Fault 74 means the burner is locked out because system pressure is too low. The manual's first action is: “Top up with water. Vent the system. If the fault occurs repeatedly: Check system pressure sensor with external pressure gauge. Check diaphragm expansion vessel pre-charge pressure. Check settings for set system pressure and range.”
- Model
- Viessmann Vitodens 111-W
- Display shows
- Burner locked out. (74)
- Type
- Fault code
- Source
- Manual p. 71
What 74 means
Burner locked out. p. 71
Common causes
- System pressure too low p. 71
What to do
- Top up with water. Vent the system. If the fault occurs repeatedly: Check system pressure sensor with external pressure gauge. Check diaphragm expansion vessel pre-charge pressure. Check settings for set system pressure and range. p. 71
If 74 is still not resolved
The manual gives no further instruction for this code. Open the code table in the PDF or contact Viessmann service.
This page summarises what the manufacturer’s manual says about 74; each statement links to the page it comes from, and quoted lines are copied word for word. It is not a substitute for the manual or for a qualified installer. ManualLib is not affiliated with Viessmann. Found a mistake? Report an error.