Heat pumps · Error codes · Immergas
PbImmergas · MAGIS M monobloc R32 (M4-M30 T) - sold in UK as Alpha Magis M
Pb on an Immergas MAGIS M monobloc R32 - sold in UK as Alpha Magis M: Antifreeze protection
Short answer
On an Immergas heat pump, Pb means: Antifreeze protection. The heat pump keeps running with some functions stopped.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Antifreeze protection.
Likely causes:
- Unit automatically returns to normal operation.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Information only |
| Engineer needed? | No |
The heat pump keeps running with some functions stopped.
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
- No action needed - the manual says the unit automatically returns to normal operation.
- 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
- Unit automatically returns to normal operation.
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 128 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026