LC on a Haier HPM-Nd2 monobloc: Antifreeze protection abnormal

What it means

The manual says: Antifreeze protection abnormal.

Part involved: water flow switch/pump, water temperature.

Likely causes:

• Low temperature leads to prolonged running without defrosting.

Is it safe?

The manual does not say whether the heat pump stops.

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 manufacturer's troubleshooting flowchart for this code.
• 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

• Code shown on the wired controller (and/or the outdoor PCB display); heating/hot water may stop or run on backup heater.

Sources

• Installation and service instructions - HPM08/10/12/14/16-Nd2 (Haier R290 monobloc) ↗ · page p.85 (printed; ManualsLib viewer p.91) · Reviewed 23 September 2026

A code explains what the controller detected, not a confirmed root cause.

Reviewed: 23 September 2026