Heat pumps · Error codes · Hisa Engineering Ltd
E05Hisa Engineering Ltd · Hisa hr290
E05 on a Hisa Engineering Ltd Hisa hr290: High-Pressure Switch One Fault
Short answer
On a Hisa Engineering Ltd heat pump, E05 means: High-Pressure Switch One Fault. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 24 September 2026 · 1 source
What it means
The manual says: High-Pressure Switch One Fault.
Part involved: pressure switch/sensor.
Likely causes:
- 1. High-voltage switch failed 2. Excessive refrigerant 3. Fan doesn’t work typically, or water circulated abnormally 4. Air or other objects mixed into the refrigeration system 5. Too much scale in the water heat exchanger.
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Engineer needed? | Yes |
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 model number on the rating label before contacting your installer.
- Check that the heat pump isolator / consumer-unit breaker is on; do not open any casing.
- A single restart via the controller (off/on) may be tried only if the manual or your installer allows it.
What the engineer will check
- Follow the manufacturer's troubleshooting steps for this code.
- Check the relevant sensor/switch wiring and connectors.
- Measure/replace the component or PCB as indicated.
Who to ask for: F-gas / refrigerant.
What you might notice
Sources
- Hisa R290 Installation & User Manual (300824) ↗ · page 37 · Reviewed 24 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 24 September 2026