76 on a Hisense Hi-Therma Monobloc: Freeze Protection Stop by indoor unit temperature thermistors
Short answer
On a Hisense heat pump, 76 means: Freeze Protection Stop by indoor unit temperature thermistors. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 1 source
What it means
The manual says: Freeze Protection Stop by indoor unit temperature thermistors.
Part involved: water pressure, pump WP1, flow, freeze protection.
When it shows: Water temperature or refrigerant temperature is too low and trigger freezing protection.
Likely causes:
- Water temperature or refrigerant temperature is too low and trigger freezing protection.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: unknown.
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 the heating system pressure gauge shows the pressure your installer set (typically about 1-2 bar); if it is low, report it rather than refilling unless you have been shown how. Check any filling loop is closed.
- Check radiator valves / underfloor zones are open and thermostats are calling for heat.
- In freezing weather keep the heat pump powered on (its frost protection relies on power) and check the outdoor unit is clear of snow/ice.
What the engineer will check
- Follow the handbook alarm-code flowchart (O.U. section from printed p.335, I.U. section from viewer p.383).
- Check water pressure, strainer/filter and air in the system.
- Check circulation pump operation and flow sensor/switch.
- Check heater safety thermostats and wiring.
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