SITOP

Siemens SITOP is the industrial power supply product line, providing regulated 24 V DC output power for SIMATIC control systems, distributed I/O, field instruments, sensors, and other 24 V DC loads in industrial automation panels. SITOP supplies convert single-phase or three-phase AC input to stable 24 V DC, and are used wherever consistent, regulated DC power is required within a control cabinet or across a distributed automation system. A failed or unstable SITOP power supply can affect an entire control system, since the SIMATIC PLC, I/O modules, and connected field devices that depend on 24 V DC will all lose power simultaneously. Maintenance teams managing production-critical systems often keep SITOP spares on hand for rapid exchange when a power supply fails. 

PLC Direct supplies Siemens SITOP power supplies and accessories to customers for maintenance and replacement in existing SITOP installations. Our collection covers single-phase and three-phase power supply modules, selectivity modules, and UPS battery modules across the PSU100S, PSU300S, and SITOP modular product ranges. 

Where Siemens SITOP Power Supplies Are Used 

SITOP power supplies are a standard component in SIMATIC control panels across virtually every industrial sector. They are found wherever a 24 V DC bus needs to be reliably supplied from an AC source. 

Applications and facilities that rely on Siemens SITOP power supplies include: 

• SIMATIC S7 control panels in manufacturing, automotive, and process industries 

• Distributed ET 200 I/O installations requiring a local 24 V DC supply 

• Machine tool control cabinets powered from a single-phase 120/230 V AC supply 

• Process plant panels requiring three-phase AC input for higher power output 

• Water and wastewater control systems with redundant power requirements 

• Mining and heavy industry panels in harsh environments with 24 V DC distribution needs 

• Building and infrastructure automation panels with multiple 24 V DC load branches 

Siemens SITOP Products 

The SITOP collection at PLC Direct covers single-phase and three-phase stabilized power supply modules, selectivity modules for branch circuit protection, and UPS battery modules for backup power. All product families and part number references below are confirmed on the live PLC Direct collection page. 

Product Families 

• SITOP PSU100S (1-phase, 24 V DC): Single-phase stabilized power supplies with 120/230 V AC input and 24 V DC output. The 20 A variant (6EP1336-2BA10) and the 10 A variant (6EP1334-2BA20) are both confirmed active products in stock. These supply 24 V DC directly from single-phase mains for SIMATIC and field device loads. 

• SITOP PSU300S (3-phase, 24 V DC): Three-phase stabilized power supplies with 400-500 V 3 AC input and 24 V DC output for higher-power applications. The 40 A variant (6EP1437-2BA20) is confirmed in stock and provides 24 V DC / 40 A output from a three-phase supply. 

• SITOP Modular: Higher-capacity modular power supply in the SITOP range. The 20 A modular unit (6EP1436-3BA00) accepts 400-500 V 3 AC input and delivers 24 V DC / 20 A output. This unit carries announcement-of-phase-out lifecycle status. 

• SITOP PSE200U Selectivity Module: A downstream selectivity module for distributing 24 V DC from a single SITOP supply to multiple independent load branches. The 4-channel 10 A per channel unit (6EP1961-2BA21) accepts 24 V DC / 40 A input and distributes to four 24 V DC / 10 A output channels with adjustable threshold (3-10 A) and common signaling contact. Confirmed in stock. 

• SITOP UPS1100 Battery Module: Replacement battery module for SITOP DC UPS systems. The 24 V DC / 3.2 Ah sealed lead-acid battery module (6EP4133-0GB00-0AY0) is the replacement battery for SITOP UPS1100 DC UPS units. This module is at the start-of-final-year-of-support lifecycle status. 

Available at PLC Direct 

• SITOP PSU100S 20 A, 120/230 V AC input, 24 V DC / 20 A output (6EP1336-2BA10) 

• SITOP PSU100S 10 A, 120/230 V AC input, 24 V DC / 10 A output (6EP1334-2BA20) 

• SITOP PSU300S 40 A, 400-500 V 3 AC input, 24 V DC / 40 A output (6EP1437-2BA20) 

• SITOP Modular 20 A, 400-500 V 3 AC input, 24 V DC / 20 A output (6EP1436-3BA00) 

• SITOP PSE200U 4-channel selectivity module, 24 V DC / 4x10 A, threshold 3-10 A (6EP1961-2BA21) 

• SITOP UPS1100 replacement battery module, 24 V DC / 3.2 Ah sealed lead-acid (6EP4133-0GB00-0AY0) 

What to Know Before You Buy Siemens SITOP Parts 

Selecting the correct SITOP power supply requires matching the input voltage (single-phase or three-phase, and the specific voltage range), the output current rating, and the installed form factor. 

Hardware condition options: We supply SITOP power supplies as surplus sealed, refurbished, and used. Surplus sealed units are factory-sealed stock. Refurbished units have been tested and restored to operational condition. 

Input voltage: SITOP PSU100S units accept single-phase 120/230 V AC. SITOP PSU300S and SITOP Modular units require three-phase 400-500 V 3 AC input. Confirm the available mains supply before selecting a unit. 

Output current rating: SITOP power supplies are rated by output current at 24 V DC. Select a unit with an output current rating that matches or exceeds the total 24 V DC load, with appropriate derating for elevated ambient temperatures. 

Selectivity modules: The SITOP PSE200U selectivity module is not a power supply itself. It accepts 24 V DC input from an upstream SITOP supply and distributes it to independent load branches, providing branch-level overcurrent protection without triggering the main supply. It is used downstream of a primary SITOP supply in systems with multiple 24 V DC load groups. 

Lifecycle considerations: The SITOP Modular 20 A unit and UPS1100 battery module carry phase-out or final-year-of-support status. Stocking a spare now avoids a sourcing gap when these parts are no longer available through any channel. 

Warranty: All Siemens SITOP hardware purchased from PLC Direct includes a standard 1-year warranty covering defects and functionality, applicable to surplus sealed, refurbished, and used products.