Understanding RS485 and Modbus in Braemar Ducted Reverse Cycle Systems with Third-Party Control

  1. RS485 and Modbus Basics:

    • RS485: A hardware standard used for communication in electronics.
    • Modbus: A software protocol that operates over RS485 hardware.

  2. Keypad and Central Control:

    • Models (SDHV, KDHV, Dominator) use RS485 for their keypads (H1/H2). The software is proprietary to Braemar /Gree.
    • Third-party controls connect through a central control RS485 port, not the keypad port.

  3. New Model (KDHA):

    • Uses HBS for keypad control, which is proprietary to Braemar /Gree.
    • Comes with a central control gateway (a small circuit board) for RS485-Modbus connection.

  4. Third-Party Control Methods:

    • Airtouch:
      • SDHV 1-phase: Uses Modbus (umatch5 register list) with S2 dip switch set to 0010.
      • SDHV 3-phase: Uses Modbus (VRF register list) with S2 dip switch set to 0110.
      • KDHV 1-phase: Uses Modbus (umatch5 register list) with S2 dip switch set to 0010.
      • KGHV 1-phase: Uses Modbus (umatch5 register list) with S2 dip switch set to 0010.
      • SDHS 3-phase: Uses Modbus (umatch6/VRF list) with S2 dip switch set to 0110.
      • KDHA 1-phase: Uses Modbus (umatch6/VRF list) with S2 dip switch set to 0110.
    • Izone:
      • SDHV 1-phase: Uses Modbus (umatch5 register list).
      • SDHV 3-phase: Not compatible (VRF register list).
      • KDHV 1-phase: Uses Modbus (umatch5 register list).
      • KGHV 1-phase: Uses Modbus (umatch5 register list).
      • SDHS 3-phase: Not compatible (umatch6/VRF list).
      • KDHA 1-phase: Not compatible (umatch6/VRF list).
    • MyAir:
      • SDHV 1-phase: Uses H1/H2 RS485 (mimics keypad).
      • SDHV 3-phase: Uses HBS (not compatible).
      • KDHV 1-phase: Uses H1/H2 RS485 (mimics keypad).
      • KGHV 1-phase: Uses H1/H2 RS485 (mimics keypad).
      • SDHS 3-phase: Uses HBS (not compatible).
      • KDHA 1-phase: Uses HBS (not compatible).

  5. Important Notes:

    • Modbus can only send commands to the unit but cannot report the room temperature. The return air sensor must be used for accurate temperature readings.
    • In heating mode, if the roof space is warm, the unit might falsely read the temperature and not start the fan.
    • Future updates for Airtouch might change how it connects, potentially avoiding the temperature reading issue.