Heat pumps · Error codes · Daikin
EC-04Daikin · Altherma
EC-04 on a Daikin Altherma: Tank preheating
Short answer
On a Daikin heat pump, EC-04 means: Tank preheating. The heat pump keeps running.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Tank preheating.
Part involved: tank preheating.
When it shows: Unit is preheating the tank.
Is it safe?
| Does the heat pump stop? | No |
|---|---|
| Severity | Information only |
The heat pump keeps running.
Resetting itself: yes.
Manual reset: Automatic reset.
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 the domestic hot water / programme schedule and settings on the user interface (Daikin notes AH-00 can be caused by large hot-water draws or stopping the tank during disinfection).
- Daikin documents this code as resetting automatically once the condition clears; if it keeps coming back, contact 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
- | Troubleshooting.
Who to ask for: Heat pump installer / heating engineer.
Certification: G3 unvented hot water competence for cylinder safety components.
What you might notice
What owners and engineers report
5 owner and engineer reports mention this.
- Hot water not hot enough on the Altherma: 5 reports
Sources
- Service manual Daikin Altherma 3 M EBLA/EDLA04~08E (ESIE22-09) ↗ · ESIE22-09 · page 50 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026