Heat pumps · Error codes · Immergas
H3Immergas · MAGIS M monobloc R32 (M4-M30 T) - sold in UK as Alpha Magis M
H3 on an Immergas MAGIS M monobloc R32 - sold in UK as Alpha Magis M: Fault of refrigerant outlet temperature sensor (T2B) of plate heat exchanger (gas pipe)
Short answer
On an Immergas heat pump, H3 means: Fault of refrigerant outlet temperature sensor (T2B) of plate heat exchanger (gas pipe). 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: Fault of refrigerant outlet temperature sensor (T2B) of plate heat exchanger (gas pipe).
Likely causes:
- Sensor resistance.
- Connector loose/wet.
- Sensor faulty.
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
- 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
- Check sensor resistance; reconnect/dry connector (waterproof adhesive); replace sensor.
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 129 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026