P5 on an Immergas MAGIS M monobloc R32 - sold in UK as Alpha Magis M: High temperature difference between water inlet and outlet of plate heat exchanger (Tw_out - Tw_in)
Short answer
On an Immergas heat pump, P5 means: High temperature difference between water inlet and outlet of plate heat exchanger (Tw_out - Tw_in). The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: High temperature difference between water inlet and outlet of plate heat exchanger (Tw_out - Tw_in).
Likely causes:
- Shut-off valves.
- Filter.
- Air.
- Water pressure < 1 bar cold.
- Pump speed.
- Expansion vessel.
- Circuit pressure drop.
Is it safe?
| 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 device by switching the unit off and back on; if this fails contact your local dealer.
What you can check
- Check the system pressure gauge (manual: water pressure must be above 1 bar with cold water).
- Note the code on the control panel and contact the installer / Alpha-Immergas authorised service.
- The manual says to reset the safety device by switching the unit off and back on; if the reset fails, contact the dealer - do not keep resetting.
What the engineer will check
- Shut-off valves.
- Filter.
- Air.
- Water pressure < 1 bar cold.
- Pump speed.
- Expansion vessel.
- Circuit pressure drop.
Who to ask for: heat pump engineer.
Certification: Electrical competence.
What you might notice
Sources
- MAGIS M4-30 Block heat pumps - Use and Installation - Instructions and warnings (IE edition), *1.046978ENG* ↗ · 1.046978ENG · page 127 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026