-charge
• Low flow
• 3-way valve fault
• Scaling of DHW tank or plate exchanger

Test and repair steps

1. Ensure adequate heat transfer.
2. Check fill level and expansion tank pre-charge.
3. Check flow (flow sensor and pump).
4. Test the 3-way diverter valve in the actuator test and vent the system.
5. If it occurs during DHW heating, check the tank or plate heat exchanger for dirt and scale.

Models that show this code

4 models in Vitodens 200-W B2HE

Other codes on the same units

• F.29 Low loss header sensor open circuit
• F.299 Time and date incorrect
• F.30 Low loss header sensor short circuit
• F.342 BCU communication error
• F.346 Ionization current calibration error
• F.348 Gas modulation valve fault
• F.349 Air mass flow not detected correctly
• F.350 Ionization current outside permitted range (BCU)