Specifications

SA Bus Device Limits
The SA Bus is limited to 10 devices total to ensure good communication on the bus and is limited to four NS sensors
because only four unique addresses can be set on the sensors. Due to change of value (COV) limitations, it is best
to limit the number of IOMs on the SA Bus to four. The SA bus is also limited by the total power consumption of the
devices connected on the bus. Exceeding the total power consumption limit can cause poor bus communication and
cause devices to go offline.
Table 9 provides the power consumption of devices commonly connected to the SA bus.
Important: The total power consumption on an SA Bus is limited to 210 mA; do not exceed the SA Bus power
consumption limit. Exceeding the total power consumption limit can cause poor bus communication
and cause devices to go offline.
Table 9: Power Consumption by Common SA Bus Devices
Power Consumption on the SA BusSA Bus Device
12 mADischarge Air Sensors (NS-DTN70x3-0)
12 mABalancing Sensors (NS-DTN70x3-0)
13 mANetwork Sensors without display
21 mANetwork Sensors with display no RH
27 mANetwork Sensors with display and RH
28 mA (non-isolated) or 5 mA (isolated)CO2 Network Sensors (NS-BCN7004-0)
90 mAZFR1811 Wireless Field Bus Router
90 mA - may be a temporary loadDIS1710 Local Controller Display
90 mA - temporary loadWireless Commissioning Converter
NA (self-powered)Variable Speed Drives
NA (self-powered)IOM Series Controllers
NA (self-powered)Romutec® Modules
SA bus applications are limited to a power load of 210 mA.
The best practice when configuring an SA bus is to limit the total available operating power consumption to 120 mA
or less. This power level allows you to temporarily connect a Wireless Commissioning Converter or a DIS1710
Local Controller Display to the bus for commissioning, adjusting, and monitoring.
On SA bus applications where a DIS1710 display or ZFR1811 Wireless Field Bus Router is permanently connected
to the bus, limit the additional available operating power consumption to 30 mA, to allow for the temporary use of a
Wireless Commissioning Converter on the bus.
For example, if the ZFR1811 uses 90 mA and the Wireless Commissioning Converter uses 90 mA, you have 30 mA
available for additional loads: 90 mA + 90 mA + 30 mA = 210 mA total.
28MS/TP Communications Bus Technical Bulletin