F.1069 on a Viessmann One Base: Condenser overheating
Short answer
On a Viessmann heat pump, F.1069 means: Condenser overheating. 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: Condenser overheating.
Part involved: Condenser overheating.
When it shows: System characteristics: Heat pump off.
Likely causes:
- Condenser overheating: Evaporator temperature sensor OMT > 65 °C.
- Further messages: A.125 and I.148.
Is it safe?
| 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 6199961 GB 01/2026 (VSA00009).
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).
- Check the outdoor unit is not blocked by leaves, debris or snow.
What the engineer will check
- If message occurs more than twice an hour:.
- Carry out pressure test on refrigerant circuit. If necessary, purge refrigerant circuit.
- Check the temperatures via the "Diagnosis" menu.
- Check the sensor and connection P802 on the ODUC refrigerant circuit controller:.
- Check wires and plugs for correct seating.
- Check connections for contact corrosion.
- Check cables for mechanical damage, e.g. crushing, kinking, chafing or breakage. Check that the sensor including spring is securely fitted.
- Replace ODUC refrigerant circuit controller.
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
- Service instructions: Heat pumps in split design incl. hybrid – System configuration and diagnostics (Vitocal 200-S/222-S One Base) (6199961 GB 01/2026) ↗ · 6199961 VSA00009 · page 167 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026