L15 on a Toshiba heat pump: Combination failure
Short answer
On a Toshiba heat pump, L15 means: Combination failure. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause. The wording differs by model range — each is shown below.
Reviewed 23 September 2026 · 4 sources
What it means
On the R32 Estia 1-Series (split, Wall-Mounted and All-in-One)
The manual says: Combination failure.
Part involved: DIP switches, DN/FC codes, addresses, model combination.
When it shows: Hydro unit model name differs (detected by outdoor unit).
Likely causes:
- Hydro unit model.
- DN 6BD setting.
On the Estia (Series 4) Standard & Powerful
The manual says: Combination error - model code of hydro unit is different (Powerful type only).
Part involved: DIP switches, DN/FC codes, addresses, model combination.
When it shows: Model name of the outdoor unit is different.
Likely causes:
- Outdoor unit model.
On the Estia 5 Series (Standard)
The manual says: Combination error.
Part involved: DIP switches, DN/FC codes, addresses, model combination.
When it shows: Model name of the outdoor unit is different.
Likely causes:
- Outdoor unit model.
On the Estia 5 Series Powerful (Hi Power / Extreme)
The manual says: Combination error - model name of the hydro unit is different (outdoor detected).
Part involved: DIP switches, DN/FC codes, addresses, model combination.
Likely causes:
- Hydro unit model.
- DP_SW13_4 ON.
Is it safe?
On the R32 Estia 1-Series (split, Wall-Mounted and All-in-One)
| 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.
On the Estia (Series 4) Standard & Powerful
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump keeps running with some functions stopped.
Resetting itself: no.
Manual reset: Cause must be fixed by an engineer; hardware faults reappear until repaired.
On the Estia 5 Series (Standard)
| 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.
On the Estia 5 Series Powerful (Hi Power / Extreme)
| 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 unit model.
- DN 6BD setting.
Who to ask for: Installer / commissioning engineer (Toshiba Estia).
Certification: Manufacturer training advantageous.
On the Estia (Series 4) Standard & Powerful
- Follow manufacturer's check-code flowchart.
- Outdoor unit model.
Who to ask for: Installer / commissioning engineer (Toshiba Estia).
Certification: Manufacturer training advantageous.
On the Estia 5 Series (Standard)
- Follow manufacturer's check-code flowchart.
- Outdoor unit model.
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.
- Hydro unit model.
- DP_SW13_4 ON.
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.116 (printed page; PDF page +1) · Reviewed 23 September 2026
- Quick Reference Air to Water Heat Pump Series 4 Standard & Powerful Types ↗ · Quick Reference Series 4 Standard & Powerful (undated) · page p.62 (printed page; PDF page +1) · Reviewed 23 September 2026
- Air to Water Heat Pump Service Manual (File No. A10-1704) - Estia 5 Series Indoor/Outdoor ↗ · A10-1704 · page p.91 (printed page; PDF page +1) · Reviewed 23 September 2026
- Hydro Unit Installation Manual EF99812301-4 (Powerful) ↗ · EF99812301-4 · page p.60 (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