Heat pumps · Error codes · Hisa Engineering Ltd
E03Hisa Engineering Ltd · Hisa hr290
E03 on a Hisa Engineering Ltd Hisa hr290: Outside Water Flow Switch Fault
Short answer
On a Hisa Engineering Ltd heat pump, E03 means: Outside Water Flow Switch 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: Outside Water Flow Switch Fault.
Part involved: water flow / pump.
Likely causes:
- 1. Circulating pump failed, or water system blocked 2. Water flow switch failed, or opposite installed direction 3. The lift of the circulating pump is not enough 4. Circulating pump has opposite installed direction.
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 and check the heating system pressure gauge reading (typically 1-2 bar when cold) and tell your installer if it is low.
- Check that the heat pump isolator / consumer-unit breaker is on and the outdoor unit is not blocked by debris or snow.
- Do not open the unit or top up the system yourself unless your installer has shown you how to use the filling loop; make sure the filling loop is closed afterwards.
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: heating / hydraulic.
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