369 on an Atlantic heat pump: External fault (safety component)
Short answer
On an Atlantic heat pump, 369 means: External fault (safety component). 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: External fault (safety component).
Likely causes:
- External safety component (e.g. underfloor safety thermostat) connected to input EX3 has tripped.
On the Alféa Excellia A.I. / Excellia Duo A.I. (R410A split, 11-16)
The manual says: External.
Likely causes:
- External safety component (e.g. underfloor safety thermostat) connected to input EX3 has tripped.
On the Alféa Extensa A.I. / Extensa Duo A.I. R32 (split, 3-10)
The manual says: External.
Likely causes:
- External safety component (e.g. underfloor safety thermostat) connected to input EX3 has tripped.
On the Alféa Extensa + / Extensa Duo + (R410A split, 5-16)
The manual says: External fault (safety component).
Likely causes:
- External safety component (e.g. underfloor safety thermostat) connected to input EX3 has tripped.
On the Alféa Hybrid Duo (heat pump + integrated fuel-oil boiler)
The manual says: Hydraulic pressure fault.
Likely causes:
- Low heating water pressure.
Is it safe?
On the Alféa Excellia / Excellia Duo (R410A split, 11-16, pre-A.I.)
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Safety lockout |
| 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 |
|---|---|
| Severity | Safety lockout |
| 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 |
|---|---|
| Severity | Safety lockout |
| 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 |
|---|---|
| Severity | Safety lockout |
| 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 |
|---|---|
| Severity | Safety lockout |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
What you can check
On the Alféa Excellia / Excellia Duo (R410A split, 11-16, pre-A.I.)
- Note the error number/LED pattern shown and give it to your installer.
On the Alféa Excellia A.I. / Excellia Duo A.I. (R410A split, 11-16)
- Note the error number/LED pattern shown and give it to your installer.
On the Alféa Extensa A.I. / Extensa Duo A.I. R32 (split, 3-10)
- Note the error number/LED pattern shown and give it to your installer.
On the Alféa Extensa + / Extensa Duo + (R410A split, 5-16)
- Note the error number/LED pattern shown and give it to your installer.
On the Alféa Hybrid Duo (heat pump + integrated fuel-oil boiler)
- Check the heating system pressure gauge reading (typically 1-2 bar per Atlantic maintenance guidance).
- Check the filling loop is closed after any top-up.
- Note the error number/LED pattern shown and give it to your installer.
What the engineer will check
On the Alféa Excellia / Excellia Duo (R410A split, 11-16, pre-A.I.)
- Identify and check the safety device wired to the external-fault input (EX3); find why it tripped before resetting.
Who to ask for: heating / electrical.
On the Alféa Excellia A.I. / Excellia Duo A.I. (R410A split, 11-16)
- Identify and check the safety device wired to the external-fault input (EX3); find why it tripped before resetting.
Who to ask for: heating / electrical.
On the Alféa Extensa A.I. / Extensa Duo A.I. R32 (split, 3-10)
- Identify and check the safety device wired to the external-fault input (EX3); find why it tripped before resetting.
Who to ask for: heating / electrical.
On the Alféa Extensa + / Extensa Duo + (R410A split, 5-16)
- Identify and check the safety device wired to the external-fault input (EX3); find why it tripped before resetting.
Who to ask for: heating / electrical.
On the Alféa Hybrid Duo (heat pump + integrated fuel-oil boiler)
- Find and repair the water leak, check expansion vessel and pressure switch.
Who to ask for: heating.
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