Heat pumps · Error codes · Daikin
U6-36Daikin · Altherma
U6-36 on a Daikin Altherma: Boiler standby abnormality Check boiler Refer to boiler manual
Short answer
On a Daikin heat pump, U6-36 means: Boiler standby abnormality Check boiler Refer to boiler manual. 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 standby abnormality Check boiler Refer to boiler manual.
Part involved: inter-unit communication / PCB combination.
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.
- 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
13 owner and engineer reports mention this.
- No heating on the Altherma: 7 reports
- Controller / thermostat problem on the Altherma: 6 reports
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