Product Description

Siemens 3RH2921-1DA20 Auxiliary Contact Block – Lateral Mounting, 2 NO

The Siemens 3RH2921-1DA20 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 open (2 NO) auxiliary contacts with screw-terminal connections and can be mounted on the left or right side of compatible devices. Siemens' current product data identifies this exact article as a lateral auxiliary switch with 2 NO contacts for 3RT2.2, 3RT2.3, 3RT2.4 and 3RH2 devices.

Siemens SIRIUS Auxiliary Contact Block

The 3RH2921-1DA20 is an accessory used to expand the auxiliary-contact functionality of compatible Siemens contactors and contactor relays.

Auxiliary contacts are commonly used to provide additional switching paths for control, feedback, signalling and interlocking without affecting the main power contacts.

Typical applications include:

• Contactor status feedback

• PLC input signals

• Electrical interlocking

• Control-circuit logic

• Machine sequencing

• Auxiliary signalling

• Motor-control circuits

• Industrial automation

2 NO Auxiliary Contacts

The 3RH2921-1DA20 provides 2 normally open (NO) auxiliary contacts.

The available contact paths are identified as:

53/54 and 63/64

These additional contacts can be used according to the control-circuit requirements.

Typical uses include:

• Contactor ON feedback

• PLC monitoring

• Auxiliary relay logic

• Interlocking

• Sequential control

• Status indication

• Machine-control functions

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

Left or Right Lateral Mounting

A key feature of the 3RH2921-1DA20 is its lateral mounting capability.

The auxiliary contact block can be mounted on the left or right side of compatible SIRIUS contactors and contactor relays. Siemens' catalog specifically lists these devices as laterally mountable auxiliary switches for right- and/or left-side installation.

This provides greater flexibility when designing compact control panels.

Compatibility with 3RT2 and 3RH2 Devices

Siemens specifies the 3RH2921-1DA20 for use with:

• 3RT2.2

• 3RT2.3

• 3RT2.4

• 3RH2 contactor relays

The current Siemens product data identifies the article as a lateral 2 NO auxiliary switch for these compatible devices.

Compatibility should be checked against the exact contactor article number before installation.

Screw-Terminal Connections

The 3RH2921-1DA20 uses screw terminals for its auxiliary-contact connections.

Screw terminals provide a familiar wiring method for panel builders and maintenance teams and are suitable for conventional industrial control-panel wiring.

Industrial Automation Applications

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

Typical applications include:

Motor Control

Auxiliary contacts can provide contactor-state feedback and interlocking signals within motor starters.

PLC Systems

The contacts can be connected to digital PLC inputs for monitoring the operating state of a contactor.

Machine Control

Additional contacts can be used for sequencing and machine-control logic.

Industrial Panels

The lateral mounting arrangement is suitable for compact electrical control-panel designs.

Automation Systems

The auxiliary contacts can provide additional control and signalling paths without modifying the main power circuit.

Suitable for OEMs and Panel Builders

The 3RH2921-1DA20 is suitable for OEM machine manufacturers, electrical panel builders, automation integrators and industrial maintenance professionals.

Its 2 NO contact configuration, lateral mounting and screw-terminal connections make it a practical accessory for expanding compatible Siemens SIRIUS contactor and contactor-relay assemblies.

Key Features

• Siemens SIRIUS auxiliary contact block

• Article number 3RH2921-1DA20

• Laterally mountable design

• Mountable on left and/or right

• 2 NO auxiliary contacts

• Contact paths: 53/54 and 63/64

• Screw terminals

• Compatible with selected 3RT2 contactors

• Compatible with 3RH2 contactor relays

• Suitable for PLC feedback

• Suitable for electrical interlocking

• Suitable for machine-control applications

• Suitable for industrial automation

Benefits

• Additional auxiliary contacts: Provides two extra NO switching paths.

• Flexible mounting: Can be installed laterally on the left or right of compatible devices.

• Compact panel design: Lateral mounting helps make efficient use of control-panel space.

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

• PLC integration: Can provide useful contactor-status signals.

• Interlocking capability: Supports control-system interlocking arrangements.

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

• Industrial suitability: Designed for Siemens SIRIUS contactor and contactor-relay systems.

Why Choose Siemens 3RH2921-1DA20?

The Siemens 3RH2921-1DA20 provides a straightforward way to expand the auxiliary switching capability of compatible Siemens 3RT2 contactors and 3RH2 contactor relays.

Its 2 NO contacts, lateral left/right mounting and screw-terminal design make it suitable for control-panel applications requiring additional feedback, signalling or interlocking contacts. Siemens specifically identifies this article for compatible 3RT2.2, 3RT2.3, 3RT2.4 and 3RH2 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 3RH2921-1DA20?

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 open (2 NO) auxiliary contacts.

3. What are the contact paths?

The specified contact paths are 53/54 and 63/64.

4. Can it be mounted on either side?

Yes. It is designed for lateral mounting on the left and/or right side of compatible devices.

5. Which Siemens 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 auxiliary contacts be used for?

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

8. Does it change the main power switching capability?

No. It provides additional auxiliary contact paths for control and signalling; the main power switching function remains with the compatible contactor.

9. Is it suitable for OEM control panels?

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

10. Where can I buy Siemens 3RH2921-1DA20 in India?

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

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