Tech Tips; Bacnet Mstp Best Practice (Eia-485) - Johnson Controls EasyIO FS Series User Manual

Tech tips

If you do not know the device ID, you can use a readDeviceID BACnet wild card command to retrieve the unknown
BACnet device ID. You can use the device MAC address to send the command. You can locate the below objects in
the wiresheet view, where you add the template.
You can switch the temperature sensor unit of the NS8000 or NSA7000 between Celsius and Fahrenheit. To modify
the measurement units, you must find the following objects and write the appropriate values:
Object Name: TemperatureUnit
•
• Object Type: Analog Input 0 (Zone Temperature)
• Property Type: Units (Enum data type)
Value: 62 (Celsius) or 64 (Fahrenheit)
•
• Object Name: MinSetPoint
Object Type: Analog Value 0 (Zone Temperature Setpoint)
•
Property Type: Min_Press_Value (Numeric data type)
•
• Value: Min Temperature set point value for Celsius or Fahrenheit
Object Name: MaxSetPoint
•
• Object Type: Analog Value 0 (Zone Temperature Setpoint)
• Property Type: Max_Press_Value (Numeric data type)
Value: Max Temperature Set point value for Celsius or Fahrenheit
•
You can use MinSetPoint and MaxSetPoint to restrict the set point range. There are also templates in CPT Tools.
You must ensure that you update CPT Tools to the latest build, which comes with the Sedona 2.0 framework
upgrade along with the SA Bus device templates.

BACnet MSTP best practice (EIA-485)

You can refer to the following best practices for the BACnet MSTP wiring guide:
• Do not run the MSTP bus cable across or near any high voltage cables.
• EIA-485 requires three conductors, which are wire or cable. These conductors are TX, RX, and Gnd. The
Gnd conductor is not ground or earth. Therefore, do not connect the conductor to the ground. The third
conductor is a reference signal for both TX and RX. The TX and RX voltage is measured relative to the Gnd
conductor. If you connect it to the ground, it causes an incorrect voltage and might damage the
transceiver.
• You must use the correct cables in terms of impedance. You must choose low impedance cables and run
100 Ohms/120 Ohms impedance cables.
• You must run Belden Twisted Shielded Pair cables, model number Belden 3106A. If this model is not
available, any equivalent brand with the same characteristics is valid. You must ensure that the cables are