Product Description

Siemens 3RH1921-1CA01 Auxiliary Contact Block – 1 NC, Front Mounting, S6-S12

The Siemens 3RH1921-1CA01 is a front-mounted auxiliary contact block from the Siemens SIRIUS 3RH19 accessory range, designed for compatible 3RT1 contactors. It provides 1 normally closed (1 NC) instantaneous auxiliary contact, uses screw-terminal connections, and is designed to snap onto the front of compatible contactors. Siemens currently lists this article as an active product.

Siemens SIRIUS Auxiliary Contact Block

The 3RH1921-1CA01 provides an additional auxiliary switching path for industrial control and automation systems.

It can be used for:

• Contactor status feedback

• Electrical interlocking

• PLC input signals

• Auxiliary signalling

• Machine sequencing

• Control-circuit logic

• Motor-control circuits

• Industrial automation

Siemens specifies this auxiliary switch for compatible 3RT10, 3RT12, 3RT145, 3RT146 and 3RT147 contactors.

1 NC Instantaneous Auxiliary Contact

The 3RH1921-1CA01 provides 1 normally closed instantaneous auxiliary contact and no NO or changeover contacts.

The NC contact can be used for:

• Contactor interlocking

• Status monitoring

• PLC feedback

• Auxiliary signalling

• Machine-control logic

• Relay circuits

• Control-system feedback

Because it is an instantaneous contact, its switching state follows the associated contactor without an intentional timing delay.

Front-Snap Mounting

The 3RH1921-1CA01 is designed for snap-on mounting at the front of compatible Siemens SIRIUS contactors. Siemens' technical data explicitly identifies the mounting method as snap-on.

This allows an additional auxiliary contact to be added directly to the contactor without requiring a separate external relay.

The front-mounted design is useful for:

• Large motor starters

• Industrial control panels

• Automation cabinets

• OEM machinery

• Machine-control systems

Compatibility with 3RT1 Contactors

The product is intended for compatible 3RT1 contactors, including the Siemens 3RT10, 3RT12, 3RT145, 3RT146 and 3RT147 families.

For the S6-S12 application described for this product family, the exact compatibility should always be verified against the complete contactor article number before installation.

Screw-Terminal Connection

The 3RH1921-1CA01 uses screw-type terminals for the auxiliary circuit. Siemens specifies compatible conductor sizes of 0.5 to 2.5 mm² for the auxiliary contacts.

This provides a familiar wiring method for electrical panel builders and maintenance teams.

Auxiliary Contact Ratings

The Siemens datasheet specifies an insulation voltage of 690 V and surge voltage resistance of 6 kV. For AC-15, the specified operational current is 6 A at 24 V and 230 V, and 3 A at 400 V.

For AC-12, the auxiliary contact is specified up to 10 A at 24 V and 230 V. The actual application must be selected according to the applicable utilization category and electrical rating.

Mirror Contact Function

When used with a compatible 3RT1 contactor, Siemens specifies the auxiliary switch as having a mirror contact function according to IEC 60947-4-1.

This feature can be useful for appropriate contact-state monitoring applications. Any safety-related function must be designed and validated as part of the complete machine safety system.

Industrial Automation Applications

The 3RH1921-1CA01 can expand the auxiliary functionality of compatible SIRIUS contactors.

Motor Control

The NC contact can be used in motor-starter interlocking and contactor-state 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 arrangement provides a compact way to add auxiliary functionality directly to the contactor.

Automation Systems

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

Suitable for OEMs and Panel Builders

The 3RH1921-1CA01 is suitable for OEM machine manufacturers, electrical panel builders, automation integrators and industrial maintenance professionals.

Its combination of 1 NC instantaneous contact, front snap-on mounting and screw terminals makes it useful where one additional normally closed auxiliary signal is required.

Key Features

• Siemens SIRIUS 3RH19 auxiliary contact block

• Article number 3RH1921-1CA01

• Front-mounted design

• Snap-on mounting

• 1 NC instantaneous contact

• Screw terminals

• Compatible with selected 3RT1 contactors

• Suitable for PLC feedback

• Suitable for electrical interlocking

• Suitable for machine-control applications

• Suitable for industrial automation

• Mirror-contact function with 3RT1 according to IEC 60947-4-1

Benefits

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

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

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

• Screw terminals: Provides a familiar industrial wiring method.

• PLC integration: Supports contactor-status monitoring.

• Interlocking support: Useful in suitable electrical interlocking circuits.

• Compact design: Helps maintain an organized control-panel layout.

• Easy expansion: Adds auxiliary functionality without replacing the main contactor.

Why Choose Siemens 3RH1921-1CA01?

The Siemens 3RH1921-1CA01 provides a straightforward solution for adding one instantaneous normally closed auxiliary contact to compatible Siemens SIRIUS 3RT1 contactors.

Its front snap-on mounting, 1 NC configuration and screw-terminal connection make it suitable for additional feedback, signalling, interlocking and machine-control functions. Siemens currently lists the article as an active product.

For OEMs, panel builders and automation integrators, it provides a compact way to expand auxiliary control functionality in industrial contactor assemblies.

Delivery Across India

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

Frequently Asked Questions

1. What is Siemens 3RH1921-1CA01?

It is a Siemens SIRIUS front-mounted auxiliary contact block with 1 normally closed instantaneous contact for compatible 3RT1 contactors.

2. How many auxiliary contacts does it provide?

It provides 1 NC auxiliary contact.

3. Is the contact instantaneous?

Yes. Siemens specifies 1 instantaneous NC contact.

4. How is it mounted?

It is designed for snap-on front mounting.

5. What type of terminal does it use?

It uses screw-type terminals.

6. Which Siemens contactors are compatible?

Siemens specifies it for 3RT10, 3RT12, 3RT145, 3RT146 and 3RT147 contactors.

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. Does it provide a mirror contact function?

Yes. When used with a compatible 3RT1 contactor, Siemens specifies mirror-contact functionality according to IEC 60947-4-1.

10. Where can I buy Siemens 3RH1921-1CA01 in India?

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