F.1076 on a Viessmann One Base: Compressor start count exceeded with oil temperature too low
Short answer
On a Viessmann heat pump, F.1076 means: Compressor start count exceeded with oil temperature too low. 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: Compressor start count exceeded with oil temperature too low.
Part involved: Compressor start count exceeded with oil temperature too low.
When it shows: System characteristics: Refrigerant circuit locked.
Likely causes:
- Compressor thermal overload:.
- Refrigerant circuit pressure too low.
- Viscosity of compressor oil too low Further message: I.110, 10 times.
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Severity | Safety lockout |
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Resetting itself: Not stated per code in Viessmann document 6199893 GB 01/2026 (VSA00009).
Manual reset: Measures include resetting/unlocking the refrigerant circuit via HMI service menu "Reset outdoor unit" or ViGuide (engineer, password-protected; 6199893 p.118).
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.
What the engineer will check
- Check the operating pressure on the secondary side: Max. 3 bar (0.3 MPa).
- Check refrigerant lines for mechanical damage. Refrigerant lines must be connected free of load and torque stress.
- Check condenser for mechanical damage. If necessary, purge the condenser.
- Check refrigerant oil for correct viscosity and charge weight. Purge the refrigerant circuit.
- Check oil sump heater on VCMU refrigerant circuit controller: See F.1009.
- Check oil sump temperature sensor:.
- Check connection X20.3/X20.4 on the VCMU refrigerant circuit controller:.
- Check wires and plugs for correct seating.
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 for contractors: Heat pumps in monoblock design incl. hybrid – System configuration and diagnostics (Vitocal 150-A/151-A/250-A/252-A, IDU-A, AWMOF-151/251, AquaSnap 30AWH, BI-BLOC R290) (6199893 GB 01/2026) ↗ · 6199893 GB 01/2026 (VSA00009) · page 182-183 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026