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Specifications Specifications 4/1/2022
Products: AS-B
Functionalities: Engineering, Hardware
Product version: 1.8





At the core of a SmartStruxure solution is a SmartStruxure server device, such as AS-B. AS-B performs key functionality, such as control logic, trend logging, and alarm supervision, provides built-in I/O, and supports communication and connectivity to the field buses. The distributed intelligence of the SmartStruxure solution ensures fault tolerance in the system and provides a fully featured user interface through WorkStation and WebStation.


AS-B is a powerful device with built-in power supply and I/O. AS-B can act as a standalone server using its built-in I/O and also monitor and manage field bus devices. In a small installation, the embedded AS-B device acts as a standalone server, mounted in a small footprint. In medium and large installations, functionality is distributed over multiple SmartStruxure server devices that communicate over TCP/IP.

Communications hub

Capable of coordinating traffic from above and below its location, AS-B can deliver data directly to you or to other servers throughout the site. AS-B can run multiple control programs, manage built-in I/O, alarms, and users, handle scheduling and logging, and communicate using a variety of protocols. Because of this, most parts of the system function autonomously and continue to run as a whole even if communication fails or individual SmartStruxure servers or devices go offline.


AS-B comes in four models with different I/O point count and I/O mix.


I/O Points









AS-Bs with “H” in the product name are equipped with a display for output override.

AS-Bs with 36 I/O points have the same small footprint as AS-Bs with 24 I/O points, but with 50 percent higher I/O point count.

Versatile and flexible mix of I/O points

AS-B offers a mix of I/O point types that match most types of HVAC applications. Most I/O points are highly flexible and can be configured as either inputs or outputs.

AS-Bs with 24 I/O points have the following types:

  • 12 Universal inputs/outputs, Ua type

  • 4 Universal inputs/outputs, Ub type

  • 4 Digital inputs

  • 4 Relay outputs

AS-Bs with 36 I/O points have the following types:

  • 20 Universal inputs/outputs, Ua type

  • 8 Universal inputs/outputs, Ub type

  • 4 Triac outputs

  • 4 Relay outputs

Universal inputs/outputs

The universal inputs/outputs are ideal for any mix of temperature, pressure, flow, status points, and similar point types in a building control system.

The universal inputs/outputs can be configured to read several different types of inputs:

  • Digital

  • Counter

  • Supervised

  • Voltage

  • Current (Ub only)

  • Temperature

  • Resistive

  • 2-Wire RTD temperature

  • 2-Wire RTD resistive

As counter inputs, the universal inputs/outputs are commonly used in energy metering applications. As RTD inputs, they are ideal for temperature points in a building control system. As supervised inputs, they are used for security applications where it is critical to know whether or not a wire has been cut or shorted. These events provide a separate indication of alarms and events in the system.

For all analog inputs, maximum and minimum levels can be defined to automatically detect over-range and under-range values.

The universal inputs/outputs are capable of supporting analog outputs of type voltage outputs. Therefore, the universal inputs/outputs support a wide range of devices, such as actuators.

Digital inputs

The digital inputs can be used for cost effective sensing of multiple dry contact digital inputs in applications, such as equipment status monitoring or alarm point monitoring. As counter inputs, digital inputs are commonly used in energy metering applications.

Relay outputs

The relay outputs support digital Form A point types. The Form A relays are designed for direct load applications.

Triac outputs

The triac outputs can be used in many applications to switch 24 VAC on or off for external loads such as actuators, relays, or indicators. Triacs are silent and do not suffer from relay contact wear.

Manual override function

AS-Bs with “H” in the product name are equipped with an LCD display and keys to support manual override control of analog and digital outputs. This function allows you to manually override the outputs for testing, commissioning, and maintenance of equipment.

The override configuration is readable through user interfaces, such as Building Operation WorkStation, enabling more precise monitoring and control.

Built-in power supply

The device has a built-in power supply designed to accommodate 24 VAC or 24 VDC input power. The main AC/DC input (L/+ and N/-) is galvanically isolated from the electronics. This removes the risk of damage due to earth currents and permits the input power to be wired without concern for polarity matching.

Variety of connectivity options

AS-B has numerous ports that enable it to communicate with a wide range of protocols, devices, and servers.

AS-B has the following ports:

  • Two 10/100 Ethernet ports

  • One RS-485 port

  • One USB host port

  • One USB device port

The two Ethernet ports are connected to a built-in Ethernet switch. One port should be connected to the site network. The other port can be used to connect a single WorkStation or WebStation, a Modbus TCP unit, or a BACnet/IP device, but not another SmartStruxure server.

The USB device port allows you to upgrade and interact with AS-B using Device Administrator. The USB host port can be used to provide power and communications for AD.

Authentication and permissions

A SmartStruxure solution provides a powerful permission system that is easy to manage, flexible, and adapts to all kinds of system sizes. The permission system provides a security level to the highest standards. Authentication is done against the built-in user account management system or against Windows Active Directory Domains. The built-in account management system allows an administrator to set password policies that meet stringent CyberSecurity guidelines. When Windows Active Directory is used, the administration costs are lower because users do not have to be managed in multiple directories.

WorkStation/WebStation interface

Through any client, the user experience is similar regardless of which SmartStruxure server the user is logged on to. The user can log directly on to AS-B to engineer, commission, supervise, and monitor AS-B and its built-in I/O as well as its attached field bus devices. See the WorkStation and WebStation specification sheets for additional information.

Open building protocol support

One of the cornerstones of SmartStruxure solution is support for open standards. AS-B can natively communicate with two of the most popular standards for buildings: BACnet and Modbus.

Native BACnet support

AS-B communicates directly to BACnet/IP and BACnet MS/TP networks. AS-B provides access to an extensive range of BACnet devices from Schneider Electric and other vendors.

Native Modbus support

AS-B natively integrates Modbus RS-485 master and slave configurations, as well as Modbus TCP client and server. This allows full access to third-party products and the range of Schneider Electric products that communicate on the Modbus protocol, such as power meters, UPS, circuit breakers, and lighting controllers.

Web Services support

AS-B supports the use of Web Services based on open standards, such as SOAP and REST, to consume data into the SmartStruxure solution. Use incoming third-party data (temperature forecast, energy cost) over the Web to determine site modes, scheduling, and programming.

EcoStruxure Web Services support

EcoStruxure Web Services, Schneider Electric’s Web Services standard, is natively supported in AS-B. EcoStruxure Web Services offers extra features between compliant systems whether within Schneider Electric or other authorized systems. These features include system directory browsing, read/write of current values, alarm receipt and acknowledgement, and historical trend log data. EcoStruxure Web Services is secure. User name and password are required to log on to the system.

Two programming options

Unique to the industry, AS-B has both Script and Function Block programming options. This flexibility assures that the best programming method can be selected for the application.

eMMC memory for data and backup

The SmartStruxure server device has a 4 GB eMMC memory, which is used for the server application, historical data, and backup storage. Users can also manually back up or restore the SmartStruxure server device to a storage location on a PC or network. Through the Enterprise Server, users have the ability to perform scheduled backups of associated SmartStruxure server device to network storage for even greater levels of protection.

IT friendly

AS-B communicates using the networking standards. This makes installations easy, management simple, and transactions secure.

TLS support

Communication between clients and the SmartStruxure servers can be encrypted using Transport Layer Security (TLS 1.0). The servers are delivered with a default self-signed certificate. Commercial Certification Authority (CA) server certificates are supported to lower the risk of malicious information technology attacks. Use of encrypted communication can be enforced for both WorkStation and WebStation access.

Supported protocols
  • IP addressing

  • TCP communications

  • DHCP for easy network configuration

  • DNS for simple lookup of addresses

  • HTTP/HTTPS for Internet access through firewalls, which enables remote monitoring and control

  • NTP (Network Time Protocol) for time synchronization throughout the system

  • SMTP or SMTPS with support for SSL/TLS based authentication, enables sending email messages triggered by schedule or alarm

  • SNMP enables network supervision and reception of application alarms in designated network management tools

Simple DIN-rail installation

Fasteners easily snap into a locked position for panel installation. The fastener has a quick-release feature for easy DIN-rail removal.

Removable terminal blocks

AS-B uses plugable terminal blocks, which are easy to install and remove from the device. The terminal blocks are ordered separately from Schneider Electric.

Efficient terminal management

The input and output terminals are clearly labeled. The Building Operation WorkStation software can generate custom as-built labels for AS-B.


Protection components on the universal inputs/outputs, digital inputs, and triac outputs protect against high-voltage short-duration transient events. Universal inputs/outputs configured as current inputs (Ub only) are protected against over current. Universal inputs/outputs configured as voltage outputs have current limits to protect against permanent short-circuit to ground.

AC input
Nominal voltage
24 VAC
Operating voltage range
+/- 20 %
50/60 Hz
Maximum current
0.5 A rms
Recommended transformer rating
≥15 VA
DC input
Nominal voltage
24 to 30 VDC
Operating voltage range
21 to 33 VDC
Maximum power consumption
10 W
Ambient temperature, operating
0 to 50 °C (32 to 122 °F)
Ambient temperature, storage
-20 to +70 °C (-4 to +158 °F)
Maximum humidity
95 % RH non-condensing
Plastic flame rating
Ingress protection rating
IP 20
198 W x 110 H x 64 D mm (7.8 W x 4.3 H x 2.5 D in.)
Weight, including terminal blocks
0.504 kg (1.111 lb) a
Weight, excluding terminal blocks
0.420 kg (0.926 lb) a
Agency compliances
RCM; BS/EN 61000-6-3; BS/EN 50491-5-2; FCC Part 15, Sub-part B, Class B
BS/EN 61000-6-2; BS/EN 50491-5-3
Safety standards
BS/EN 60730-1; BS/EN 60730-2-11; BS/EN 50491-3; UL 916 C-UL US Listed
BS/EN 50491-1
Real-time clock
Accuracy in runtime mode
NTP server
Accuracy in backup mode, at 25 °C (77 °F)
+/-52 seconds per month
Backup time, at 25 °C (77 °F)
10 days
Communication ports
Dual 10/100BASE-TX (RJ45)
USB 2.0, 5 VDC, 2.5 W, 1 device port (mini-B) and 1 host port (type-A)
2-wire port, bias 5.0 VDC
BACnet/IP and MS/TP, port configurable, default 47808
Modbus TCP, client and server
Serial, RS-485, client and server
Binary, port fixed, 4444
Non-binary, port configurable, default 80
Encrypted supporting TLS 1.0, port configurable default 443
Email sending, port configurable, default 25
Email sending, port configurable, default 587
version 3
Network supervision using poll and trap
Application alarm distribution using trap
333 MHz
SPEAr320S, ARM926 core
256 MB
eMMC memory
4 GB
Memory backup
Yes, battery-free, no maintenance
Display resolution
128 x 64 pixels
Display size
36 W x 17 H mm (1.4 W x 0.7 H in.)
Display type
FSTN monochrome LCD, white color transflective backlight
Part numbers
SmartX Controller – AS-B-24
SmartX Controller – AS-B-24H
Includes display
SmartX Controller – AS-B-36
SmartX Controller – AS-B-36H
Includes display
AS-B connector kit (includes terminal blocks)
AS-B installer kit
Add-on options
SW-EWS-1, EcoStruxure Web Services (run-time) option
Consume only for one SmartStruxure server
SW-EWS-2, EcoStruxure Web Services (run-time) option
Serve & Consume for one SmartStruxure server
SW-EWS-3, EcoStruxure Web Services (run-time) option
Serve & Consume, plus Historical trend log data for one SmartStruxure server
SW-GWS-1, Web Services (Generic Consume) option
For one SmartStruxure server
SW-SNMP-1, Alarm notifications via SNMP option
For one SmartStruxure server
SW-SMART-CONNECT, Smart Connector deployment license
For one Smart Connector deployment
Universal inputs/outputs, Ua and Ub
Channels, AS-B with 24 I/O points
12 Ua, Ua1 to Ua12
4 Ub, Ub1 to Ub4
Channels, AS-B with 36 I/O points
20 Ua, Ua1 to Ua20,
8 Ub, Ub1 to Ub8
Absolute maximum ratings
-0.5 to +24 VDC
A/D converter resolution
16 bits
Digital inputs
Dry contact switch closure or open collector/open drain, 24 VDC, typical wetting current 2.4 mA
Minimum pulse width
120 ms
Counter inputs
Dry contact switch closure or open collector/open drain, 24 VDC, typical wetting current 2.4 mA
Minimum pulse width
20 ms
Maximum frequency
25 Hz
Supervised inputs
5 V circuit, 1 or 2 resistors
Monitored switch combinations
Series only, parallel only, and series and parallel
Resistor range
1 to 10 kohm
For a 2-resistor configuration, each resistor must have the same value +/- 5 %
Voltage inputs
0 to 10 VDC
+/-(7 mV + 0.2 % of reading)
0.5 mV
100 kohm
Current inputs
0 to 20 mA
+/-(0.01 mA + 0.4 % of reading)
1 μA
47 ohm
Resistive inputs
10 ohm to 10 kohm accuracy
+/-(7 + 4 x 10 -3 x R) ohm
R = Resistance in ohm
10 kohm to 60 kohm accuracy
+/-(4 x 10 -3 x R + 7 x 10 -8 x R 2 ) ohm
R = Resistance in ohm
Temperature inputs (thermistors)
-50 to +150 °C (-58 to +302 °F)
Supported thermistors
20 kohm
Type I (Continuum)
10 kohm
Type II (I/NET)
10 kohm
Type III (Satchwell)
10 kohm
Type IV (FD)
10 kohm
Type V (FD w/ 11k shunt)
Linearized 10 kohm
Satchwell D?T
Linearized 10 kohm
Johnson Controls
2.2 kohm
1.8 kohm
1 kohm
Measurement accuracy
20 kohm
-50 to -30 °C: +/-1.5 °C (-58 to -22 °F: +/-2.7 °F)
-30 to 0 °C: +/-0.5 °C (-22 to +32 °F: +/-0.9 °F)
0 to 100 °C: +/-0.2 °C (32 to 212 °F: +/-0.4 °F)
100 to 150 °C: +/-0.5 °C (212 to 302 °F: +/-0.9 °F)
10 kohm, 2.2 kohm, and 1.8 kohm
-50 to -30 °C: +/-0.75 °C (-58 to -22 °F: +/-1.35 °F)
-30 to +100 °C: +/-0.2 °C (-22 to +212 °F: +/-0.4 °F)
100 to 150 °C: +/-0.5 °C (212 to 302 °F: +/-0.9 °F)
Linearized 10 kohm
-50 to -30 °C: +/-2.0 °C (-58 to -22 °F: +/-3.6 °F)
-30 to 0 °C: +/-0.75 °C (-22 to +32 °F: +/-1.35 °F)
0 to 100 °C: +/-0.2 °C (32 to 212 °F: +/-0.4 °F)
100 to 150 °C: +/-0.5 °C (212 to 302 °F: +/-0.9 °F)
1 kohm
-50 to +150 °C: +/-1.0 °C (-58 to +302° F: +/-1.8 °F)
RTD temperature
Supported RTDs
Pt1000, Ni1000, and LG-Ni1000
-50 to +150 °C (-58 to +302 °F)
Measurement accuracy
-50 to +70 °C: +/-0.5 °C (-58 to +158 °F: +/-0.9 °F)
70 to 150 °C: +/-0.7 °C (158 to 302 °F: +/-1.3 °F)
-50 to +150 °C (-58 to +302 °F)
Measurement accuracy
+/-0.5 °C (+/-0.9 °F)
-50 to +150 °C (-58 to +302 °F)
Measurement accuracy
+/-0.5 °C (+/-0.9 °F)
RTD temperature wiring
Maximum wire resistance
20 ohm/wire (40 ohm total)
Maximum wire capacitance
60 nF
The wire resistance and capacitance typically corresponds to a 200 m wire.
RTD resistive
1,000 ohm
500 to 2,200 ohm
Including wiring resistance
Measurement accuracy
+/-(0.2 + 1.5 x 10 -3 x R) ohm
R = resistance in ohm
0.1 ohm
RTD resistive wiring
Maximum wire capacitance
60 nF
Voltage outputs
0 to 10 VDC
+/-60 mV
10 mV
Minimum load resistance
5 kohm
Load range
-1 to +2 mA
Digital inputs, DI
Channels, AS-B with 24 I/O points
4, DI1 to DI4
Channels, AS-B with 36 I/O points
Absolute maximum ratings
-0.5 to +24 VDC
Digital inputs
Dry contact switch closure or open collector/open drain, 24 VDC, typical wetting current 2.4 mA
Minimum pulse width
120 ms
Counter inputs
Dry contact switch closure or open collector/open drain, 24 VDC, typical wetting current 2.4 mA
Minimum pulse width
20 ms
Maximum frequency
25 Hz
Relay outputs, DO
Channels, AS-B with 24 I/O points
4, DO1 to DO4
Channels, AS-B with 36 I/O points
4, DO1 to DO4
Contact rating
250 VAC/30 VDC, 2 A, Pilot Duty (C300)
Switch type
Form A Relay
Single Pole Single Throw
Normally Open
Isolation contact to system ground
3000 VAC
Cycle life (Resistive load)
At least 100,000 cycles
Minimum pulse width
100 ms
Triac outputs, DO
Channels, AS-B with 24 I/O points
Channels, AS-B with 36 I/O points
4, DO5 to DO8
Output rating
Max. 0.8 A
24 VAC +/-20 %
COM1 for DO5 and DO6
COM2 for DO7 and DO8
The common terminals COM1 and COM2 can be connected to 24 VAC or to ground.
Common voltage, high side output
24 VAC
Common voltage, low side output
0 VAC (ground)
Minimum pulse width
100 ms


AS-B model with 24 I/O points

AS-B model with 24 I/O points

AS-B model with 36 I/O points

AS-B model with 36 I/O points

For protection from excess current that could be produced by field wiring, follow these instructions:

  • Connect RET terminal number 4 or 5 to a common chassis/signal ground rail in the control panel using a size 2.5 mm² (13 AWG) or larger wire. The wire must have a current rating greater than or equal to 16 A.

  • AS-Bs with 24 I/O points have more RET terminals for connection of I/O returns, so the common chassis/signal ground rail is optional and may not be needed.

  • Individual 24 VDC power sources to the field must be current limited to maximum 4 A for UL compliant installations, and maximum 6 A in other areas.

For more information on wiring, see Hardware Reference Guide.

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