Heat pumps · Error codes · Carrier
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6 on a Carrier heat pump: Loss communication to NUI control
Short answer
On a Carrier heat pump, 6 means: Loss communication to NUI control. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 2 sources
What it means
On the AquaSnap / AquaSnap Plus 30AWH (R410A inverter monobloc, 2010-2018 generations)
The manual says: Loss communication to NUI control.
Likely causes:
- Configuration/communication fault.
On the AquaSnap Plus 30AWH (R410A monobloc)
The manual says: Loss communication to NUI control.
Likely causes:
- Check cables between GMC board and NUI.
- check GMC boards and NUI.
Is it safe?
On the AquaSnap / AquaSnap Plus 30AWH (R410A inverter monobloc, 2010-2018 generations)
| Does the heat pump stop? | Yes |
|---|---|
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
On the AquaSnap Plus 30AWH (R410A monobloc)
| Does the heat pump stop? | No |
|---|---|
| Severity | Warning |
| Engineer needed? | Yes |
The heat pump keeps running.
What you can check
On the AquaSnap / AquaSnap Plus 30AWH (R410A inverter monobloc, 2010-2018 generations)
- Note the code/LED pattern and the model from the rating plate, then contact a heat pump/refrigeration engineer.
- Check the heat pump's breaker/isolator at the consumer unit is on.
On the AquaSnap Plus 30AWH (R410A monobloc)
- Read and note the exact code shown on the controller display.
- Check the heat pump's breaker/isolator at the consumer unit is on.
- Restart once via the controller (OFF then ON) as the manual allows; if the code returns, call an engineer.
What the engineer will check
On the AquaSnap / AquaSnap Plus 30AWH (R410A inverter monobloc, 2010-2018 generations)
- Check NUI/GMC wiring, parameters and board.
Who to ask for: refrigeration / heat pump engineer.
Certification: Electrical competence for work inside the unit.
On the AquaSnap Plus 30AWH (R410A monobloc)
- Check cables between GMC board and NUI.
- check GMC boards and NUI.
What you might notice
Sources
- Carrier 30AW AquaSnap Plus Reversible Inverter - Installation, Operation and Maintenance Instructions (air/water cycle heat pump), Order No. L010130H42 01.2017 (supersedes 12.2015) ↗ · L010130H42 01.2017 · page 26 · Reviewed 23 September 2026
- Carrier 30AWH AquaSnap Plus Service Manual, Engineering Department of Italy, November 2010 (SM_30AW) ↗ · November 2010 · page 74 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026