The Siemens 3RH2122-1BB408K is a SIRIUS 3RH2 auxiliary contactor / contactor relay designed for industrial control, automation, signalling and interlocking applications. It features mechanically linked contact elements, 2 normally open (NO) and 2 normally closed (NC) contacts, a 24 V DC coil, screw-terminal connections and a compact S00 frame size.
The corresponding Siemens 3RH2122-1BB40 configuration is a four-pole S00 contactor relay with a 22E contact arrangement and 24 V DC control voltage, making it suitable for auxiliary and control circuits in industrial automation systems.
The 3RH2122-1BB408K is intended for switching auxiliary and control circuits rather than directly switching high-power motor loads.
It can be used to transfer control signals, provide feedback, implement interlocking and support machine-control logic.
Typical applications include:
Industrial automation
Machine-control panels
PLC interface circuits
Motor-control circuits
Electrical interlocking
Signalling systems
Process automation
OEM machinery
Control cabinets
Auxiliary switching
A key feature of the 3RH2122-1BB408K is its mechanically linked contact elements.
Mechanical linkage maintains a defined relationship between the contact elements and can be useful in control circuits where contact-state monitoring is important.
Potential applications include:
Contactor status monitoring
Electrical interlocking
PLC feedback
Machine sequencing
Diagnostic circuits
Control logic
Suitable safety-related control architectures
For safety-related applications, the complete safety function must be designed and validated as part of the overall machine-control system.
The corresponding 3RH2122-1BB40 configuration provides 2 normally open and 2 normally closed contacts.
This 22E contact arrangement provides multiple auxiliary switching paths for:
Contactor feedback
PLC inputs
Electrical interlocking
Relay logic
Machine sequencing
Status signalling
Auxiliary switching
Control-system feedback
The contacts should always be operated within their specified electrical ratings.
The 3RH2122-1BB408K uses a 24 V DC control coil.
This makes it suitable for industrial control systems that use 24 V DC control circuits, including compatible PLC and automation architectures.
The control voltage must always be matched to the exact product marking and the requirements of the installation.
The 3RH2122-1BB408K uses screw-terminal connections, providing a familiar wiring method for industrial control panels.
This connection style is suitable for panel builders and maintenance teams working with conventional auxiliary-control wiring.
The relay is a Size S00 device, providing a compact solution for electrical cabinets where control-panel space is important.
It can be integrated into:
Control cabinets
Automation panels
Machine-control stations
OEM equipment
Relay and contactor assemblies
The 3RH2122-1BB408K can be integrated with:
PLCs
HMIs
Motor contactors
Overload relays
Circuit breakers
Pushbuttons
Selector switches
Sensors
Safety components
Other Siemens SIRIUS devices
Its 2 NO + 2 NC configuration allows multiple control, feedback and interlocking functions from a single compact auxiliary contactor.
The Siemens 3RH2122-1BB408K can be used for:
Industrial automation
Motor-control panels
PLC signal interfacing
Electrical interlocking
Machine sequencing
Production machinery
Process automation
Conveyor-control systems
Pump-control circuits
OEM control panels
Industrial signalling
Auxiliary switching
For related Siemens industrial electrical and automation products, customers can explore the Siemens product range at SB Smart.
The 3RH2122-1BB408K is suitable for OEM machine manufacturers, electrical panel builders, automation integrators and industrial maintenance professionals.
Its combination of mechanically linked contact elements, 2 NO + 2 NC contacts, 24 V DC coil, screw terminals and compact S00 design makes it suitable for control and signalling applications where reliable auxiliary switching is required.
Siemens SIRIUS 3RH2 auxiliary contactor
Article number 3RH2122-1BB408K
Mechanically linked contact elements
2 NO + 2 NC contacts
24 V DC coil
Screw terminals
Size S00
22E contact arrangement
Suitable for electrical interlocking
Suitable for PLC feedback
Suitable for machine sequencing
Suitable for industrial automation
Suitable for OEM control panels
Mechanically linked contacts: Supports reliable contact-state relationships for suitable monitoring and control applications.
2 NO + 2 NC contacts: Provides multiple auxiliary switching paths.
24 V DC coil: Suitable for common industrial DC control architectures.
Screw terminals: Provides a familiar industrial wiring method.
Compact S00 size: Helps optimize control-panel space.
Flexible control logic: Supports feedback, interlocking, signalling and sequencing.
Automation integration: Suitable for PLC-based control systems.
OEM-friendly: Suitable for standardized machine-control panel designs.
The Siemens 3RH2122-1BB408K combines mechanically linked contact elements, 2 NO + 2 NC auxiliary contacts, a 24 V DC control coil and screw-terminal connections in a compact S00 auxiliary contactor.
Its configuration is suitable for industrial control applications requiring reliable auxiliary switching, feedback, interlocking and signalling.
For OEMs, panel builders and automation integrators, it provides a practical solution for control circuits where both NO and NC auxiliary contacts are required.
SB Smart supplies Siemens industrial electrical and automation products across Faridabad, Gurgaon/Gurugram, Delhi NCR, Haryana, Noida, Punjab, Mumbai and all major cities across India.
Major delivery locations include:
Faridabad
Gurgaon/Gurugram
Delhi
Delhi NCR
Noida
Greater Noida
Haryana
Punjab
Mumbai
Pune
Ahmedabad
Bengaluru
Hyderabad
Chennai
Kolkata
Jaipur
Chandigarh
Lucknow
Indore
Surat
Vadodara
Nagpur
Coimbatore
And other major cities across India
It is a Siemens SIRIUS 3RH2 auxiliary contactor/contact relay with mechanically linked contacts, 2 NO + 2 NC contacts and a 24 V DC coil.
It provides 2 normally open and 2 normally closed contacts.
The specified control coil is 24 V DC.
Yes. The product uses screw-terminal connections.
It is a compact S00-size contactor relay.
They can support contact-state monitoring, interlocking, diagnostics and suitable safety-related control functions within a correctly designed system.
Yes. Its auxiliary contacts can be incorporated into suitable PLC feedback and control circuits, provided the electrical ratings are compatible.
It is an auxiliary contactor/contact relay intended primarily for control and auxiliary circuits rather than direct high-power motor switching.
It can be used in industrial automation, machine-control panels, PLC interfaces, interlocking systems, production machinery and OEM control cabinets.
You can explore the Siemens product range at SB Smart for Siemens contactor relays, auxiliary contact blocks, contactors and other industrial automation products.
| Specification | Details |
|---|---|
| Product Name | Auxiliary Contactor Relay |
| Brand | Siemens |
| Series | SIRIUS 3RH2 |
| Model Number | 3RH2122-1BB408K |
| SKU | 3RH2122-1BB408K |
| Product Type | Auxiliary Contactor |
| Frame Size | S00 |
| Contact Configuration | 2NO + 2NC |
| Number of Normally Open Contacts | 2 |
| Number of Normally Closed Contacts | 2 |
| Contact Design | Mechanically Linked Contact Elements |
| Coil Voltage | 24V DC |
| Control Voltage Type | DC |
| Coil Power Consumption | 4 W |
| Operating Voltage Range | 0.8 – 1.1 × Rated Voltage |
| Connection Type | Screw Terminals |
| Mounting Type | DIN Rail / Panel Mount |
| Rated Operational Current AC-12 | 10 A |
| Rated Operational Current AC-15 (230V) | 10 A |
| Rated Operational Current AC-15 (400V) | 3 A |
| Rated Operational Current AC-15 (500V) | 2 A |
| Rated Operational Current AC-15 (690V) | 1 A |
| Rated Insulation Voltage (Ui) | 690 V |
| Rated Impulse Withstand Voltage (Uimp) | 6 kV |
| Mechanical Endurance | Up to 30 Million Operations |
| Operating Temperature | -25°C to +60°C |
| Storage Temperature | -55°C to +80°C |
| Degree of Protection | IP20 |
| Width | 45 mm |
| Height | 57.5 mm |
| Depth | 73 mm |
| Standards Compliance | IEC 60947-1, IEC 60947-4-1, IEC 60947-5-1 |
| Safety Function Suitable | Yes |
| Product Family | Siemens SIRIUS Auxiliary Contactors |
No reviews yet.