F.914 on a Viessmann One Base: Inverter temperature too high
Short answer
On a Viessmann heat pump, F.914 means: Inverter temperature too high. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Inverter temperature too high.
Part involved: Inverter temperature too high.
When it shows: System characteristics: Heat pump does not start.
Likely causes:
- Inverter temperature too high.
- Further messages: I.75 and I.121.
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
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).
What the engineer will check
- Isolate the system from the power supply.
- Check inverter heat sink for dirt. Ensure heat transfer.
- Check evaporator for unobstructed flow. If necessary, clean evaporator.
- Check fan and fan motor bearings for damage and blockages: Turn slowly by hand. Remove any blockages. Replace fan motor if necessary.
- 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).
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 139 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026