85 on a Viessmann Vitotronic 200: Temperature at inverter too low due to low outside temperature
Short answer
On a Viessmann heat pump, 85 means: Temperature at inverter too low due to low outside temperature. 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:
- Temperature at inverter too low due to low outside temperature.
- Temperature at inverter (IGBT) too low.
Part involved: Temperature at inverter too low due to low outside temperature; Temperature at inverter (IGBT) too low.
When it shows: Type "Note" (H) - triggers "07 Refrigerant circuit" on the heat pump control unit. Heat pump characteristics: Compressor OFF.
Likely causes:
- Temperature at inverter too low due to low outside temperature.
- Temperature at inverter (IGBT) too low.
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.
What the engineer will check
- No action required.
- Replace inverter.
Who to ask for: Viessmann-trained heat pump engineer with F-gas refrigeration certification.
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 159, 164 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026