Heat pumps · Error codes · Daikin
U8-08Daikin · Altherma H Hybrid
U8-08 on a Daikin Altherma H Hybrid: Boiler communication malfunction
Short answer
On a Daikin heat pump, U8-08 means: Boiler communication malfunction. 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: Boiler communication malfunction.
Part involved: user interface / room thermostat.
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 and sub-code shown on the user interface (Malfunctioning screen; press the help button for Daikin's long description) and note it, with the date/time, for your installer.
- Check any room thermostat/controller display is lit and its batteries (if battery-powered) are not flat; check thermostat and schedule settings.
- Do NOT bleed radiators while an error/malfunction symbol is displayed: Daikin operation manuals warn refrigerant may have leaked into the water circuit - ventilate and call your installer.
What the engineer will check
- See Daikin service manual for this generation (not public).
Who to ask for: Heat pump installer (Daikin-trained).
Certification: None specific; MCS-certified installer recommended.
What you might notice
What owners and engineers report
1 owner and engineer report mentions this.
- No heating on the Altherma H Hybrid: 1 report
Sources
- Installer reference guide Daikin Altherma H Hybrid EJHA04AAV3 + EHY2KOMB-A (4P531180-1E) ↗ · 4P531180-1E · page 220 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026