E16 on a Grant Aerona 290: DC bus voltage is too high
Short answer
On a Grant heat pump, E16 means: DC bus voltage is too high. 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: DC bus voltage is too high.
Part involved: refrigerant & drive PCB / compressor.
Likely causes:
- Cables incorrectly connected.
- Refrigerant & Drive PCB is faulty.
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: Not stated in DOC 0204.
Manual reset: DOC 0204 s11.1: once the fault is resolved, reset by turning the unit OFF and back ON; s11.5: power cycle can be done from the Aerona Smart Controller touchscreen instead of the external isolator (installer procedure).
What you can check
- Note the exact code shown on the controller display and tell your installer or Grant-trained engineer.
- Check the heat pump isolator switch and the consumer-unit breaker/RCD for the heat pump are ON (do not repeatedly reset a tripping breaker).
What the engineer will check
- Check all connections from the Refrigerant PCB (or Refrigerant & Drive PCB for the 15.5 kW model); ensure made correctly.
- Check the Refrigerant PCB (or Refrigerant & Drive PCB for 15.5 kW); replace if faults remain.
Who to ask for: Grant-trained heat pump engineer with inverter/electrical competence.
Certification: Competent electrician/heating engineer for mains electrical and PCB work (safe isolation; capacitor discharge).
What you might notice
Sources
- Grant Aerona 290 Air to Water Air Source Heat Pump Range - Installation & Operating Instructions (UK DOC 0204) ↗ · Rev 1.9 · page 56 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026