Design considerations - Johnson Controls - LIT-12014420 - RA-1270 - Airflow Measuring Station - AFMS

RA-1270 Fan Inlet Airflow and Temperature Measurement Station SA Bus Integration Application Note

Product name
AFMS
Document type
Application Note
Document number
LIT-12014420
Revision date
2024-05-17

When you integrate the RA-1270 device, consider the following guidelines:

  • Install all RA-1270 equipment and ensure that the RA-1270 device is set up and operates correctly before you attempt to integrate the RA-1270 device into the GSAB network.
    Note: The correct operation of RA-1270 equipment is the responsibility of a Johnson Controls representative.
  • Ensure to set all device addresses on each RA-1270 device. Avoid SA Bus reserved addresses 0 to 3. Do not change the device address when you add the associated GSAB device in the CCT tool. For more information, refer to the RA-1270 Fan Inlet Airflow and Temperature Measurement Station Installation Guide (Part No. A16381BYDU).
  • The communication parameters on the SA Bus are fixed. Ensure to set the following values on each RA-1270 device:
    • 38,400k baud
    • 8 data bits
    • No parity
    • 1 stop bit
  • The SA Bus is an RS-485 daisy-chain topology network that supports connections of up to 10 devices. Traffic considerations and power consumption can reduce that amount. The total power consumption for the SA Bus is limited to 240 mA on the SA Bus terminal block. If the total power consumption exceeds this limit, it may result in poor bus communication and cause devices to go offline.
  • Ensure you have the correct JCPKG file that represents the specific BACnet MS/TP device. The JCPKG file includes the point list for a specific BACnet MS/TP device. The CCT tool and the JCPKG file add the device to the application when you configure the Equipment Controller.
    Note: You cannot configure GSAB integration without the device-specific JCPKG file.
  • Follow the SA Bus rules in the MS/TP Communications Bus Technical Bulletin (LIT-12011034).
  • Apply CCT Release Mode 10.7/Firmware 11.0 or higher when you create the CAF file.
  • If necessary, and if possible, set the Max Master parameter on the RA-1270 device to an appropriate value to avoid additional latency on the SA Bus.