Siemens 3RH1921-1EA02 Auxiliary Switch Block, 2 NC Contacts

The Siemens 3RH1921-1EA02 is a high-quality auxiliary switch block designed to expand the functionality of SIRIUS 3RT1 contactors. Featuring 2 normally closed (NC) contacts, this modular component is engineered for reliable feedback and control signaling within industrial automation systems. It provides precise switching operations and is constructed to withstand the rigors of demanding electrical environments, ensuring consistent performance in control circuits.

Advantages

This auxiliary switch block offers seamless integration with 3RT1 contactors ranging from size S0 to S12. The design allows for tool-free lateral mounting, which significantly simplifies installation and maintenance processes. As part of the SIRIUS modular system, it ensures high compatibility and efficiency. The unit features positively driven contacts, which are essential for safety-critical applications, providing reliable status monitoring for power contactors.

Suitable for

• Industrial automation control circuits
• Status feedback for power contactors
• Safety-related switching applications
• Expansion of existing contactor configurations

When it may not be suitable

This specific model is designed for lateral mounting and may not be suitable for applications requiring front-mounted auxiliary switches. It is exclusively compatible with 3RT1 contactors and cannot be used with contactor series that do not support this specific modular interface.

Key specifications

• Contact configuration: 2 normally closed (NC) contacts
• Mounting type: Lateral
• Terminal type: Screw terminal
• Compatibility: SIRIUS 3RT1 contactors (sizes S0 to S12)
• Function: Instantaneous switching

How to use

The auxiliary switch block is designed for quick and easy installation. It can be attached to the side of a compatible 3RT1 contactor without the need for specialized tools. Once snapped into place, the screw terminals allow for secure connection of control wiring. Ensure the power is disconnected before installation and verify that the contactor size is within the supported S0 to S12 range to ensure proper mechanical and electrical alignment.

What to consider before purchase

• Verify the mounting orientation requirements of your current control panel layout.
• Confirm that your contactor model is part of the 3RT1 series.
• Ensure that the 2 NC contact configuration meets your specific control logic requirements.
• Check if your wiring setup is compatible with screw-type terminals.

Usage recommendations

Always ensure that the auxiliary switch is fully engaged with the contactor housing before applying power. Regularly inspect the screw terminal connections to maintain optimal electrical contact and prevent signal loss in the control circuit.