370 on an Atlantic heat pump: Outdoor unit connection error - see interface-board LED codes (also shown during start phase)
Short answer
On an Atlantic heat pump, 370 means: Outdoor unit connection error - see interface-board LED codes (also shown during start phase). The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 5 sources
What it means
On the Alféa Excellia / Excellia Duo (R410A split, 11-16, pre-A.I.)
The manual says: Outdoor unit connection error - see interface-board LED codes (also shown during start phase).
Likely causes:
- Fault in the outdoor unit (details via the interface-board/outdoor LED codes).
On the Alféa Excellia A.I. / Excellia Duo A.I. (R410A split, 11-16)
The manual says: Thermodynamic source.
Likely causes:
- Fault originating in the outdoor unit; UI shows 370 followed by the outdoor unit error.
- Fault in the outdoor unit (details via the interface-board/outdoor LED codes).
On the Alféa Extensa A.I. / Extensa Duo A.I. R32 (split, 3-10)
The manual says: Thermodynamic source.
Likely causes:
- Fault originating in the outdoor unit; UI shows 370 followed by the outdoor unit error.
- Fault in the outdoor unit (details via the interface-board/outdoor LED codes).
On the Alféa Extensa + / Extensa Duo + (R410A split, 5-16)
The manual says: Outdoor unit connection error - see interface-board LED codes (also shown during start phase).
Likely causes:
- Fault in the outdoor unit (details via the interface-board/outdoor LED codes).
On the Alféa Hybrid Duo (heat pump + integrated fuel-oil boiler)
The manual says: Outdoor unit connection error - see interface-board LED codes (also shown during start phase).
Likely causes:
- Fault in the outdoor unit (details via the interface-board/outdoor LED codes).
Is it safe?
On the Alféa Excellia / Excellia Duo (R410A split, 11-16, pre-A.I.)
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: 1.
On the Alféa Excellia A.I. / Excellia Duo A.I. (R410A split, 11-16)
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
On the Alféa Extensa A.I. / Extensa Duo A.I. R32 (split, 3-10)
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
On the Alféa Extensa + / Extensa Duo + (R410A split, 5-16)
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: 1.
On the Alféa Hybrid Duo (heat pump + integrated fuel-oil boiler)
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
What you can check
- Check the heat pump isolator and consumer-unit breakers are on (do not open any casing).
- Check the outdoor unit is not blocked by leaves, debris or snow.
- Note the error number/LED pattern shown and give it to your installer.
What the engineer will check
- Read the interface-board LED code / outdoor unit error and diagnose accordingly.
Who to ask for: refrigeration / heat pump.
What you might notice
Sources
- alféa excellia duo Maintenance Document (U0546279_1738_EN_16) ↗ · U0546279_1738_EN_16 · page 68 · Reviewed 23 September 2026
- Alféa Excellia A.I. Installation manual (U0611757_1876_EN_14) ↗ · U0611757_1876_EN_14 · page 76 · Reviewed 23 September 2026
- Alfea Extensa A.I. R32 Installation manual (U0671217_2114_EN_11) ↗ · U0671217_2114_EN_11 · page 70 · Reviewed 23 September 2026
- alféa extensa + Installation and operating manual (doc 1734-10, 1734-EN) ↗ · 1734-10 · page 74 · Reviewed 23 September 2026
- alféa hybrid duo Installation and commissioning instructions (doc 1440-13) ↗ · 1440-13 · page 65 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026