Heat pumps · Error codes · Hisense
78Hisense · Hi-Therma Monobloc (R32)
78 on a Hisense Hi-Therma Monobloc: Hydraulic flow abnormality alarm (WP1)
Short answer
On a Hisense heat pump, 78 means: Hydraulic flow abnormality alarm (WP1). 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: Hydraulic flow abnormality alarm (WP1).
Part involved: water pressure, pump WP1, flow, freeze protection.
Likely causes:
- Water flow is detected abnormality in the hydraulic cycle.
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