Viessmann · Boiler

F.50 Flue gas temperature sensor short circuit

High severity Vitodens 200-W B2HE

What the control is telling you

Burner in a fault state; short circuit on flue gas temperature sensor.

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

Likely causes

Shorted flue gas sensor

Test and repair steps

Check the flue gas temperature sensor and its wiring.
Reset the appliance.

Models that show this code

4 models in Vitodens 200-W B2HE

B2HE-120B2HE-150B2HE-199B2HE-85

Other codes on the same units

F.474 Program run monitoring error
F.477 Solar differential temperature monitoring
F.49 Flue gas temperature sensor open circuit
F.5 Sensor circuit fault at plug 33 (X6)
F.517 Remote control not working
F.527 Wrong HMU parameter set
F.528 Wrong BCU parameter set
F.530 Solar sensor missing or open

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Source: Viessmann Vitodens 200-W B2HE 85/120/150/199 Service Instructions 6167 813-24 (09/2026), Fault messages, p.62-73. Summarized in our own words; check the original manual for your model.

Homeowner looking at this code? See what it means for you and when to call a technician.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.