SIEMENS 6ES5955-3LC14
- EICHLER-art.no.: K0136528
Product description
SIMATIC S5 955 POWER SUPPLY UNIT F. CC 135U/EU 183U/EU 185U 115/230V AC; 5V DC, 18A
Services for SIEMENS 6ES5955-3LC14
SIEMENS |
6ES5955-3LC14 –
additional product information
| Delivery information | |||
|---|---|---|---|
| Export identifier | AL: ECCN: | ||
| Net weight | 4.438 | ||
| Quantity | 1 Stück | ||
| Packaging quantity | 1 | ||
| Additional product information | |||
|---|---|---|---|
| Product status | EOP: 1995-07-01 | ||
| EAN | / | ||
| UPC | / | ||
| Static lot number | 85044090 | ||
| List indicator | / | ||
| Product group | 4309 | ||
| Country of origin | AT | ||
| Compliance with the substance restrictions according to RoHS directive | Since: / | ||
| Product classifications | Version | Classification | |
|---|---|---|---|
| eClass | 4 | / | |
| eClass | 5.1 | / | |
| eClass | 6.0 | / | |
| ETIM | 3 | / | |
| ETIM | 4 | / | |
| ETIM | 5 | / | |
What is 6ES5955-3LC14 and where is it used?
The 6ES5955-3LC14 is a Siemens SIMATIC S5 PS 955 power supply designed for S5-135U/S5-155U central racks as well as 183U/185U expansion units. Its purpose is to provide the stable logic voltage required by the CPU, memory and peripheral modules.
In existing installations, this power supply is typically found in older S5 systems that remain in productive operation. A failure can immediately result in production downtime, I/O faults or CPU stop conditions. For maintenance teams and purchasing departments, the article number is therefore particularly important when identifying a faulty power supply, sourcing a compatible replacement or organising a repair with minimal downtime.
Overview of the key technical data and what it means
The 6ES5955-3LC14 is designed for 115/230 V AC input voltage and provides a 5 V DC output with a rated current of 18 A.
The 18 A output rating is particularly important because it determines the maximum rack and module load that can be supplied. Siemens also specifies two integrated cooling fans with airflow monitoring via PTC sensors. If a fan fails, the condition is indicated through an LED and a relay output. Depending on the jumper configuration, the power supply can automatically shut down in response to a fan fault.
For proper operation, Siemens specifies a minimum load of 1 A on the 5 V output for 18 A power supply variants. Other important features include:
- Selectable 115/230 V AC input voltage
- Battery monitoring functions
- Fan monitoring functions
- Diagnostic signalling via relay contacts
- Configurable shutdown behaviour through jumper settings
For maintenance personnel, these features are particularly relevant when troubleshooting unexplained rack shutdowns or intermittent power-related faults.
Product status, life-cycle status and obsolescence
The EICHLER product information lists an EOP (End of Production) date of 01 July 1995 for the 6ES5955-3LC14.
For operators, this clearly places the power supply in the category of obsolescence and lifecycle management. As a result, spare-parts availability, repair capability, inventory planning and documented functional testing become significantly more important than standard new-product procurement.
In S5 environments, risks are increasingly associated with:
- Ageing cooling fans
- Ageing backup batteries
- Connector and contact degradation
- Limited manufacturer support and availability
No clearly documented direct Siemens successor specifically for 6ES5955-3LC14 could be verified from the available Siemens sources. Consequently, replacement decisions should not be based solely on matching current ratings. The correct rack type, electrical integration, hardware version and jumper configuration must also be verified.
EICHLER services and when they are relevant in practice
For operators of legacy S5 systems, EICHLER services become particularly valuable when production downtime, limited spare-parts availability or obsolescence risks require immediate action.
For the 6ES5955-3LC14, EICHLER offers:
- Repair
- Exchange
- Refurbished units
- New units on request
The repair service is specified with a turnaround time of 2–5 days and includes:
- Technical cleaning
- Preventive maintenance
- Comprehensive functional testing
- Minimum 24-month warranty
An optional test report for power supplies is also available.
In practice, these services are especially valuable when original hardware must remain in operation within an existing S5 environment and when predictable recommissioning, documented functionality and system continuity are more important than a complete control-system migration.
| Fault description | Possible solution |
|---|---|
| Why does the “Fan Fault” LED light up on a 6ES5955-3LC14 and the power supply shuts down after a few seconds? | Siemens monitors airflow using PTC sensors. If a fan fails or airflow becomes insufficient, the fault is indicated via the LED and relay output. When the F-R jumper is closed, the power supply automatically switches off after approximately 6 to 10 seconds. Check the fans, connectors, air filters and airflow path. Repair or replace the fan assembly and ensure that the system is powered down within 60 seconds if the F-R jumper has been opened temporarily for diagnostic purposes. |
| Why does the 6ES5955-3LC14 display “Voltage Low”? | This LED indicates an undervoltage condition at the load-voltage monitoring input. Check the external 24 V monitoring circuit, the BA-EX jumper setting, and whether the incoming supply voltage reaches its nominal value quickly enough. Also measure the 5 V output voltage under load, as Siemens specifies a minimum load of 1 A on the 5 V output for 18 A power supplies to ensure correct operation. |
| Why does the “Batt. Low” LED illuminate and why are buffered data lost after a power cycle? | According to Siemens, this indicates that the battery voltage has fallen below the specified threshold. The backup battery can be replaced while the power supply is energised or by using an external 3.4 V support supply. After replacement, check the battery monitoring function, perform the required reset acknowledgement and verify CPU startup behaviour. Preventive battery replacement at regular maintenance intervals is strongly recommended, as Siemens specifies periodic battery replacement for reliable data retention. |
| Why does the power supply fail to start correctly or why is the 5 V output unstable? | First verify that the correct 115/230 V input voltage setting has been selected and that the protective earth connection is properly connected. Siemens specifies that the supply voltage must reach its nominal value within a maximum of 200 ms. In addition, 18 A power supplies require a minimum load of 1 A on the +5 V output. If the behaviour remains abnormal, measure the output voltage under a defined load condition and consider a comprehensive functional test or repair. |
| Why does a replacement power supply provide incorrect voltages or not work immediately after installation? | On later 18 A S5 power supplies, jumper settings and device configuration are critical. Siemens documents jumper configurations for successor models, and practical service cases have shown situations where incorrect settings resulted in 15 V being measured instead of 5 V after replacement. Before installation, always verify the part number, rack type, jumper configuration and monitoring functions rather than selecting a replacement solely based on the 18 A current rating. |
Is 6ES5955-3LC14 still part of the regular Siemens life cycle?
No. The 6ES5955-3LC14 has an EOP (End of Product) status dated 01 July 1995. For purchasing departments, this means that the module should no longer be regarded as a standard production product but rather as an obsolete spare part. As a result, reliable testing procedures, repair options, exchange stock and documented functional reliability are generally more important than expecting normal new-product availability.
Which SIMATIC S5 systems is the 6ES5955-3LC14 intended for?
The power supply is designed for S5-135U/-155U central systems as well as 183U/185U expansion units. This makes it a typical power supply for older modular SIMATIC S5 rack configurations. In practice, this allocation is important because, in S5 legacy systems, suitability depends not only on the part number but also on the specific rack type and application environment.
Is there an officially designated Siemens successor for the 6ES5955-3LC14?
No explicitly designated direct successor for the 6ES5955-3LC14 was identified in the reviewed Siemens sources. Siemens does provide compatibility and jumper information for later 3xx41/3xx42 power supply variants; however, replacement decisions for this exact MLFB should always be verified technically. For operators, matching the actual system configuration is therefore more important than selecting a seemingly similar unit solely on the basis of its current rating.
When is repair more economical than replacement?
Repair is particularly attractive when the existing S5 hardware is intended to remain in service, downtime must be minimised and a tested original unit is preferred. The EICHLER product information specifies a repair turnaround time of 2–5 days. In addition, the repair service includes cleaning, preventive maintenance, functional testing and a minimum 24-month warranty. This approach is especially valuable for operators wishing to avoid retrofit risks and maintain the stability of the existing system configuration.
What should purchasing departments pay particular attention to when sourcing a 6ES5955-3LC14?
The most important factors are the exact part number, the intended rack type, the condition of the unit and the scope of testing performed. With obsolete S5 power supplies, documented functionality, warranty coverage, diagnostic capability and a clearly defined service option are often more important than simply finding a matching part number. It is also advisable to determine in advance whether repair, exchange, used stock or new stock on request represents the most suitable supply strategy.
What should be checked before reinstallation or commissioning?
Before reinstallation, the input voltage selector, the 5 V output under load, fan operation, battery condition and jumper configuration should all be verified. Siemens specifies a minimum load of 1 A on the +5 V output for 18 A power supplies and states that the supply must reach its nominal voltage within 200 ms. In addition, the power supply must not be inserted or removed while the system is energised. Checking these points in advance significantly reduces the risk of startup failures, thermal issues and difficult-to-diagnose S5 system faults.
