MBMap Registry
  1. Devices
  2. Grant
  3. Aerona3 (Chofu)

Grant Aerona3 (Chofu) Modbus register map

Air-to-water heat pump made by Chofu, sold as Grant Aerona3

  • Unofficial
  • 46 registers
  • Modbus RTU
  • Revision 2 · 2026-10-18

Unofficial: Copied from an unofficial source and not tested. Read it as a draft and check a value on the real device before you rely on the rest. Check the map against the manufacturer's documentation before you write to a live device. Tested it? Report a test.

Download .mbmap.json Raw JSON View on GitHub Suggest a correction Report a problem

Communication

Protocol
Modbus RTU
Unit ID
1default
Serial
19200 8N2 · 19200 baud, 8 data bits, none parity, 2 stop bits
Byte / word order
ABCD · bytes big-endian, words high first
Addresses
0-based

Connection values are defaults: the device may be configured differently.

Map

Registers
21 holding registers, 19 input registers, 5 coils, 1 discrete input
Revision
2 · 2026-10-18
Added
()
File
maps/grant/aerona3.mbmap.json · 9 KB · history
SHA-256
699612d37b5ebc4e1a4f9c74824019c1254b15829e1538d642aa8d6590097c48
Manufacturer
grantuk.com

Sources and notes

Source: Warm Energy Labs Heat Pump Modbus Database (MIT licence); draft from reverse engineering, not tested

  • Draft map from reverse engineering in the source; not tested on a device.
  • Writing to a heat pump can damage it: check before you write.
AreaAddressNameTypeAccessUnitScaleDescription
CO 0 bool RW Erase error history
CO 1 bool RW Operation at reboot after blackout: 0=disable, 1=enable
CO 2 bool RW 0=Fixed set point, 1=Climatic curve
CO 6 bool RW Anti-legionella function: 0=disable, 1=enable
CO 7 bool RW HP unit turn on/off based on: 0=Room set point, 1=Water set point
DI 3 bool R Configurable input (terminal 20-21) / heating enable
IR 0 int16 R °C Return water temperature
IR 2 int16 R °C Discharge temperature
IR 5 int16 R °C Defrost temperature
IR 6 int16 R °C Outdoor air temperature
IR 8 int16 R °C Suction temperature
IR 9 int16 R °C Outgoing water temperature
IR 10 int16 R Operating mode: 0=Off, 1=Heating, 2=Cooling
IR 11 int16 R °C ×0.1 Zone 1 room temperature
IR 12 int16 R °C ×0.1 Zone 2 room temperature
IR 13 int16 R DHW mode: 0=Disable, 1=Comfort, 2=Economy, 3=Force
IR 16 int16 R °C DHW tank temperature
IR 20 int16 R % Humidity sensor reading
IR 21 int16 R Current error code
IR 22 int16 R Previous error code 1
IR 23 int16 R Previous error code 2
IR 24 int16 R Previous error code 3
IR 25 int16 R Previous error code 4
IR 26 int16 R Previous error code 5
IR 32 int16 R °C Plate heat exchanger temperature
HR 2 int16 RW °C ×0.5 Fixed outgoing water set point for heating zone 1
HR 3 int16 RW °C ×0.5 Maximum outgoing water temperature for heating zone 1
HR 4 int16 RW °C ×0.5 Minimum outgoing water temperature for heating zone 1
HR 5 int16 RW °C ×0.5 Maximum outdoor air temperature correlation for heating zone 1
HR 6 int16 RW °C ×0.5 Minimum outdoor air temperature correlation for heating zone 1
HR 7 int16 RW °C ×0.5 Fixed outgoing water set point for heating zone 2
HR 8 int16 RW °C ×0.5 Maximum outgoing water temperature for heating zone 2
HR 9 int16 RW °C ×0.5 Minimum outgoing water temperature for heating zone 2
HR 10 int16 RW °C ×0.5 Maximum outdoor air temperature correlation for heating zone 2
HR 11 int16 RW °C ×0.5 Minimum outdoor air temperature correlation for heating zone 2
HR 13 int16 RW °C ×0.5 Fixed outgoing water set point for cooling zone 1
HR 18 int16 RW °C ×0.5 Fixed outgoing water set point for cooling zone 2
HR 26 int16 RW DHW production priority: 0=Standard, 1=Priority
HR 27 int16 RW °C ×0.5 DHW comfort temperature
HR 28 int16 RW °C ×0.5 DHW economy temperature
HR 29 int16 RW °C ×0.5 DHW force temperature
HR 37 int16 RW min Pump run time after compressor off
HR 38 int16 RW Hz Pump frequency setting
HR 39 int16 RW min Compressor start delay
HR 50 int16 RW °C ×0.5 Temperature at which frost protection starts
HR 51 int16 RW °C ×0.5 Temperature at which frost protection stops

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