Gree AC Modbus RTU ESPHome Component

ESPHome external component for controlling Gree commercial AC units via RS485 Modbus RTU.

Tested Hardware

• AC Unit: Gree U-Match series duct unit
• Controller: ESP32 / ESP8266 with RS485 transceiver (MAX485 or similar)
• Connection: COM-BMS (CN3) daughter board on the indoor unit

Features

• Full climate control (On/Off, Mode, Temperature, Fan Speed)
• Temperature reading from indoor unit sensor
• Outdoor temperature sensor (optional)
• Vertical and horizontal swing control (via selects for granular positions)
• Sleep mode, Turbo mode, Fresh air valve switches
• 5 fan speeds + Auto + Turbo
• Expose Sensors toggle — publishes every state value as its own sensor
• Current Temp Source select — choose which register feeds the climate's current temperature (wired controller, IDU return air, return-air port, light board)
• Debug mode — dumps all registers 0–92 as a JSON text sensor for reverse engineering, plus an optional register read/write interface

Wiring

Connect your RS485 transceiver to the COM-BMS / CN3 board:

• A+ (Data+)
• B- (Data-)
• GND (I used the metal chassis of the indoor unit)

UART settings: 9600 baud, 8N1

RS485 Module Types

Auto-direction modules (recommended): These modules automatically switch between TX and RX modes. Just connect VCC, GND, TX, and RX - no additional GPIO needed.

MAX485 modules (with DE/RE pins): These require manual direction control. Wire DE and RE together to a GPIO pin and configure flow_control_pin in your YAML:

ESP32          MAX485
GPIO17  -----> DI
GPIO16  <----- RO
GPIO4   -----> DE + RE (directly connect or jumper together. Try only RE first - might work)
3.3V    -----> VCC
GND     -----> GND

Installation

Add to your ESPHome YAML:

external_components:
  - source: github://sgtaziz/esphome_gree_modbus
    components: [gree_ac]

Configuration

See example.yaml for a complete configuration example.

Minimal Configuration

uart:
  tx_pin: GPIO17
  rx_pin: GPIO16
  baud_rate: 9600

climate:
  - platform: gree_ac
    name: "Gree AC"

Full Configuration

uart:
  tx_pin: GPIO17
  rx_pin: GPIO16
  baud_rate: 9600

climate:
  - platform: gree_ac
    name: "Gree AC"
    slave_id: 1
    update_interval: 5s
    flow_control_pin: GPIO4  # Optional: only for MAX485 modules
    outdoor_temperature:
      name: "Outdoor Temperature"
    vertical_swing_select:
      name: "Vertical Swing"
    horizontal_swing_select:
      name: "Horizontal Swing"
    sleep_switch:
      name: "Sleep Mode"
    turbo_switch:
      name: "Turbo Mode"
    fresh_air_switch:
      name: "Fresh Air"

Expose Sensors

Set expose_sensors: true to publish each state value as a separate sensor (named "<climate name> <label>"). Useful for logging and troubleshooting.

climate:
  - platform: gree_ac
    name: "Gree AC"
    expose_sensors: true

This creates sensors for: Set Point, Current Temperature, Mode, Fan Speed, Power State, Sleep, Turbo, Fresh Air, Contamination, Set Temperature Precise, Ambient Return Air, and Ambient Light Board. (Outdoor temperature already has its own outdoor_temperature: key, so it is not duplicated here.)

Current Temperature Source

Some installations have multiple temperature sensors. Use current_temp_source to pick which register feeds the climate's current_temperature:

climate:
  - platform: gree_ac
    name: "Gree AC"
    current_temp_source:
      name: "Current Temp Source"

Options (selectable from Home Assistant):

Option	Register	Scaling
Wired Controller	3	÷10, signed (default)
IDU Return Air	4	÷1
Return Air Port	82	÷10, signed
Light Board	83	÷10, signed

Switching the source updates current_temperature instantly from the cached register values (no waiting for the next poll).

Debug Mode

Enable debug_mode: true to sweep every register 0–92 and publish the values as a JSON text sensor (e.g. {"0":1234,"1":null,...}). Registers the unit does not support show as null, which makes it easy to map out what exists.

climate:
  - platform: gree_ac
    name: "Gree AC"
    debug_mode: true

To also write registers (e.g. to probe writeable addresses), enable debug_write: true. This adds three entities: a register-address number (0–92), a register-value number (0–65535), and a write button. Setting both numbers and pressing the button writes that value to the unit using Modbus function 0x10. debug_write implies debug_mode.

⚠️ Debug writes go straight to the AC with no guardrails. They are logged at WARNING level. Use at your own risk — writing the wrong register can change unit behavior.

Modbus Registers

Key registers used:

Register	Description
2	On/Off (85=Off, 170=On)
3	Current temperature × 10 (wired controller sensor; default current-temp source)
4	Ambient temperature (IDU return air sensor)
5	IDU Address
17	Mode (1=Cool, 2=Heat, 3=Dry, 4=Fan, 5=Auto)
19	Fan Speed (0=Auto, 1-5=Speed, 6=Turbo)
20	Set Temperature (whole degrees)
22	Vertical Swing
23	Horizontal Swing
24	Fresh Air Valve
25	Sleep Mode
34	Contamination grade
39	Ambient temp sensor selection
42	Set Temperature × 10 (0.5°C precision, read-only)
49	Outdoor Temperature
77	DRED function
82	Ambient temp at return air port × 10
83	Ambient temp of light board × 10

Use debug_mode: true to sweep and inspect all registers 0–92.