Product Overview

The Schneider Electric SR2A101FU is a Zelio Logic compact smart relay for small-scale industrial automation and electrical control applications. It operates on a 100–240 V AC supply and combines six AC digital inputs, four relay outputs, programmable logic, and an integrated LCD display in one control device. With ten onboard I/O points, it is suited to machines and utility systems that need straightforward sequencing without a larger PLC installation.

The SR2A101FU differs from the SR2A101BD primarily in its power supply and input characteristics. The FU version uses an AC supply and accepts compatible AC signals at its digital inputs, whereas the BD version operates from 24 V DC and uses 24 V DC input signals. This distinction is important when selecting a smart relay for an existing control panel, particularly where the field devices and available control voltage are already established.

The six inputs can receive signals from compatible AC-operated switches and other discrete control devices. The four relay outputs switch external circuits according to the programmed logic. Within their electrical ratings, these outputs can operate contactor coils, indicator circuits, interface relays, and other control loads.

For example, a small ventilation system may use the SR2A101FU to process operator commands and equipment status signals, then control a fan contactor through a relay output. The program can coordinate start and stop conditions and implement simple interlocks. The fan motor itself remains connected through an appropriately rated power circuit and protective arrangement.

The integrated LCD and navigation buttons provide a local interface for monitoring and working with the controller. Programs can be developed using Zelio Soft, with ladder logic and function block diagram programming available for supported applications. Ladder logic is particularly familiar to technicians accustomed to conventional relay circuits, while function block diagrams can help organize more complex control relationships.

The smart relay’s EEPROM memory retains the stored program for up to ten years at the specified reference temperature of 25°C. This helps preserve the control program during power interruptions. The model does not include a real-time clock, however, so applications requiring built-in calendar-based scheduling need a different controller or an appropriate external timing arrangement.

The SR2A101FU is suitable for relatively simple control sequences based on discrete inputs and relay outputs. Applications involving analog measurements, high-speed motion control, extensive network communication, or large numbers of I/O points require a broader assessment of the controller architecture.

Relay-output selection also deserves attention. The connected load’s voltage, current, inrush characteristics, and switching frequency affect contact performance and service life. Where a load exceeds the output’s permitted ratings, a suitably rated interface relay or contactor should be used rather than switching it directly.

The Schneider SR2A101FU is therefore a practical option for standalone automation tasks where AC-powered control, an integrated display, and programmable relay outputs are required in a compact controller.

Technical Specifications

Product Features

• 100–240 V AC supply: Fits control panels using an AC-powered smart relay.
• Six AC digital inputs: Accepts compatible discrete signals within the specified input voltage range.
• Four relay outputs: Switches suitable external AC or DC control circuits.
• Integrated LCD display: Supports local monitoring and navigation.
• Ladder logic and FBD programming: Provides two programming approaches for implementing control sequences.
• EEPROM program retention: Preserves stored program data for up to ten years at 25°C.
• No real-time clock: Suits applications that do not depend on built-in calendar scheduling.
• DIN rail or screw mounting: Supports installation in compatible electrical enclosures.
• Standalone logic control: Combines signal processing and relay switching in one unit.
• Zelio Soft programming support: Allows technicians to develop and maintain compatible control programs.

Working Principle

The SR2A101FU reads the states of its six AC digital inputs, evaluates the user-defined program, and controls its four relay outputs according to the programmed conditions.

100–240 V AC Supply → SR2A101FU → Program Execution → Relay Outputs → External Control Loads

The input circuits receive signals from compatible AC field devices. A switch may indicate an operating request, while an auxiliary contact can report the status of external equipment. The controller reads these signals and makes their states available to the application program.

The program evaluates the input conditions and determines whether each output should be activated. For example, a fan-control program may require a start command and a valid interlock before energizing an output. A separate stop condition can interrupt the sequence, while additional logic can coordinate alarms or operating states.

Ladder logic represents these conditions using contacts, coils, and supported logic functions. Function block diagram programming uses interconnected functional blocks to express the same type of control relationships. The choice depends on the program structure and the user’s preferred development method.

When an output is commanded on, its relay contacts change state and switch the connected control circuit. The output may energize a contactor coil, which then switches the motor’s power circuit. The smart relay’s contacts must remain within their specified voltage and current ratings, and they should not replace dedicated motor switching or protection equipment.

The integrated LCD provides local access to supported display and navigation functions. During commissioning, the programming software can be used to create the application and transfer it to the controller. The input and output states should then be tested against the actual field wiring and the intended machine sequence.

Because the SR2A101FU accepts 100–240 V AC digital input signals, its input wiring must be treated differently from that of a 24 V DC smart relay. The field-device voltage and the controller’s input requirements must match. Mixing incompatible voltage levels or wiring arrangements can prevent correct signal detection or damage equipment.

The four relay outputs support compatible AC or DC loads, but load selection must consider contact voltage, current, inrush, and switching frequency. Inductive loads can generate transients when switched, so suitable suppression may be required. Higher-current loads should be operated through properly rated external switching equipment.

The EEPROM memory retains the stored program for up to ten years at 25°C. This protects the program against loss of supply, but it does not replace the need to document the application and maintain a verified backup copy. The controller’s behavior after power restoration must also be considered as part of the machine’s operating sequence.

The absence of a real-time clock means that built-in calendar-based scheduling is not available. The controller can still execute logic based on its inputs and supported internal functions, but time-of-day or day-of-week operations require another solution.

If an output does not operate, the investigation should distinguish between an unmet program condition, an incorrect output assignment, a supply problem, and a fault in the external load circuit. Checking the input states, program logic, relay output state, and connected equipment in sequence helps isolate the cause.

Through AC input monitoring, programmable logic, and relay-based switching, the SR2A101FU provides a straightforward control solution for compatible small automation systems.

Role in the Industrial Control Architecture

The SR2A101FU acts as a local programmable controller between AC field signals and external control loads. It evaluates input conditions and switches its relay outputs according to the stored program.

AC Field Signals → SR2A101FU → Relay Outputs → Contactors and Control Loads

The SR2A101FU handles basic programmed control. Motor power switching, electrical protection, and safety-related functions must be implemented using appropriately selected external equipment and circuit arrangements.

Industrial Applications

Installation and Maintenance

1. Verify the model reference: Confirm that the installed unit is SR2A101FU and that AC-powered inputs match the application requirements.
2. Prepare the control enclosure: Provide suitable mounting, wiring access, and environmental conditions for the IP20 device.
3. Install the smart relay: Use a compatible 35 mm DIN rail or the supported screw-fixing arrangement.
4. Check the AC supply: Verify the supply voltage and frequency against the specified operating range.
5. Identify the input circuits: Label each field signal and verify that its voltage is compatible with the 100–240 V AC inputs.
6. Wire the relay outputs: Follow the terminal diagram and keep each connected load within the applicable contact ratings.
7. Review switching loads: Check voltage, current, inrush, and inductive characteristics before connecting contactor coils or other loads.
8. Develop the control program: Implement the required logic using supported ladder or function block diagram programming.
9. Test operating sequences: Verify start conditions, stop commands, interlocks, and output responses under controlled conditions.
10. Check power-restoration behavior: Confirm that equipment returns to operation in the intended manner after an interruption of supply.
11. Inspect external control circuits: Check contactors, interface relays, protective devices, terminal tightness, and field wiring.
12. Maintain program records: Keep the approved program, I/O assignments, wiring diagrams, and commissioning details for future servicing.

If the controller does not detect an input, check the field signal voltage, wiring, and terminal connection. If an output fails to operate, inspect the program condition, output state, external supply, and connected load. Isolate the electrical supply before performing wiring or maintenance work.

Related Components

Recommended Related Models

Key Advantages

• Combines six AC digital inputs, four relay outputs, and programmable logic in one device.
• Operates from a 100–240 V AC supply.
• Provides an integrated LCD display for local interaction.
• Supports ladder logic and function block diagram programming.
• Retains stored program data for up to ten years at 25°C.
• Supports DIN rail or screw mounting in suitable control enclosures.
• Suits small automation tasks that do not require a larger PLC system.

Technical FAQs

How does the SR2A101FU differ from the SR2A101BD?

The SR2A101FU operates from a 100–240 V AC supply and accepts compatible 100–240 V AC digital input signals. The SR2A101BD uses a 24 V DC supply and 24 V DC inputs. The correct model depends on the available control supply and the voltage of the field signals.

Can the SR2A101FU provide calendar-based scheduling?

No. This model does not include a real-time clock. It can execute programmed logic based on its inputs and supported internal functions, but calendar-based scheduling requires a different smart relay with clock functionality or a suitable external timing arrangement.

What should be considered when connecting contactor coils to the relay outputs?

Check the coil voltage, steady-state current, inrush characteristics, and the output contact ratings. Inductive loads can generate switching transients, so suitable suppression may be necessary. A properly rated interface relay or contactor should be used where the load exceeds the smart relay’s direct switching capability.

How is the stored program protected during a power interruption?

The controller uses EEPROM memory to retain program data for up to ten years at 25°C. This helps preserve the application when supply power is lost. A separate verified program backup and a safe power-restoration sequence remain important for maintenance and machine operation.