Product Description

Siemens 3RH2921-1DA02 Auxiliary Contact Block – Lateral Mounting, 2 NC

The Siemens 3RH2921-1DA02 is a laterally mountable auxiliary contact block from the Siemens SIRIUS accessory range, designed for compatible 3RT2 contactors and 3RH2 contactor relays. It provides 2 normally closed (2 NC) auxiliary contacts and uses screw-terminal connections. Siemens specifies this article for lateral mounting on compatible devices, with the contact numbering depending on whether it is mounted on the left or right side.

Siemens SIRIUS Auxiliary Contact Block

The 3RH2921-1DA02 is an accessory used to add additional auxiliary switching capability to compatible Siemens SIRIUS contactors and contactor relays.

Auxiliary contacts are useful for control, feedback, signalling and interlocking without changing the main power-switching function of the connected contactor.

Typical applications include:

• Contactor status feedback

• PLC input signals

• Electrical interlocking

• Control-circuit logic

• Machine sequencing

• Auxiliary signalling

• Motor-control circuits

• Industrial automation

2 NC Auxiliary Contacts

The 3RH2921-1DA02 provides 2 normally closed (2 NC) auxiliary contacts. Siemens product data identifies the two instantaneous NC contact paths as 51/52 and 61/62 when mounted on the left, while the terminal identification changes for right-side mounting.

These contacts can be used for:

• Contactor interlocking

• Control-circuit logic

• PLC monitoring

• Auxiliary signalling

• Machine sequencing

• Status feedback

• Relay logic

The connected electrical circuit should always remain within the applicable contact ratings.

Lateral Mounting on Left and/or Right

The 3RH2921-1DA02 is designed as a laterally mountable auxiliary switch, allowing installation on the left and/or right side of compatible SIRIUS devices. Siemens' 2025 catalog lists the 3RH2921-1DA02 among the laterally attachable auxiliary switches for SIRIUS contactors and contactor relays.

This arrangement is useful when additional auxiliary contacts are required while maintaining an organized and compact control-panel layout.

Compatibility with 3RT2 and 3RH2 Devices

Siemens specifies the 3RH2921-1DA02 for compatible:

• 3RT2.2 contactors

• 3RT2.3 contactors

• 3RT2.4 contactors

• 3RH2 contactor relays

The exact compatibility should always be checked against the complete contactor or contactor-relay article number before installation.

Screw-Terminal Connections

The 3RH2921-1DA02 uses screw terminals for its auxiliary-contact connections. This provides a conventional wiring method for industrial control panels and is suitable for panel builders and maintenance teams.

Industrial Automation Applications

The auxiliary contact block can expand the control functionality of compatible contactors and contactor relays.

Motor Control

The NC contacts can be incorporated into motor-control and interlocking circuits.

PLC Systems

Auxiliary contacts can provide contactor status information to PLC digital inputs when appropriately configured.

Machine Control

The additional NC contacts can support sequence logic, interlocking and auxiliary control functions.

Industrial Control Panels

Its lateral mounting arrangement helps panel builders add auxiliary functionality without replacing the main contactor.

Automation Systems

The contacts can provide additional control and signalling paths within automated equipment.

Suitable for OEMs and Panel Builders

The 3RH2921-1DA02 is suitable for OEM machine manufacturers, electrical panel builders, automation integrators and industrial maintenance professionals.

Its 2 NC configuration, lateral mounting design and screw terminals make it a practical accessory for expanding the auxiliary functionality of compatible Siemens SIRIUS contactors and contactor relays.

Key Features

• Siemens SIRIUS auxiliary contact block

• Article number 3RH2921-1DA02

• Laterally mountable design

• Left/right side mounting capability

• 2 NC auxiliary contacts

• Screw-terminal connections

• Compatible with selected 3RT2 contactors

• Compatible with 3RH2 contactor relays

• Suitable for electrical interlocking

• Suitable for PLC feedback

• Suitable for machine-control applications

• Suitable for industrial automation

Benefits

• 2 NC contacts: Provides two additional normally closed switching paths.

• Lateral mounting: Allows the auxiliary block to be installed on the side of compatible devices.

• Compact panel integration: Helps make efficient use of control-panel space.

• Easy wiring: Screw terminals provide a familiar industrial connection method.

• Interlocking support: NC contacts are useful in suitable control and interlocking circuits.

• PLC integration: Can provide auxiliary status signals.

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

• Industrial suitability: Designed for Siemens SIRIUS control assemblies.

Why Choose Siemens 3RH2921-1DA02?

The Siemens 3RH2921-1DA02 provides a straightforward way to expand the auxiliary switching functionality of compatible 3RT2 contactors and 3RH2 contactor relays.

Its 2 NC contacts, lateral mounting arrangement and screw-terminal connections make it suitable for applications requiring additional interlocking, signalling, feedback or machine-control functions. Siemens identifies the article as an active laterally mountable 2 NC auxiliary switch for the compatible SIRIUS devices.

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 3RH2921-1DA02?

It is a laterally mountable auxiliary contact block for compatible Siemens 3RT2 contactors and 3RH2 contactor relays.

2. How many auxiliary contacts does it provide?

It provides 2 normally closed (2 NC) auxiliary contacts.

3. What are the contact paths?

For left-side mounting, Siemens identifies the NC paths as 51/52 and 61/62. The terminal identification changes according to the mounting side.

4. Can it be mounted laterally?

Yes. It is designed for lateral mounting on compatible Siemens SIRIUS devices.

5. Which devices are compatible?

Siemens specifies it for 3RT2.2, 3RT2.3, 3RT2.4 and 3RH2 devices.

6. Does it use screw terminals?

Yes. The auxiliary contact block uses screw-terminal connections.

7. What can the NC contacts be used for?

They can be used for interlocking, feedback, signalling, control logic and machine sequencing.

8. Does it switch the main load?

No. It provides auxiliary control and signalling contacts; the main electrical load is switched by the compatible contactor.

9. Is it suitable for OEM control panels?

Yes. It is suitable for OEM machinery, panel building, industrial automation and maintenance applications.

10. Where can I buy Siemens 3RH2921-1DA02 in India?

You can explore the Siemens product range at SB Smart for Siemens auxiliary contact blocks, contactors, relays and other industrial automation products.