The Siemens 3RH1921-1EA20 is a first laterally mountable auxiliary contact block from the Siemens SIRIUS accessory range, designed for compatible 3RT1 contactors in sizes S6 to S12. It provides 2 normally open (2 NO) instantaneous auxiliary contacts and uses screw-terminal connections. Siemens' current product data identifies the article as a first lateral auxiliary switch for 3RT1 contactors.
This accessory is used to add additional auxiliary switching paths for contactor feedback, signalling, interlocking and control applications without changing the main power-switching function of the connected contactor.
The 3RH1921-1EA20 is designed for use with large Siemens SIRIUS contactors where additional auxiliary contacts are required.
Auxiliary contacts can provide separate control and feedback signals while the main contactor continues to handle the primary load.
Typical applications include:
Contactor status feedback
PLC input signals
Electrical interlocking
Control-circuit logic
Machine sequencing
Auxiliary signalling
Motor-control circuits
Industrial automation
The 3RH1921-1EA20 provides 2 normally open (NO) instantaneous auxiliary contacts. Siemens' current datasheet identifies two instantaneous contacts and no changeover contacts.
These contacts can be used for:
Contactor ON feedback
PLC monitoring
Auxiliary signalling
Relay logic
Machine sequencing
Control-system feedback
Interlocking circuits
When the associated contactor operates, the NO auxiliary contacts change state to provide the required control or feedback signal.
A key feature of the 3RH1921-1EA20 is its first lateral mounting position.
It is designed to mount laterally on compatible SIRIUS contactors and is part of the first lateral auxiliary-switch family for S6 to S12 contactors. Siemens' catalog identifies the compatible 3RT1 range as 3RT1.5 through 3RT1.7.
The accessory can be used where auxiliary contacts need to be added to the side of a large-frame contactor assembly.
The 3RH1921-1EA20 is intended for compatible Siemens 3RT1 contactors in S6 to S12 sizes, including the applicable 3RT1.5 to 3RT1.7 range.
This makes it suitable for large industrial motor-control assemblies and high-power contactor applications.
Typical applications include:
Large motor starters
Heavy-duty machinery
Industrial conveyors
Pumps
Compressors
Large fans
Production lines
Industrial automation panels
The exact compatibility should always be checked against the complete contactor article number before installation.
The 3RH1921-1EA20 uses screw terminals for the auxiliary circuit connections. Siemens' current product data identifies it as a screw-terminal auxiliary switch.
This provides a conventional connection method familiar to industrial panel builders and maintenance teams.
The associated auxiliary circuits should always be wired according to the manufacturer's instructions and applicable electrical ratings.
Both contacts in the 3RH1921-1EA20 are instantaneous NO contacts.
The auxiliary contacts operate with the associated contactor rather than incorporating an independent time-delay function.
This makes the accessory suitable for immediate status feedback, signalling and control functions.
The 3RH1921-1EA20 can expand the auxiliary control functionality of compatible large-frame SIRIUS contactors.
The two NO contacts can provide contactor status information or additional motor-control signals.
The auxiliary contacts can be connected to suitable PLC digital inputs for monitoring the operating state of the contactor.
The contacts can support machine sequencing, signalling and control logic.
The lateral mounting arrangement provides an organized way to add auxiliary switching capability to large contactors.
The additional contact paths can provide feedback and control signals within automated industrial equipment.
The 3RH1921-1EA20 is suitable for OEM machine manufacturers, electrical panel builders, automation integrators and industrial maintenance professionals working with large SIRIUS contactors.
Its 2 NO configuration, first lateral mounting position, S6–S12 compatibility and screw-terminal connections make it suitable for applications requiring additional auxiliary control functionality.
Siemens SIRIUS auxiliary contact block
Article number 3RH1921-1EA20
First laterally mountable auxiliary switch
2 NO auxiliary contacts
Instantaneous contacts
2-pole configuration
Screw terminals
Suitable for S6 to S12 contactor sizes
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
2 NO contacts: Provides two additional normally open switching paths.
First lateral mounting: Adds auxiliary functionality to the side of compatible large-frame contactors.
S6–S12 compatibility: Suitable for large Siemens SIRIUS contactor assemblies.
Screw terminals: Provides a familiar industrial wiring method.
Instantaneous operation: Auxiliary contacts follow the operating state of the associated contactor.
PLC integration: Supports contactor-status monitoring.
Interlocking support: Can be incorporated into suitable auxiliary control circuits.
Compact lateral arrangement: Adds auxiliary functions without requiring a separate external relay.
The Siemens 3RH1921-1EA20 provides a practical solution for adding two instantaneous normally open auxiliary contacts to compatible Siemens SIRIUS contactors.
As the first laterally mountable auxiliary contact block, it is particularly useful for S6 to S12 contactors where additional feedback, signalling or control contacts are required. Siemens' current product information identifies the article as an active product and specifies it as a 2 NO screw-terminal first lateral auxiliary switch for 3RT1 contactors.
For OEMs, panel builders and automation integrators, it provides an effective way to expand auxiliary contact functionality while keeping the main contactor assembly intact.
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
It is a Siemens SIRIUS first laterally mountable auxiliary contact block with 2 normally open contacts for compatible 3RT1 contactors.
It provides 2 NO instantaneous auxiliary contacts.
It identifies the auxiliary switch as the first laterally mountable auxiliary-contact block in the applicable SIRIUS contactor arrangement.
It is designed for compatible Siemens 3RT1 contactors in S6 to S12 sizes, including the relevant 3RT1.5 to 3RT1.7 range.
Yes. The product uses screw-terminal connections.
Yes. Both auxiliary contacts are instantaneous NO contacts.
They can be used for PLC feedback, signalling, control logic, contactor monitoring and machine sequencing.
No. It is an auxiliary contact block; the main load is switched by the compatible contactor.
Yes. It is designed for compatible S6 to S12 SIRIUS contactors, making it suitable for large industrial switching assemblies.
You can explore the Siemens product range at SB Smart for Siemens auxiliary contact blocks, contactors and other industrial automation products.
| Specification | Details |
|---|---|
| Product Name | Auxiliary Contact Block |
| Manufacturer | Siemens |
| Series | SIRIUS |
| Order Code | 3RH1921-1EA20 |
| Product Type | Auxiliary Contact Block |
| Contact Configuration | 2 NO |
| Number of Poles | 2 Pole |
| Mounting Position | First Laterally Mountable |
| Compatible Contactor Sizes | S6 to S12 |
| Terminal Type | Screw Terminals |
| Mounting Method | Side Mount |
| Electrical Function | Signaling & Monitoring |
| Suitable For | Siemens SIRIUS Contactors |
| Industrial Application | Yes |
| Mechanical Life | Long Service Life |
| Electrical Durability | Industrial Grade |
| Brand | Siemens |
| Condition | New & Genuine Product |
No reviews yet.