0F Viessmann — Flue Gas Sensor Fault / Exhaust Blockage
At a glance
- Severity
- FAULT STOP
- Domain
- HEATING_SYSTEM
- Reference standard
- EN 15502 / EN 676
What it means
Fault detected by the flue gas sensor or pressure switch.
Probable causes
- Flue pipe obstructed by nests, debris or ice
- Flue gas probe faulty or out of calibration
- Flue pressure switch stuck or defective
- Flue fan not running
- Primary heat exchanger clogged with acidic condensate
Where to start
Measure the flue gas probe resistance and check the pressure switch. Are the values correct?
Full guided diagnosis in the app
The diagnostic tree for this fault has 7 guided steps with measurements, checks and resolutions. You'll find it in HVACIQ, one of the five IndexOS apps: free, works offline.
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