Siemens Industrial Controls 3RH2921-2DE11 Auxiliary Switch

The Siemens 3RH2921-2DE11 is a high-performance auxiliary switch block designed for seamless integration with SIRIUS 3RT2 contactors and 3RH2 contactor relays. This front-mounting module features a 1NO + 1NC (1 Normally Open / 1 Normally Closed) contact configuration, engineered specifically for electronic-compatible signaling in demanding industrial environments. As a direct replacement for the legacy 3RH1921-2DE11, it maintains a compact form factor while offering enhanced contact reliability for low-level signals. The spring-loaded terminals ensure vibration-proof connections, reducing maintenance overhead in high-cycle HVACR motor control applications. This Siemens auxiliary contact is rated for Size S00 to S3 frames, providing versatile logic feedback for automation circuits. Its high contact reliability makes it ideal for interfacing with PLC inputs where signal integrity is critical. When retrofitting older systems, this component ensures full mechanical compatibility without requiring panel redesign.

• Direct Replacement: Fully replaces the 3RH1921-2DE11 with identical mounting footprints for fast field swaps.
• Spring-Loaded Connection: Utilizes cage clamp technology to eliminate torque-related failures and ensure permanent contact pressure.
• Electronic Compatibility: Optimized for low-current switching, making it reliable for modern digital control systems and PLCs.
• Space-Efficient Design: Front-mounting configuration allows for expanded I/O without increasing the lateral footprint of the SIRIUS contactor.

Can I use the 3RH2921-2DE11 on older 3RT1 series contactors?
No, this module is specifically engineered for the 3RT2 series (SIRIUS Innovation). For 3RT1 series contactors, you must utilize the 3RH19 series components.

What is the primary advantage of the 1NO/1NC configuration in HVACR?
This setup allows for simultaneous status signaling (NO) and electrical interlocking (NC) to prevent short circuits or to provide "run/fault" status feedback to a head-end controller.

Are the spring terminals better than screw terminals for rooftop units?
Yes, spring-loaded terminals are preferred in high-vibration environments like RTUs or compressors as they prevent wires from backing out over time, unlike traditional screw terminals.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.