Heat pumps · Error codes · Daikin
UHDaikin · Altherma HT (high temperature split)
UH on a Daikin Altherma HT: Malfunction of system, refrigerant system address undefined
Short answer
On a Daikin heat pump, UH means: Malfunction of system, refrigerant system address undefined. 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: Malfunction of system, refrigerant system address undefined.
Part involved: inter-unit communication / PCB combination.
Likely causes:
- Improper connection of transmission wiring between outdoor unit and outdoor unit outside control adapter; Defect of indoor unit PC board (A1P); Defect of outdoor unit PC board (A1P).
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Resetting itself: unknown.
What you can check
- Read the full error code shown on the user interface and note it, with the date/time, for your installer.
What the engineer will check
- Follow the service-manual troubleshooting flow chart for this code: check improper connection of transmission wiring between outdoor unit and outdoor unit outside control adapter; check defect of indoor unit PC board (A1P); check defect of outdoor unit PC board (A1P).
Who to ask for: Heat pump installer (Daikin-trained).
Certification: None specific; MCS-certified installer recommended.
What you might notice
Sources
- Service Manual Daikin ALTHERMA HT ERSQ/ERRQ 011-016 AA V1/Y1 + EKHBRD (ESIE09-08C) ↗ · ESIE09-08C · page 222 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026