HVACopediaViessmann · Boiler
F.527 Wrong HMU parameter set
What the control is telling you
Burner in a fault state.
Applies to: Vitodens 200-W B2HE 85, 120, 150, 199
Likely causes
- Incorrect parameter set
Test and repair steps
- Flash the HMU with the correct parameter set.
Models that show this code
4 models in Vitodens 200-W B2HE
Other codes on the same units
- F.49 Flue gas temperature sensor open circuit
- F.5 Sensor circuit fault at plug 33 (X6)
- F.50 Flue gas temperature sensor short circuit
- F.517 Remote control not working
- F.528 Wrong BCU parameter set
- F.530 Solar sensor missing or open
- F.538 System return sensor open (SDIO)
- F.540 Condensate back-up in heat cell
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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.