Product Description

Siemens 3RH1921-1CD01 Auxiliary Contact Block – 1 NC, Front Mounting

The Siemens 3RH1921-1CD01 is a front-mounted auxiliary contact block from the Siemens SIRIUS accessory range, designed for compatible 3RT1 contactors in sizes S6 to S12. It provides 1 normally closed (NC) instantaneous auxiliary contact and is designed for snap-on front mounting with a screw-terminal connection. Siemens' SIRIUS catalog identifies this exact article as a one-pole front auxiliary switch for S6 to S12 contactors.

The accessory provides an additional auxiliary switching path for contactor feedback, interlocking, signalling and control applications without changing the main power-switching function of the connected contactor.

Siemens SIRIUS Auxiliary Contact Block

The 3RH1921-1CD01 is designed to expand the auxiliary functionality of large Siemens SIRIUS contactors.

Auxiliary contacts can be used independently of the main power contacts for:

• Contactor status feedback

• Electrical interlocking

• PLC input signals

• Control-circuit logic

• Machine sequencing

• Auxiliary signalling

• Motor-control circuits

• Industrial automation

Siemens identifies the 3RH1921 family as auxiliary switches for compatible 3RT1.5 to 3RT1.7 contactors, corresponding to the S6 to S12 sizes.

1 NC Auxiliary Contact

The 3RH1921-1CD01 provides 1 normally closed (NC) auxiliary contact.

The contact is instantaneous and provides an additional NC switching path for applications such as:

• Electrical interlocking

• Contactor status monitoring

• PLC feedback

• Auxiliary signalling

• Machine-control logic

• Relay circuits

• Control-system feedback

The Siemens catalog identifies this article as the 1 NC version within the one-pole auxiliary-switch range.

Front-Snap Mounting

The 3RH1921-1CD01 is designed for snapping onto the front of compatible SIRIUS contactors.

This mounting arrangement allows an additional auxiliary contact to be added directly to the contactor while maintaining a compact panel layout. Siemens specifically categorizes it among the one-pole auxiliary switches for snapping onto the front, sizes S6 to S12.

The front-mount design is useful for:

• Large motor starters

• Machine-control panels

• Automation cabinets

• OEM equipment

• Industrial electrical assemblies

Compatibility with S6 to S12 Contactors

The 3RH1921-1CD01 is intended for compatible Siemens 3RT1 contactors in S6 to S12 sizes. The Siemens catalog associates the one-pole auxiliary-switch family with 3RT1.5 through 3RT1.7 contactors.

The exact compatibility should be verified against the complete contactor article number before installation.

Screw-Terminal Connection

The 3RH1921-1CD01 uses a screw-terminal connection for the auxiliary circuit.

This provides a conventional wiring method for electrical panel builders and maintenance teams and is suitable for industrial control-panel installations. Siemens catalogs the screw-terminal version separately from the spring-loaded version.

Instantaneous Auxiliary Switching

The contact in the 3RH1921-1CD01 is an instantaneous NC auxiliary contact.

It follows the switching state of the associated contactor without incorporating an independent timing delay.

This makes it suitable for:

• Immediate interlocking

• Status indication

• Contactor monitoring

• PLC feedback

• Auxiliary signalling

• Machine-control logic

Industrial Automation Applications

The 3RH1921-1CD01 can expand the control functionality of compatible large-frame SIRIUS contactors.

Motor Control

The NC contact can be used in motor-starter interlocking and contactor-status circuits.

PLC Systems

The auxiliary contact can provide status information to a suitable PLC digital input.

Machine Control

The NC contact can support sequencing, interlocking and control logic.

Industrial Control Panels

The front-mount design provides a compact method of adding auxiliary functionality directly to a large contactor.

Automation Systems

The additional NC switching path can provide feedback and signalling within automated industrial equipment.

Suitable for OEMs and Panel Builders

The 3RH1921-1CD01 is suitable for OEM machine manufacturers, electrical panel builders, automation integrators and industrial maintenance professionals working with Siemens SIRIUS large-frame contactors.

Its 1 NC configuration, front mounting and screw-terminal connection make it useful where one additional normally closed auxiliary signal is required.

Key Features

• Siemens SIRIUS auxiliary contact block

• Article number 3RH1921-1CD01

• Front-snap mounting

• 1 NC auxiliary contact

• One-pole configuration

• Instantaneous contact

• Screw-terminal connection

• Suitable for S6 to S12 contactors

• Compatible with applicable 3RT1.5 to 3RT1.7 contactors

• Suitable for PLC feedback

• Suitable for electrical interlocking

• Suitable for machine-control applications

• Suitable for industrial automation

Benefits

• 1 NC contact: Provides an additional normally closed switching path.

• Front mounting: Allows direct installation onto compatible SIRIUS contactors.

• Instantaneous operation: The auxiliary contact follows the operating state of the associated contactor.

• Screw connection: Provides a familiar industrial wiring method.

• S6–S12 compatibility: Designed for large-frame SIRIUS contactor assemblies.

• Interlocking support: Useful for suitable electrical interlocking circuits.

• PLC integration: Can provide auxiliary contactor-status information.

• Compact design: Adds auxiliary functionality without requiring a separate external relay.

Why Choose Siemens 3RH1921-1CD01?

The Siemens 3RH1921-1CD01 provides a straightforward solution for adding one instantaneous normally closed auxiliary contact to compatible Siemens SIRIUS S6 to S12 contactors.

Its front-snap mounting, one-pole 1 NC configuration and screw-terminal connection make it suitable for applications requiring additional feedback, signalling, interlocking and machine-control functionality. Siemens' catalog specifically lists this article within the front-mounted S6 to S12 auxiliary-switch range.

Delivery Across India

SB Smart supplies Siemens industrial electrical and automation products across Faridabad, Gurgaon/Gurugram, Delhi NCR, Haryana, Noida, Punjab, Mumbai and 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

Frequently Asked Questions

1. What is Siemens 3RH1921-1CD01?

It is a Siemens SIRIUS front-mounted auxiliary contact block with 1 normally closed instantaneous contact for compatible S6 to S12 contactors.

2. How many auxiliary contacts does it provide?

It provides 1 NC auxiliary contact.

3. Is the contact instantaneous?

Yes. It is an instantaneous NC auxiliary contact.

4. How is it mounted?

It is designed for snap-on front mounting on compatible SIRIUS contactors.

5. Which contactors are compatible?

The product family is intended for compatible 3RT1 contactors in S6 to S12 sizes, including the relevant 3RT1.5 to 3RT1.7 range.

6. What type of terminal does it use?

The 3RH1921-1CD01 is the screw-terminal version of this auxiliary contact configuration.

7. What can the NC contact be used for?

It can be used for PLC feedback, signalling, electrical interlocking, contactor monitoring and machine-control logic.

8. Does it switch the main electrical load?

No. It is an auxiliary contact block; the main load is switched by the compatible contactor.

9. Is it suitable for large industrial control panels?

Yes. It is designed for compatible S6 to S12 SIRIUS contactors used in large industrial switching applications.

10. Where can I buy Siemens 3RH1921-1CD01 in India?

You can explore the Siemens industrial automation and electrical product range at SB Smart for auxiliary contact blocks, contactors and related control components.