PP on a Ferroli heat pump: Tw_out - Tw_in unusual protection
Short answer
On a Ferroli heat pump, PP means: Tw_out - Tw_in unusual 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: Tw_out - Tw_in unusual protection.
On the OMNIA M 3.2 monobloc R32 (4-16 kW and 18T-30T)
The manual says: Tw_out - Tw_in unusual protection.
Likely causes:
- Sensor resistance/location.
- Loose connector.
- Broken Tw_in/Tw_out sensor.
- Four-way valve blocked/broken.
On the OMNIA S 3.2 split (wall-hung hydronic unit + OMNIA UE 3.2 outdoor)
The manual says: Tw_out/Tw_in difference not in line with operating mode (heat mode: Tw_out < Tw_in for > 15 min).
Part involved: Tw_out/Tw_in / 4-way valve.
Likely causes:
- Probe resistance/position.
- Connector disconnected.
- Faulty probes.
- Four-way valve blocked or broken.
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 system pressure gauge: the manual says water pressure must be above 1 bar.
- 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).
Who to ask for: heat pump engineer (R290).
Certification: Electrical competence.
On the OMNIA M 3.2 monobloc R32 (4-16 kW and 18T-30T)
- Sensor resistance/location.
- Loose connector.
- Broken Tw_in/Tw_out sensor.
- Four-way valve blocked/broken.
Who to ask for: heat pump engineer.
Certification: Electrical competence for board/wiring work.
On the OMNIA S 3.2 split (wall-hung hydronic unit + OMNIA UE 3.2 outdoor)
- Probe resistance/position.
- Connector disconnected.
- Faulty probes.
- Four-way valve blocked or broken.
Who to ask for: heat pump engineer.
Certification: Electrical competence for board/wiring 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 71 · 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