BoilerFaultCodesViessmann 446 Fault Code
The Viessmann 446 fault code means: your boiler has detected a conflicting reading between its internal temperature sensors and has shut down as a safety precaution to prevent overheating.. It appears on 1 Viessmann model in our database.
Technical description: Deviation, flow temperature sensor/high limit safety cut-out
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Avoid the next call-out bill
A cover plan would handle faults like 446: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.
Viessmann models that show the 446 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann 446 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026