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Viessmann · Viessmann Vitocal 250-A (One Base, monobloc) · Procedure

Viessmann Vitocal 250-A: water pressure too low or too high, and the air vent alarm

Summary (editorial)

The manual explains the pressure messages and the air vent alarm and what the user may do before calling the installer.

✎ editorial – written from the cited sources, not a manufacturer statement. Status: draft.

From the manufacturer's documentation (English source wording, with page)

  1. Messages are displayed on the HMI programming unit[1]
  2. F.74 pressure too low: top up with water, vent the system[2]
  3. Check the pre-charge pressure of the expansion vessel[3]
  4. F.87: safety valve in the indoor unit has opened; reduce the system pressure[4]
  5. Reduce the system pressure[5]
  6. Escaping refrigerant can lead to explosions[6]
  7. F.867 during operation: shut off the hydraulic connection between indoor and outdoor unit[7]
  8. Work on refrigerant circuit with flammable refrigerant requires specific qualifications[8]

⚠ Work on refrigerant circuits, mains electricity and PV DC wiring is for qualified technicians only.

The Polish page has more detail (plain-language explanation, safe checks, guides): Read in Polish →

Sources

Every statement has a footnote to the document and PDF page. “Quote verified” means the quote was found automatically in the text of that page.

  1. [1] Viessmann – Service instructions: System configuration and diagnosis for heat pumps with Viessmann One Base (6194799 GB, 3/2022) (6194799 GB (3/2022)) , p. 7 manufacturer document – copy from a distributor quote verified Messages are displayed on the HMI programming unit
  2. [2] Viessmann – Service instructions: System configuration and diagnosis for heat pumps with Viessmann One Base (6194799 GB, 3/2022) (6194799 GB (3/2022)) , p. 51 manufacturer document – copy from a distributor quote verified Top up with water. Vent the system.
  3. [3] Viessmann – Service instructions: System configuration and diagnosis for heat pumps with Viessmann One Base (6194799 GB, 3/2022) (6194799 GB (3/2022)) , p. 51 manufacturer document – copy from a distributor quote verified Check the pre-charge pressure of the expansion vessel.
  4. [4] Viessmann – Service instructions: System configuration and diagnosis for heat pumps with Viessmann One Base (6194799 GB, 3/2022) (6194799 GB (3/2022)) , p. 52 manufacturer document – copy from a distributor quote verified The safety valve in the indoor unit has opened.
  5. [5] Viessmann – Service instructions: System configuration and diagnosis for heat pumps with Viessmann One Base (6194799 GB, 3/2022) (6194799 GB (3/2022)) , p. 52 manufacturer document – copy from a distributor quote verified Reduce the system pressure.
  6. [6] Viessmann – Service instructions: System configuration and diagnosis for heat pumps with Viessmann One Base (6194799 GB, 3/2022) (6194799 GB (3/2022)) , p. 64 manufacturer document – copy from a distributor quote verified Escaping refrigerant can lead to explosions that result in very serious injuries.
  7. [7] Viessmann – Service instructions: System configuration and diagnosis for heat pumps with Viessmann One Base (6194799 GB, 3/2022) (6194799 GB (3/2022)) , p. 64 manufacturer document – copy from a distributor quote verified Shut off the hydraulic connection between the indoor and outdoor unit.
  8. [8] Viessmann – Service instructions: System configuration and diagnosis for heat pumps with Viessmann One Base (6194799 GB, 3/2022) (6194799 GB (3/2022)) , p. 50 manufacturer document – copy from a distributor quote verified circuit with flammable refrigerant are required