Product Description

Siemens 3RH1921-1CA10 Auxiliary Contact Block – 1 NO, Front Mounting

The Siemens 3RH1921-1CA10 is a front-mounted auxiliary contact block from the Siemens SIRIUS 3RH19 accessory range, designed for compatible 3RT1 contactors. It provides 1 normally open (1 NO) instantaneous auxiliary contact with a screw-terminal connection and snap-on front mounting. Siemens' current Industry Mall identifies this exact article as an active front-side auxiliary switch for 3RT1 contactors.

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

Siemens SIRIUS Auxiliary Contact Block

The 3RH1921-1CA10 is designed to expand the auxiliary functionality of compatible Siemens SIRIUS contactors.

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

• Contactor status feedback

• PLC input signals

• Auxiliary signalling

• Electrical interlocking

• Machine sequencing

• Control-circuit logic

• Motor-control circuits

• Industrial automation

Siemens identifies the product as a front-side auxiliary switch for 3RT1 contactors, with suitability including 3RT10, 3RT12, 3RT145, 3RT146 and 3RT147 contactor families.

1 NO Auxiliary Contact

The 3RH1921-1CA10 provides 1 normally open (NO) instantaneous auxiliary contact.

The contact closes when the associated contactor operates, making it useful for additional control and monitoring functions.

Typical applications include:

• Contactor ON feedback

• PLC monitoring

• Auxiliary relay logic

• Status indication

• Machine sequencing

• Control-system feedback

• Electrical interlocking

• Auxiliary signalling

Siemens specifies 1 NO contact and 0 NC or changeover contacts for this article.

Front-Snap Mounting

The 3RH1921-1CA10 is designed for snapping onto the front of compatible Siemens SIRIUS contactors.

This allows the auxiliary contact block to be installed directly on the contactor while keeping the panel assembly compact and organized.

The product is categorized by Siemens as a front-side auxiliary switch for 3RT1 contactors.

Typical applications include:

• Motor starters

• Machine-control panels

• Industrial control cabinets

• Automation systems

• OEM machinery

• Electrical contactor assemblies

Compatibility with S6 to S12 Contactors

The 3RH1921-1CA10 is included in the Siemens one-pole front-mounted auxiliary-contact range for S6 to S12 contactors, corresponding to compatible 3RT1.5 to 3RT1.7 applications. Siemens catalog information places this article in the S6-S12 front-mounted auxiliary-contact category.

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

Screw-Terminal Connection

The 3RH1921-1CA10 uses a screw-terminal connection for the auxiliary circuit. Siemens identifies the product specifically as a 1 NO contact, screw terminal auxiliary switch.

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

The connection method supports practical installation, commissioning and servicing of auxiliary control circuits.

Instantaneous Auxiliary Switching

The contact in the 3RH1921-1CA10 is instantaneous.

There is no independent time-delay function. The auxiliary contact follows the operating state of the associated contactor.

This makes it suitable for:

• Immediate contactor feedback

• PLC monitoring

• Status indication

• Interlocking

• Machine-control logic

• Auxiliary signalling

Siemens classifies the product family as Instantaneous.

Auxiliary Contact Capacity

The 3RH1921-1CA10 is intended for auxiliary control and signalling rather than primary power switching.

The current Siemens datasheet specifies auxiliary-contact operating values such as up to 10 A at AC-12 at 24 V and 230 V, with lower values applying for other utilization categories and voltages.

The actual connected circuit must always be designed according to the applicable utilization category, voltage and contact rating.

Industrial Automation Applications

The 3RH1921-1CA10 can expand the control functionality of compatible large-frame Siemens contactors.

Motor Control

The NO contact can provide contactor-status feedback within motor starters and control panels.

PLC Systems

The auxiliary contact can be connected to a suitable PLC digital input for monitoring contactor operation.

Machine Control

The NO contact can support machine sequencing, status logic and auxiliary control.

Industrial Control Panels

The front-mounted design provides a compact way of adding an auxiliary switching path directly to the contactor.

Automation Systems

The additional NO contact can provide feedback and signalling within automated industrial equipment.

Suitable for OEMs and Panel Builders

The 3RH1921-1CA10 is suitable for OEM machine manufacturers, electrical panel builders, automation integrators and industrial maintenance professionals working with compatible Siemens SIRIUS contactors.

Its 1 NO configuration, front mounting and screw-terminal connection make it useful where one additional instantaneous auxiliary signal is required.

Key Features

• Siemens SIRIUS 3RH19 auxiliary contact block

• Article number 3RH1921-1CA10

• Front-mounted auxiliary switch

• Snap-on front mounting

• 1 NO auxiliary contact

• Instantaneous contact operation

• Screw-terminal connection

• Suitable for compatible 3RT1 contactors

• Included in the S6-S12 front-mounted auxiliary-contact range

• Suitable for PLC feedback

• Suitable for electrical interlocking

• Suitable for machine-control applications

• Suitable for industrial automation

Benefits

• 1 NO contact: Provides an additional normally open switching path.

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

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

• Screw terminals: Provides a familiar industrial wiring method.

• PLC integration: Supports contactor-status monitoring.

• Control flexibility: Useful for signalling, sequencing and feedback.

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

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

Why Choose Siemens 3RH1921-1CA10?

The Siemens 3RH1921-1CA10 provides a straightforward solution for adding one instantaneous normally open auxiliary contact to compatible Siemens SIRIUS 3RT1 contactors.

Its front-snap mounting, 1 NO configuration and screw-terminal connection make it suitable for applications requiring additional contactor feedback, signalling, interlocking and machine-control functionality.

Siemens currently lists the 3RH1921-1CA10 as an active product and identifies it specifically as a front-side 1 NO auxiliary switch with screw terminal for 3RT1 contactors.

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 3RH1921-1CA10?

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

2. How many auxiliary contacts does it provide?

It provides 1 NO auxiliary contact.

3. Is the contact instantaneous?

Yes. It is an instantaneous NO auxiliary contact.

4. How is it mounted?

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

5. What type of terminal does it use?

It uses a screw-terminal connection.

6. Which Siemens contactors are compatible?

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

7. Is it suitable for S6-S12 contactors?

Yes. Siemens catalog listings place the 3RH1921-1CA10 in the one-pole front-mounted auxiliary-contact range for S6-S12 / 3RT1.5-3RT1.7 contactors.

8. What can the NO contact be used for?

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

9. Does it switch the main electrical load?

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

10. Where can I buy Siemens 3RH1921-1CA10 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.