28 on a Kingspan Aeromax Plus air-to-water monobloc: Discharge temperature error (failure / out of range)
Short answer
On a Kingspan heat pump, 28 means: Discharge temperature error (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: Discharge temperature error (failure / out of range).
Part involved: Compressor discharge.
Likely causes:
- Discharge gas too hot - e.g. low refrigerant charge, restriction.
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.
- Check the outdoor unit is not blocked by leaves, snow or debris.
What the engineer will check
- Check refrigerant charge/leaks, expansion device, TD sensor.
Who to ask for: refrigeration / heat pump engineer.
Certification: F-gas certification (refrigerant circuit work) and electrical competence.
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