15 on a Kingspan Aeromax Plus air-to-water monobloc: Exit (leaving) water temperature sensor (LWT) failure / out of range
Short answer
On a Kingspan heat pump, 15 means: Exit (leaving) water temperature sensor (LWT) failure / out of range. 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: Exit (leaving) water temperature sensor (LWT) failure / out of range.
Part involved: LWT thermistor.
Likely causes:
- Sensor open/short or out of range.
Is it safe?
| Does the heat pump stop? | Yes |
|---|---|
| Severity | Fault — needs a manual reset once the cause is fixed |
| Engineer needed? | Yes |
The heat pump stops until the fault clears or is reset.
Resetting itself: Manual: after the error has been cleared, reset by turning off the mains supply for 10 seconds and on again.
What you can check
- Note the code/LED pattern and the model from the rating plate, then contact a heat pump/refrigeration engineer.
- Check the heat pump's breaker/isolator at the consumer unit is on.
What the engineer will check
- Check LWT thermistor and wiring.
Who to ask for: refrigeration / heat pump engineer.
Certification: Electrical competence for work inside the unit.
What you might notice
Sources
- Kingspan Aeromax Plus Air Source Heat Pump Installation and Maintenance Manual (KHP0041/38/39/40/42), A9317C Ver 1.2b ↗ · A9317C Ver 1.2b · page 24 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026