Siemens 3SB3400-0C Screw Terminal Contact Block

3SB3400-0C: SIRIUS 3SB3 series, front panel mounted single contact block, 1NC (1 Normally Closed), screw terminal type. Designed for 22mm pushbuttons / selector switches, Positive Opening safety contact.

Product Status: Discontinued (PM490). Original manufacturer supply stopped. Recommended replacement model: 3SU1400-1AA10-1CA0 (SIRIUS ACT series)

Core Technical Data

Selection & Matching Guidelines

1. Cross reference of contact blocks in the same series

3SB3400-0B: 1NO (Single Normally Open)

3SB3400-0C: 1NC (Single Normally Closed, this model)

3SB3400-0A: 1NO+1NC (1 Changeover)

3SB3400-0D: 2NO; 3SB3400-0E: 2NC

2. Stacking Rule: One contact block occupies one mounting slot; max. 3 contact blocks for non-illuminated pushbuttons
3. Positive Opening Feature: This NC contact is a safety contact, suitable for E-Stop circuits and meets positive opening requirements for safety loops. Priority selection for emergency stop applications.

Application Scenarios

22mm pushbuttons, rotary switches and emergency stop signal collection in control cabinets

PLC digital input circuits, safety E-Stop loops, interlock circuits

Guard interlocks, equipment limit detection, fault alarm signals

Troubleshooting Guide

1. Low-level signal (5V/1mA): Contact oxidation shall be checked first. Although low-level reliability is specified, aged contacts may suffer poor contact.
2. Safety circuit: Positive opening NC contact must be used. Ordinary contacts are prohibited as substitutes. During maintenance, manually actuate pushbutton and verify reliable contact opening.
3. Wiring: Control tightening torque of screw terminals; loose connections cause signal jitter. Terminals IP20, metal dust prevention required inside cabinet terminal area.

Replacement Model Description

Direct OEM replacement: 3SU1400-1AA10-1CA0 (SIRIUS ACT,1NC, screw terminal, positive opening, 22mm pushbutton system).

Bases of old & new series cannot be interchanged. Full assembly replacement (actuator + base + contacts) is required when switching to 3SU1.

1. 3SB3 Pushbutton Assembly Selection Examples (Based on 3SB3400-0C 1NC Contact Block)

Core rule: 3SB3 adopts modular assembly: Actuator + Base Holder + Contact Block. Max. 3 contact blocks for non-illuminated pushbuttons; max.2 contact blocks for illuminated pushbuttons. Each contact block occupies one mounting slot.

Contact block list recap

3SB3400-0B:1NO

3SB3400-0C:1NC (this model, positive opening safety contact)

3SB3400-0A:1NO+1NC

3SB3400-0D:2NO; 3SB3400-0E:2NC

Example1: Mushroom Head Emergency Stop (Safety Circuit, Most Common for 3SB3400-0C)

Purpose: Equipment emergency stop, safety circuit positive opening NC

Actuator:3SB3000-1HA20 (Red mushroom head, twist reset)

Base holder:3SB3901-0AC (3-position holder)

Contact: 3SB3400-0C (1NC positive opening)

Complete factory pre-assembled part number:3SB3203-1HA20-0AC0 (factory pre-fitted with 1NC, no separate contact ordering required). Redundant safety circuit can add a second 3SB3400-0C for dual NC.

Example2: Red Momentary Pushbutton (Fault Acknowledge)

Purpose:Fault reset, PLC DI acquisition

Actuator:3SB3000-0AA21 (Red flat momentary button)

Holder:3SB3901-0AC (3-position holder)

Contact combination:3SB3400-0B (1NO) + 3SB3400-0C (1NC)

Function:NO for DI signal; NC for circuit fault verification

Example3: 2-position Selector Switch (0-I)

Purpose:Local/Remote mode switchover

Switch actuator:3SB3000-2CA11 (2-position latching selector switch)

Holder:3SB3901-0AC

Contact:3SB3400-0B (NO for I position) + 3SB3400-0C (NC for 0 position)

Example4: Illuminated Green Start Pushbutton

Restriction: Max.2 contact blocks for illuminated pushbuttons

Actuator:3SB3000-4AA31 (Green illuminated flat pushbutton)

Lamp holder:3SB3401-1A (LED lamp holder)

Contact:3SB3400-0B (1NO for start) + 3SB3400-0C (1NC for interlock)

1. Replacement List from Old 3SB3 to New SIRIUS ACT 3SU1

⚠️Important: 3SB3 and 3SU1 bases/contact blocks are completely non-interchangeable. Contacts cannot be replaced alone; full assembly replacement (actuator + base + contacts) is mandatory.

Original contact block 3SB3400-0C (1NC screw terminal, positive opening)

→ Corresponding contact: 3SU1400-1AA10-1CA0 (1NC, screw terminal, positive opening)

III. Assembly & Engineering Guidelines

1. Contact stacking sequence: Mount safety NC contact (3SB3400-0C) closest to panel side for best mechanical synchronization. Recommended for emergency stop safety circuits.
2. Torque: Screw terminal tightening torque 0.8~1.2 N·m. Loose connections lead to DI signal fluctuation; loose terminals strictly prohibited for safety circuits.
3. Low-level signal: PLC passive DI (5V/1mA). Use OEM contacts preferably. Aged contacts tend to oxidize, NC circuits more prone to intermittent conduction.
4. Panel cutout: Standard Φ22mm round hole; round 3SB3 panel thickness: 1～6 mm; square 3SB3 panel thickness: 1～4 mm.
5. Migration Notes During Model Replacement
6. Cabinet cutout unchanged, both Φ22mm, but front bezel profile differs. Deburr if old cutout edge corroded.
7. Terminal position changes after replacement, redraw terminal diagram to avoid wiring misconnection.
8. Safety circuit: New 3SU1 1NC contact also features positive opening, complies with EN 60947-5-1 and can directly replace original 3SB3400-0C for emergency stop applications.
9. Spare part strategy: 3SB3 series discontinued by OEM, only stock parts available on market. New projects adopt 3SU1 directly.

Siemens 3SB3400-0C Mounting Dimensions

This model is a single contact block (1NC) belonging to 3SB3 series modular 22mm pushbutton components. The contact block has no separate cutout, clipped onto 3SB3 holder (3SB3901-0AC). Complete pushbutton panel cutout Φ22mm.

Contact Block Physical Dimensions (mm)

Width: 10 mm (standard width of single contact block, each block occupies 10mm during stacking)

Height: 36.5 mm

Depth: 20 mm (from holder surface backward including screw terminals)

Single contact blocks (3SB3400-0B / 0C) share identical dimensions. Double contact blocks (3SB3400-0A/0D/0E) width =20mm.

Complete Pushbutton Assembly Dimensions (Holder + Contact Blocks)

1. Panel Cutout: Φ22 mm (standard 22mm pushbutton round hole)

Round pushbutton panel thickness: 1～6 mm

Square pushbutton panel thickness: 1～4 mm

2. 3-position holder 3SB3901-0AC: max. 3 single contact blocks stacked, total stacking width=3×10=30 mm
3. Cabinet rear depth:

1 contact block: ~42 mm (panel rear face to terminal end)

Fully loaded with 3 contact blocks: ~42 mm (depth unchanged, only lateral width increases)

Mounting Spacing Requirements

Center-to-center minimum distance between adjacent 22mm pushbuttons: 50mm (round type); min. 50mm for square 3SB3 pushbuttons

Reserved rear cabinet space: ≥45mm for wiring and terminal tightening

Dimension Comparison with Replacement Model 3SU1400-1AA10-1CA0 (3SU1 Contact Block)

Body dimension: W10mm × H36.5mm × D20mm, similar body size

⚠️Holder structure differs and cannot be directly interchanged. Panel cutout still Φ22mm but rear mounting profile is different.

Engineering Drawing Notes

1. Contact block is clip-on type, no fixing screws; slide and clip into holder rail.
2. Terminal screws protrude rearward. Reserve ≥45mm depth for cabinet layout.
3. Stacking sequence: Mount safety NC contact (3SB3400-0C) nearest to panel.