Heat pumps · Error codes · Grant
750Grant
750 on a Grant heat pump: Slave Remote controller communication error
Short answer
On a Grant heat pump, 750 means: Slave Remote controller communication error. The manual does not say whether the heat pump stops. An engineer is needed to fix the cause.
Reviewed 23 September 2026 · 2 sources
What it means
The manual says: Slave Remote controller communication error.
Part involved: slave remote controller / controller PCB.
Likely causes:
- Incorrect slave remote controller wiring or DIP SW setting.
- Loose interface connection cable or contacts.
- Slave remote controller faulty.
- PCB(Controller) faulty.
Is it safe?
| Does the heat pump stop? | Not stated |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The manual does not say whether the heat pump stops.
Resetting itself: Yes (Chofu 'Auto').
Manual reset: Not required (auto).
What you can check
- Note the exact code shown on the controller display and tell your installer or Grant-trained engineer.
- Grant advises homeowners NOT to reset Aerona3 fault codes themselves - leave the reset to the engineer.
What the engineer will check
- Check loose cable connections and contacts and DIP SW (back of remote controller); correct and restart.
- Otherwise replace slave remote controller or controller PCB.
Who to ask for: Grant-trained heat pump engineer.
What you might notice
What owners and engineers report
9 owner and engineer reports mention this.
- Controller / thermostat problem on the Aerona³ R32: 9 reports
Sources
- Chofu Service Manual AEYC-0643XU-CH / 1043XU-CH / 1242XU-CH / 1643XU-CH (RA-98(5)) - Air to Water Heat Pump, Monobloc DC Inverter ↗ · RA-98(5) · page 31 · Reviewed 23 September 2026
- Chofu AEYC-0639U-CH / AEYC-1039U-CH / AEYC-1639U-CH Installation and Instruction Manual (R410A) ↗ · Chofu AEYC-0639U/1039U/1639U-CH Installation and Instruction Manual (ManualsLib-derived copy) · page 146 · Reviewed 23 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 23 September 2026