93 on a Viessmann Vitotronic 200: Compressor drive fault
Short answer
On a Viessmann heat pump, 93 means: Compressor drive fault. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 2 sources
What it means
The manuals for this range word it in different ways:
- Compressor drive fault.
- Retn temp.sensor solar: No solar DHW heating or; No heating of the ice store.
Part involved: Compressor drive fault; Retn temp.sensor solar.
When it shows: Type "Fault" (S) - triggers "05 Refrigerant circuit" on the heat pump control unit. Heat pump characteristics: Compressor OFF No solar DHW heating or; No heating of the ice store.
Likely causes:
- Compressor drive fault.
- With integral solar control function: Short circuit, return temperature sensor, solar circuit With Vitosolic 200: Short circuit, ice store temperature sensor.
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 in 6150133.
Manual reset: Refrigerant circuit messages cannot be acknowledged in the message history (6150133 p.155); acknowledge the resulting 05/07/A9 message on the control unit.
What you can check
- This code is only visible to engineers in the service menu (Diagnosis > Refrigerant circuit > Message history); homeowners see message 05, 07 or A9 - note that code and call your contractor.
- Note the 2-character message code and message text shown on the Vitotronic 200 display (press OK for details) and give them to your heating contractor (operating instructions 5817913 p.56).
- You may acknowledge the message once with OK as described in the Vitotronic 200 operating instructions; if it reappears, do not keep acknowledging it - call 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
- Test coil resistance at compressor. Resistance on all windings must be similar (±10 %). For mΩ use a suitable measuring device.
- Replace compressor and/or inverter if necessary.
- Check resistance value (NTC 10 k Ω) at plug F23: See "Controller and sensor PCB". Replace sensor if required. Check ice store temperature sensor. Replace ….
Who to ask for: Viessmann-trained heat pump engineer with F-gas refrigeration certification; Viessmann-trained heat pump installer/service engineer.
Certification: F-gas certificate (UK F-gas Regulations; Viessmann: refrigerant work by authorised refrigeration engineers only).
What you might notice
Sources
- Service instructions Vitotronic 200 type WO1C heat pump control unit (air/water split & monobloc, brine/water) (6150133, 2023-07) ↗ · 6150133 VSA00004 · page 160 · Reviewed 23 September 2026
- Service instructions Vitotronic 200 WO1C (5790974 GB, 2023-09) – brine/water & split variants ↗ · 5790974 VSA00002 · page 78 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026