56 on a Viessmann Vitotronic 200: Condenser frost risk
Short answer
On a Viessmann heat pump, 56 means: Condenser frost risk. 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:
- Condenser frost risk.
- Frost protection, secondary circuit.
Part involved: Condenser frost risk; Frost protection, secondary circuit.
When it shows: Type "Note" (H) - triggers "07 Refrigerant circuit" on the heat pump control unit. Heat pump characteristics: Compressor OFF; Refrigerant circuit reversal OFF 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: Both compressors OFF; Refrigerant circuit reversal OFF Type "Note" (H) - triggers "07 Refrigerant circuit" on the heat pump control unit. Heat pump characteristics: Only in cooling mode: Compressor OFF.
Likely causes:
- Condenser frost risk.
- Frost protection, secondary circuit.
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
- Check hydraulics in the secondary.
- circuit, e.g. whether all shut-off valves are fully open. Check secondary circuit flow rate.
- Check flow and return temperature.
- sensor in the secondary circuit: See "Controller and sensor PCB". Check amount of refrigerant. Adjust.
- the amount of refrigerant if necessary. Check temperature sensors in the.
- refrigerant circuit: See "EEV PCB [4-3] / [4-4] ".
- refrigerant circuit: See "EEV PCB [4-6] / [4-7] ".
- in the secondary circuit. Check flow and return temperature.
- sensor in the secondary circuit. Check amount of refrigerant. Adjust.
- if necessary. Check temperature sensors in the.
- refrigerant circuit.
- in the secondary circuit. Check secondary circuit flow temperature sensor in the appliance. Check refrigerant charge. Adjust if.
- necessary. Check temperature sensors in the.
- No action required.
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 169, 175, 163, 181, 184 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026