PA on a Haier HPM-Nd2 monobloc: AC input undervoltage, open phase protection, input power abnormal or compressor reversal
Short answer
On a Haier heat pump, PA means: AC input undervoltage, open phase protection, input power abnormal or compressor reversal. 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: AC input undervoltage, open phase protection, input power abnormal or compressor reversal.
Part involved: compressor, inverter/driver PCB, power supply.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| 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.
- If the breaker or RCD trips repeatedly, leave the heat pump switched off and call an engineer; do not keep resetting it.
What the engineer will check
- Follow the manufacturer's troubleshooting flowchart for this code.
- Check supply voltage and phase balance.
- Check compressor windings and inverter/driver PCB per flowchart.
- Check heat-sink cooling and connections.
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
- Installation and service instructions - HPM08/10/12/14/16-Nd2 (Haier R290 monobloc) ↗ · page p.86 (printed; ManualsLib viewer p.92) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026