E38 on a Haier Super Aqua R290 Hydro Split / Hydro All-in-One: High Pressure Over Low Protection

What it means

The manual says: High Pressure Over Low Protection.

Part involved: compressor, pressure switch/sensor, expansion valve, refrigerant charge.

When it shows: Pd_temp≤ Ps corrected Pd_temp+1°C for 5 minutes, and the fault was cleared after 3 minutes. If it occurs 3 times in an hour, confirm the failure.

Is it safe?

The heat pump stops until the fault clears or is reset.

Resetting itself: yes (until locked).

Manual reset: Locks out after repeated occurrences (see manual remark); engineer reset after the cause is fixed.

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 outdoor unit is not blocked by leaves, debris, snow or ice and that nothing is stored against the grilles.

What the engineer will check

• Follow the manufacturer's troubleshooting flowchart for this code.
• Check refrigerant pressures and charge (F-gas / flammable refrigerant competent person only).
• Check expansion valve, pressure switches/sensors and discharge temperature.
• Check outdoor coil airflow and blockages.

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

• R290 Super Aqua Hydro Split & Hydro All in One Service Manual - Service Diagnosis (SYJS-03-2024 REV.A) ↗ · SYJS-03-2024 REV.A · page p.46 (printed; PDF p.4) · Reviewed 23 September 2026

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

Reviewed: 23 September 2026