P4 on a Ferroli heat pump: Compressor discharge temperature too high protection
Short answer
On a Ferroli heat pump, P4 means: Compressor discharge temperature too high protection. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 3 sources
What it means
On the OMNIA LIFE M monobloc R290
The manual says: Compressor discharge temperature too high protection.
On the OMNIA M 3.2 monobloc R32 (4-16 kW and 18T-30T)
The manual says: High discharge temperature protection.
Likely causes:
- Same as P1.
- Tw_out/T1/T5 sensor loose.
On the OMNIA S 3.2 split (wall-hung hydronic unit + OMNIA UE 3.2 outdoor)
The manual says: Compressor discharge temperature (Tp) above maximum allowed.
Part involved: discharge temperature.
Is it safe?
On the OMNIA LIFE M monobloc R290
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Manual reset: Manual 13.3: reset the unit by powering it off and on; if resetting is invalid contact the local dealer.
On the OMNIA M 3.2 monobloc R32 (4-16 kW and 18T-30T)
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Manual reset: Manual (13.4): reset the safety by turning the unit OFF and back ON; if unsuccessful contact your local dealer.
On the OMNIA S 3.2 split (wall-hung hydronic unit + OMNIA UE 3.2 outdoor)
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Manual reset: Manual (sect. 10.3): reset the safety device by turning the unit OFF and back ON; if unsuccessful contact the local dealer.
What you can check
- Check the outdoor unit is not blocked by leaves, debris or snow and has clear airflow.
- Note the code shown on the user interface and contact the installer/Ferroli service.
- The manual says the safety can be reset by switching the unit OFF and back ON; if the code returns, do not keep resetting - call the installer.
What the engineer will check
On the OMNIA LIFE M monobloc R290
- Diagnose per Ferroli/controller service information (Annex G gives description only; the wired controller shows the explanation).
- R290 refrigerant-circuit work: flammable refrigerant, competent/certified engineer only.
Who to ask for: heat pump engineer (R290).
Certification: R290/flammable refrigerant competence for refrigerant work.
On the OMNIA M 3.2 monobloc R32 (4-16 kW and 18T-30T)
- Same as P1.
- Tw_out/T1/T5 sensor loose.
- Refrigerant-circuit diagnosis (F-gas).
Who to ask for: heat pump / refrigeration engineer.
Certification: F-gas certification for refrigerant circuit work.
On the OMNIA S 3.2 split (wall-hung hydronic unit + OMNIA UE 3.2 outdoor)
- Refrigerant-circuit diagnosis (F-gas).
Who to ask for: heat pump / refrigeration engineer.
Certification: F-gas certification for refrigerant circuit work.
What you might notice
Sources
- OMNIA LIFE M - Installation, use and maintenance manual (IT-EN-ES-PT) ↗ · Cod. 3540001560 - Rev. 00 - 07/2024 · page 90 · Reviewed 23 September 2026
- OMNIA M 3.2 mod. 4-16 - Reversible heat pumps for outdoor installation with DC inverter compressor - installation/owner manual (IT-EN...) ↗ · Cod. 3QE47740 - Rev. 02 - 11/2023 · page 74 · Reviewed 23 September 2026
- OMNIA S 3.2 - Installation, use and maintenance manual (IT-EN-ES-PT-FR-DE-NL) ↗ · Cod. 3541V942 - Rev. 01 - 06/2026 · page 126 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026