L03 on a Toshiba heat pump: Duplicate main hydro unit during group control
Short answer
On a Toshiba heat pump, L03 means: Duplicate main hydro unit during group 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 R32 Estia 1-Series (split, Wall-Mounted and All-in-One)
The manual says: Duplicate main hydro unit during group control.
Part involved: DIP switches, DN/FC codes, addresses, model combination.
When it shows: More than one header unit in the group.
Likely causes:
- Hydro addresses (DN 14).
- Remote controller connection changed after address setting.
On the Estia 5 Series Powerful (Hi Power / Extreme)
The manual says: Duplicate main hydro unit during group control.
Part involved: DIP switches, DN/FC codes, addresses, model combination.
Likely causes:
- Rotary switch SW01 address.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: no.
Manual reset: Cause must be fixed by an engineer; hardware faults reappear until repaired.
What you can check
- Note the check code shown on the remote controller and the outdoor/hydro model numbers before contacting an engineer.
What the engineer will check
On the R32 Estia 1-Series (split, Wall-Mounted and All-in-One)
- Follow manufacturer's check-code flowchart.
- Hydro addresses (DN 14).
- Remote controller connection changed after address setting.
Who to ask for: Installer / commissioning engineer (Toshiba Estia).
Certification: Manufacturer training advantageous.
On the Estia 5 Series Powerful (Hi Power / Extreme)
- Follow manufacturer's check-code flowchart.
- Rotary switch SW01 address.
Who to ask for: Installer / commissioning engineer (Toshiba Estia).
Certification: Manufacturer training advantageous.
What you might notice
Sources
- Air to Water Heat Pump Service Manual - Wall Mounted Type (File No. AE0-2101W) ↗ · AE0-2101W · page p.114 (printed page; PDF page +1) · Reviewed 23 September 2026
- Hydro Unit Installation Manual EF99812301-4 (Powerful) ↗ · EF99812301-4 · page p.59 (printed page; PDF page +1) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026