30 on a Viessmann Vitotronic 200: Operating point outside the compressor application limits for longer than max. time
Short answer
On a Viessmann heat pump, 30 means: Operating point outside the compressor application limits for longer than max. time. 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 manuals for this range word it in different ways:
- Operating point outside the compressor application limits for longer than max. time.
- Secondary circuit return temperature falls below 18 °C 4 times, one after the other, prior to defrosting.
- Flow sensor primary: Operation with temperature value of return temperature sensor in primary circuit, plus 3 K.; If the primary circuit flow and return temperature sensors are both faulty at ….
Part involved: Operating point outside the compressor application limits for longer than max. time; Secondary circuit return temperature falls below 18 °C 4 times, one after …; Flow sensor primary.
When it shows: Type "Note" (H) - triggers "07 Refrigerant circuit" on the heat pump control unit. Heat pump characteristics: Compressor OFF Type "Note" (H) - triggers "07 Refrigerant circuit" on the heat pump control unit. Heat pump characteristics: Defrosting procedure does not start. Operation with temperature value of return temperature sensor in primary circuit, plus 3 K.; If the primary circuit flow and return temperature sensors are both faulty at the same time, the message "A9 Heat pump" is displayed and the heat ….
Likely causes:
- Operating point outside the compressor application limits for longer than max. time.
- Secondary circuit return temperature falls below 18 °C 4 times, one after the other, prior to defrosting.
- Short circuit, primary circuit flow temperature sensor (heat pump air intake or brine inlet).
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Warning |
| 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).
- Check the heating system pressure gauge reading and report a low reading to your contractor; make sure the filling loop is closed.
What the engineer will check
- Check the position of the operating point: See "Compressor travel" and/or "Compressor path".
- If fault persists, notify a specialist.
- Reduce heat demand in the secondary circuit, e.g. lower the set room temperatures. Reduce heat transfer in the secondary circuit.
- Check the position of the operating.
- point: See "Compressor travel" and/or "Compressor path". If fault persists, notify a specialist.
- Check resistance value (Pt500A) at terminals X25.1/ X25.2: See "Controller and sensor PCB".
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 · pages 158, 181, 184, 89 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026