A2 on a Grant heat pump: Protective action against excess Current DC current detection
Short answer
On a Grant heat pump, A2 means: Protective action against excess Current DC current detection. The heat pump stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 2 sources
What it means
The manual says: Protective action against excess Current DC current detection.
Part involved: compressor / main PCB.
When it shows: Detected by heat pump/controller PCB; error reset type printed as 'Manual'.
Likely causes:
- Unreasonable operation under overload (blocked air inlet/outlet, excess gas).
- Drop of power voltage.
- Main PCB faulty.
- Momentary stop of power (lightning).
- Compressor 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: No.
Manual reset: Manual: engineer presses - and + on the remote controller together for 3 s, or Reset SW on the Terminal PCB (mains OFF/ON possible but not recommended).
What you can check
- Note the exact code shown on the controller display and tell your installer or Grant-trained engineer.
- Check the outdoor unit air inlet and fan outlet are not blocked by leaves, snow, ice or stored objects.
- 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).
- Grant advises homeowners NOT to reset Aerona3 fault codes themselves - leave the reset to the engineer.
What the engineer will check
- Check the place of installation for blockage of air inlet & outlet.
- Check the excess gas; if observed collect all refrigerant and recharge with prescribed mass.
- Check power voltage (230V).
- Operate without the junction connector of compressor lead wire - if same code reappears replace Main PCB.
- Restart after momentary power loss.
- Otherwise replace compressor.
Who to ask for: Grant-trained (G1) heat pump engineer.
Certification: F-gas certified refrigeration engineer (refrigerant circuit work).
What you might notice
What owners and engineers report
7 owner and engineer reports mention this.
- No heating on the Aerona³ R32: 5 reports
- Keeps stopping / cutting out on the Aerona³ R32: 1 report
- No heating on the Aerona³ (R410A): 1 report
Sources
- Grant Aerona³ Air to Water High Efficiency Heat Pump Range - Installation and Servicing Instructions (UK DOC 0136) ↗ · Rev 2.4 · page 54 (DOC 0154: 53) · Reviewed 23 September 2026
- Grant UK Aerona³ Air to Water High Efficiency Heat Pump Range - Installation and Servicing Instructions (UK DOC 0109) ↗ · Rev 1.1 · page 53 (IRL DOC 0001: s11.4-11.5, printed pp55-57) · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026