6ES5451-4UA13 SIMATIC S5 451
The Siemens SIMATIC S5 451 (part number 6ES5451-4UA13) is a digital output module belonging to the classic SIMATIC S5 programmable logic controller family. It is designed to interface with S5-series CPUs such as the S5-115U, S5-135U, and S5-155U, providing discrete output signals to field devices. This module was manufactured by Siemens as part of the well-established S5 automation platform, which was widely deployed across industrial sectors from the 1980s through the 2000s.
The 6ES5451-4UA13 provides 32 digital outputs with a 24 V DC signal level, organized in groups with common potential. Outputs are transistor-based, offering fast switching response suitable for time-critical control tasks. The module slots into the S5 subrack and communicates with the CPU via the S5 backplane bus. It includes LED status indicators for each output channel, enabling rapid visual diagnostics during commissioning and fault-finding. The module supports short-circuit and overload protection on its output channels.
The SIMATIC S5 451 output module is used extensively in manufacturing automation, process control, and machine tool applications where a large number of discrete output signals are required. It is commonly found in automotive assembly lines, packaging machinery, conveyor systems, and chemical processing plants. Despite the S5 platform being a legacy system, many installations remain in service, making refurbished and tested modules such as the 6ES5451-4UA13 critical for maintaining operational continuity.
Technical Specifications
| Output Type | Digital (Discrete) Outputs |
|---|---|
| Number of Outputs | 32 |
| Output Voltage | 24 V DC |
| Output Current per Channel | 0.5 A |
| Total Output Current | 4 A (per group) |
| Signal Level (High) | 24 V DC |
| Output Technology | Transistor (sourcing) |
| Short-Circuit Protection | Yes |
| Status Indicators | LED per output channel |
| Bus Interface | SIMATIC S5 backplane bus |
| Operating Temperature | 0 °C to +60 °C |
| Storage Temperature | -40 °C to +70 °C |
| Relative Humidity | 5% to 95% (non-condensing) |
| Mounting | S5 subrack (rail-mounted module) |
| Series/Product Family | SIMATIC S5 |
Common Diagnostic Codes
- SF (Group Error LED)
- Group fault indicator on the module is lit, indicating one or more output channels have a fault condition such as short-circuit or overload.
Identify the affected channel using individual channel LEDs. Remove the load, check wiring for short-circuits, and restore power. Replace the module if the fault persists. - Output LED Off (No Signal)
- An output channel LED is off despite the CPU commanding the output ON, indicating a possible blown internal output driver or wiring fault.
Verify the CPU output command using the programming device. Check wiring continuity to the field device. Replace the module if the driver is confirmed faulty. - Bus Error (CPU Diagnostic)
- The CPU reports a module access error or slot fault, indicating the S5 451 module is not responding correctly on the backplane bus.
Reseat the module firmly in the subrack slot. Check backplane bus connectors for damage or contamination. Swap the module to a known-good slot to isolate the fault. - Overload / Short-Circuit (Channel)
- An output channel has detected an overload or short-circuit condition, causing the output driver to shut down to protect the module.
Disconnect the load from the affected channel. Measure the load impedance and verify it is within specification. Reconnect after resolving the short-circuit or overload condition. - Module Not Recognized (CPU OB Error)
- The CPU triggers an organization block error (OB 85 or OB 86) indicating the output module is missing or not accessible at the configured address.
Confirm the module is correctly seated in the subrack. Verify the hardware configuration in STEP 5 matches the physical slot assignment. Check subrack power supply voltage. - Supply Voltage Fault (L+ Missing)
- The 24 V DC load supply voltage to the module output stage is absent, causing all outputs to remain de-energized regardless of CPU commands.
Measure the 24 V DC supply at the module front connector terminals. Check the external power supply and fusing. Restore the supply voltage to the correct level.
Frequently Asked Questions
How many digital outputs does the 6ES5451-4UA13 provide?
The 6ES5451-4UA13 provides 32 digital outputs at 24 V DC, organized in groups with a common supply connection.
Which SIMATIC S5 CPUs are compatible with this output module?
The module is compatible with S5-series CPUs including the S5-115U, S5-135U, and S5-155U when installed in the appropriate S5 subrack.
What programming software is used to configure the 6ES5451-4UA13?
The module is configured and programmed using Siemens STEP 5 software, which is the standard programming environment for the SIMATIC S5 platform.
Is the 6ES5451-4UA13 still in production?
No, the SIMATIC S5 product family has been discontinued by Siemens. Refurbished and tested units are the primary source for replacement modules in existing installations.
What is the maximum output current per channel on this module?
Each output channel is rated for a maximum of 0.5 A, with the total current per output group not exceeding 4 A.
Troubleshooting
All outputs remain de-energized despite correct CPU program execution
Check the 24 V DC load supply voltage at the module front connector. Verify the module is correctly addressed in the STEP 5 hardware configuration and seated firmly in the subrack.
Restore the 24 V DC external supply if absent. Reseat the module and confirm the slot address matches the STEP 5 configuration. Use the STEP 5 status monitoring function to verify output commands from the CPU.
Individual output channel does not switch despite CPU command
Use STEP 5 online monitoring to confirm the CPU is commanding the output bit. Measure the output terminal voltage with a multimeter. Check the connected load for a short-circuit or open circuit.
If the CPU command is confirmed but no output voltage is present, the output transistor driver for that channel may be faulty. Replace the module with a tested unit.
CPU reports OB 85 or OB 86 organization block call related to this module
The CPU cannot access the module at the configured address. Check that the module is physically present in the correct subrack slot and that the backplane bus connectors are clean and undamaged.
Reseat the module firmly. Clean backplane bus contacts if corroded. Verify the STEP 5 hardware configuration matches the physical installation. Replace the module if the error persists after reseating.
Module runs hot or output channels shut down intermittently
Measure the total load current drawn by all active outputs simultaneously. Compare against the module's rated group current limit. Check subrack ventilation and ambient temperature.
Reduce the simultaneous load current by redistributing outputs across multiple modules if the group current limit is exceeded. Ensure adequate subrack ventilation and that ambient temperature is within the 0 to 60 °C operating range.
LED status indicators on the module front panel are all off with power applied
Check the subrack power supply output voltage. Inspect the module for visible damage such as burnt components. Verify the backplane bus is supplying the correct internal voltages to the module.
Confirm the subrack power supply is functioning correctly and delivering the required voltages. If the supply is healthy and the module shows no signs of life, the module's internal power regulation circuitry may have failed and the module should be replaced.
| Condition | Repair, Used, Refurbished, New in box (sealed) |
|---|
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