d1-03 on a Hisense Hi-Therma Monobloc: Freeze protection (cooling)
Short answer
On a Hisense heat pump, d1-03 means: Freeze protection (cooling). The heat pump keeps running with some functions stopped.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Freeze protection (cooling).
Part involved: water / ambient temperature control.
When it shows: Space Cooling is on and Outlet HP Water Thermistor (TowHP) <=3 C lasting for 100s or Inlet Water Thermistor (Tiw) <=5 C lasting for 100s.
Likely causes:
- Space Cooling is on and Outlet HP Water Thermistor (TowHP) <=3 C lasting for 100s or Inlet Water Thermistor (Tiw) <=5 C lasting for 100s.
Is it safe?
| Does the heat pump stop? | Partly |
|---|---|
| Severity | Information only |
| Engineer needed? | No |
The heat pump keeps running with some functions stopped.
Resetting itself: yes.
What you can check
- Note the code shown on the controller and the unit model numbers (on the rating plate label) before contacting your installer.
- Check the heat pump's breaker/isolator at the consumer unit is on; do not open any casing.
- Check controller mode/temperature/timer settings have not been changed; setup (DIP switch) errors need the installer.
What the engineer will check
- Check cooling setpoints and thermistor readings.
Who to ask for: Heat pump engineer.
Certification: Heat pump installer competence; F-gas / flammable-refrigerant (R290/R32) handling competence for any refrigerant-circuit work.
What you might notice
Sources
- Air-to-Water Heat Pump Technical, Installation and Service Handbook - Hi-Therma Series (TCY12021017E) ↗ · TCY12021017E · page p.334 (printed; ManualsLib viewer p.355) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026