F.867 on a Viessmann One Base: Float air vent valve in the outdoor unit has responded. Too much air in the secondary circuit during venting Quick-action air vent; valve may be faulty Or Refrigerant present in …
Short answer
On a Viessmann heat pump, F.867 means: Float air vent valve in the outdoor unit has responded. Too much air in the secondary circuit during venting Quick-action air vent; valve may be faulty Or Refrigerant present in …. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Float air vent valve in the outdoor unit has responded. Too much air in the secondary circuit during venting Quick-action air vent; valve may be faulty Or Refrigerant present in ….
Part involved: Float air vent valve in the outdoor unit has responded. Too much ….
When it shows: System characteristics: Heat pump off.
Likely causes:
- Float air vent valve in the outdoor unit has responded. Too much air in the secondary circuit during venting Quick-action air vent.
- valve may be faulty Or Refrigerant present in.
- the float air vent valve.
Is it safe?
Switch the heat pump off at its isolator and call an engineer.
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Not stated per code in Viessmann document 6171807 GB 10/2021.
Manual reset: User may acknowledge via HMI after noting the code (6249162 p.57); the message returns if the cause persists.
What you can check
- On the HMI, tap the message and "?" to read the system characteristics and Viessmann's user tips; note the code (e.g. F.xxx) and text for your contractor (operating instructions 6249162 p.57).
- Acknowledge the message once via the HMI; do not acknowledge fault messages several times in quick succession (6249162 p.58) - notify your contractor.
- Check the heat pump breaker/isolator in the consumer unit is ON (do not repeatedly reset a breaker or RCD that keeps tripping).
- If you smell gas/propane near the outdoor unit or suspect a refrigerant leak: switch the heat pump off at its isolator/consumer-unit breaker, keep ignition sources away from the outdoor unit and call a qualified engineer.
What the engineer will check
- Specialist personnel working on a refrigerant circuit with flammable refrigerant are required to have specific qualifications and certification: See "Safety information". Danger Escaping refrigerant can ….
- valve. Replace quick-action air vent valve if required. Restart filling programme.
- If a message appears during operation: Isolate the system from the power supply. Shut off the hydraulic connection.
- between the indoor and outdoor unit. Notify Viessmann Werke Technical Service.
Who to ask for: Viessmann-trained heat pump engineer with F-gas certification and R290 (A3 flammable refrigerant) competence.
Certification: F-gas certificate (UK F-gas Regulations; EU 2015/2067 Cat. I cited by Viessmann) plus A3/R290 competence per EN 378-4 or IEC 60335-2-40 Annex HH (6202263 p.2).
What you might notice
Sources
- Installation and service instructions Vitocal 150-A, AWO(-M)-E-AC/AWO(-M)-E-AC-AF 151.A (6171807, 2021-10) ↗ · 6171807 VSA00001 · page 113 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026