I have an Alliance Heat Pump with a wired control panel. Alliance seems to be rebranding Midea units.
After sniffing the communication lines with a logic analyzer, I saw that it's a differential pair, like RS485. The request and answer frames start with 0xAA and end with 0x55. Searching for this I stumbled upon: https://codeberg.org/xye/xye
My heat pump's format is however slightly different, but the basics helped to find the correct decoding formula for temperatures. A 24h dump of raw data with my attempt at decoding the frames can be found in this LibreOffice spreadsheet.
I programmed an ESP32 to listen to the RS485 bus and log all frames to MQTT. The firmware is available in the firmware directly in the repository. I write the data to Influxdb and plot the values using Grafana.
Model KJR-26B or SUNI-W/H-002
| Code | Colour | Purpose |
|---|---|---|
| AC10V | White | 10Vac supply |
| AC10V | Red | 10Vac supply |
| P | Brown | RS485 B- |
| Q | Black | RS485 A+ |
| E | Yellow | Earth/Ground/0V |
| Byte Nr | Purpose |
|---|---|
| 0x00 | Header. Always 0xAA. |
| 0x01 | 8 = schedule off, 0 = schedule on, 0x82 = ?? becomes this when status byte 4 is 0x88 |
| 0x02 | 0xFF |
| 0x03 | 0x00 |
| 0x04 | 0x00 |
| 0x05 | Tank Temp Setting |
| 0x06 | Temp Diff Setting |
| 0x07 | 0x00 |
| 0x08 | 0=??, 1=?? - seen as 1 at start of schedule on |
| 0x09 | 0x00 |
| 0x0A | 0x00 |
| 0x0B | 0 = e-heat disabled, 0x01 = e-heat enabled |
| 0x0C | 0x00 |
| 0x0D | 0x00 |
| 0x0E | 0x00 |
| 0x0F | 0x00 |
| 0x10 | 0x00 |
| 0x11 | 0x00 |
| 0x12 | 0x00 |
| 0x13 | 0x28 |
| 0x14 | 0x00 |
| 0x15 | 0x00 |
| 0x16 | 0x00 |
| 0x17 | 0x00 |
| 0x18 | 0x00 |
| 0x19 | 0x00 |
| 0x1A | 0x00 |
| 0x1B | 0x00 |
| 0x1C | 0x00 |
| 0x1D | 0x00 |
| 0x1E | Checksum = 256 - (sum(b1:b29)%256) |
| 0x1F | 0x55 |
| Byte Nr | Purpose |
|---|---|
| 0x00 | Header. Always 0xAA. |
| 0x01 | 0x01 |
| 0x02 | 0x00 |
| 0x03 | 0xFF |
| 0x04 | 0x08 = schedule off, 0x82 = schedule on, 0x88 = ?? after this command byte 1 becomes 0x82 |
| 0x05 | 0x08 |
| 0x06 | 0x00 |
| 0x07 | 0x00 |
| 0x08 | T1 = byte/2 - 0x0F = outlet water temperature |
| 0x09 | 0x00 = pump off, 0x64 = pump on (100%?) |
| 0x0A | 0x00 |
| 0x0B | 0x00 |
| 0x0C | 0x00 except 0x20 when byte 4 is 0x82 |
| 0x0D | 0x00 |
| 0x0E | T3 = byte/2 - 0x0F = evaporator temperature |
| 0x0F | 0x00 |
| 0x10 | Ia - pump amps? |
| 0x11 | 0x00 |
| 0x12 | 0x3C |
| 0x13 | 0x28 |
| 0x14 | 0x00 = pump off, 0x20,0x22,0x24 = pump on - related to current temp diff |
| 0x15 | 0x00 |
| 0x16 | T5 = byte/2 - 0x0F = tank temperature |
| 0x17 | T4 = byte/2 - 0x0F = environment temperature |
| 0x18 | 0x01 |
| 0x19 | 0x00 = pump off, 0x01 = pump on |
| 0x1A | 0x00 |
| 0x1B | 0x00 |
| 0x1C | Tank Temp Setting - follows command byte 0x05 |
| 0x1D | Command check = 0xFF - byte 0x01 |
| 0x1E | Checksum = 256 - (sum(b0x01:b0x1D)%256) |
| 0x1F | 0x55 |