Siemens 6ES5926-3KA12 Upgrade Solution for SIMATIC S5

Product Overview

Siemens 6ES5926-3KA12 Upgrade Solution for SIMATIC S5: Smooth Transition from Legacy to Modern Control

The Siemens 6ES5926-3KA12 is the CPU926 central processing unit designed for the SIMATIC S5-115U programmable logic controller platform — one of Siemens’ most widely deployed industrial automation systems across global manufacturing, utilities, and process industries. Although the S5 series has reached end-of-life status, tens of thousands of installations worldwide continue to rely on this architecture for continuous production. TOPNLMS maintains verified stock of the 6ES5926-3KA12 to support both direct spare-part replacement and structured migration projects, ensuring your facility can maintain uptime while planning a controlled transition to modern platforms.

Whether you are sourcing an emergency replacement to restore a tripped production line or executing a phased upgrade from SIMATIC S5 to SIMATIC S7-300 or SIMATIC S7-400, the 6ES5926-3KA12 serves as the critical anchor point of your migration strategy. Its compatibility with the S5-115U rack, existing I/O wiring, and STEP 5 programming environment means that a direct swap can be completed with minimal re-engineering, dramatically reducing planned and unplanned downtime.

Compatibility Comparison Table

Seamless Upgrade Solutions

A successful migration away from the SIMATIC S5-115U platform — or a reliable direct replacement of the 6ES5926-3KA12 — depends on the coordinated availability of several interconnected components. When the CPU926 is replaced in-kind, the existing 6ES5926-3KA12 slots directly into the S5-115U central controller rack alongside the installed digital and analog I/O modules, such as the 6ES5430-4UA12 digital input module and 6ES5470-4UA12 analog input module, without requiring any wiring changes. The power supply module — typically a 6ES5955-3LC41 or equivalent S5 PS unit — continues to feed the rack at 24 VDC, maintaining the existing cabinet layout and minimizing re-commissioning effort.

For facilities planning a structured migration to the S7 platform, the process typically begins with installing a SIMATIC S7-300 CPU315-2 DP on a new DIN rail section within the same control cabinet, running in parallel with the S5 system during the transition period. Communication between legacy field devices and the new controller is bridged using a CP343-1 Industrial Ethernet communication processor or a CP342-5 PROFIBUS DP module, enabling the new S7 CPU to take over field bus communication while the S5 system remains operational. Signal wiring from existing field instruments is re-terminated to SM321 digital input modules and SM331 analog input modules on the S7 rack using standard terminal adapter sets, preserving the original cable runs.

HMI panels connected to the S5 system via point-to-point serial links — such as older OP7 or OP17 operator panels — can be retained during the transition or replaced with modern KTP700 Basic or KTP900 Basic panels communicating over PROFINET, depending on the project scope. Programming and configuration of the new S7 platform is performed using STEP 7 v5.6 or TIA Portal V17/V18, with the S5-to-S7 program conversion tool (S5-S7 Converter) assisting in translating existing STEP 5 ladder logic and function block diagrams. Throughout the migration, the 6ES5926-3KA12 remains the operational backbone of the S5 system, ensuring zero production interruption until the cutover is complete and validated.

Retrofit Guidance FAQ

Q1: Can the 6ES5926-3KA12 be installed as a direct replacement without modifying existing wiring or I/O modules?
Yes. The 6ES5926-3KA12 CPU926 is a direct slot-compatible replacement for the S5-115U central controller rack. All existing digital and analog I/O modules, power supply connections, and field wiring remain unchanged. The replacement CPU retains the same physical form factor and bus interface as the original unit. After installation, the existing STEP 5 program stored on the memory module (EPROM/EEPROM) is loaded automatically, and the system resumes normal operation following a cold restart. No rewiring or I/O reconfiguration is required for a like-for-like replacement.

Q2: What communication protocols does the 6ES5926-3KA12 support, and how does this affect migration planning?
The CPU926 natively supports SINEC H1 (Industrial Ethernet via CP1430 TF) and point-to-point serial communication (TTY 20 mA current loop and RS-232C) through dedicated communication processors installed in the S5 rack. It does not natively support PROFIBUS DP or PROFINET. When migrating to an S7 platform, PROFIBUS DP and PROFINET connectivity are introduced through the new S7 CPU’s integrated interfaces or via CP modules such as the CP342-5 or CP343-1. Existing SINEC H1 network segments can be bridged or replaced during the migration, and field device communication protocols should be mapped and validated before cutover.

Q3: How much physical space is required in the control cabinet for a migration project?
For a direct replacement, no additional cabinet space is needed — the 6ES5926-3KA12 occupies the existing CPU slot in the S5-115U rack. For a parallel migration approach (running S5 and S7 simultaneously during transition), additional DIN rail space of approximately 300–500 mm width is typically required for the S7-300 rack, power supply, and communication modules. Cabinet thermal management should be reviewed if additional modules increase heat dissipation. TOPNLMS can advise on component selection to optimize cabinet space utilization during the migration phase.

Q4: What programming tools are needed to work with the 6ES5926-3KA12, and are they still available?
The 6ES5926-3KA12 is programmed using SIMATIC STEP 5 software, which runs on Windows XP/7 (32-bit) environments or via virtual machine on modern hardware. Siemens continues to provide STEP 5 under a maintenance license for legacy system support. Program transfer to the CPU is performed via the PG/PC interface using a PC Adapter USB A2 or a dedicated S5 programming cable connected to the CPU’s programming port. For migration projects, the STEP 5 program can be exported and partially converted using Siemens’ S5-S7 Converter tool as a starting point for STEP 7 or TIA Portal re-engineering.

Warranty Assurance

Every Siemens 6ES5926-3KA12 unit supplied by TOPNLMS is covered by a 12-month warranty from the date of shipment. Prior to dispatch, each unit undergoes a structured pre-shipment inspection protocol that includes visual examination for physical damage, connector integrity verification, firmware version confirmation, and functional power-on testing where applicable. Units that do not pass inspection are quarantined and not shipped.

In the event of a warranty claim, TOPNLMS provides a replacement unit or full refund within the warranty period, subject to inspection of the returned item. Our technical support team is available to assist with installation verification, compatibility confirmation, and troubleshooting during the warranty period at no additional charge. For time-critical production environments, expedited replacement dispatch can be arranged upon request.

TOPNLMS maintains a dedicated inventory of SIMATIC S5 legacy components to support long-term procurement planning for facilities that operate extended S5 system lifecycles. Bulk procurement, scheduled delivery agreements, and multi-SKU sourcing packages are available for MRO and project procurement teams. All units are sourced through verified supply channels and are accompanied by documentation supporting traceability requirements.

For pricing, availability confirmation, technical compatibility questions, or migration project support, contact our industrial automation specialists directly.