Overview
The Siemens 3RH1921-1FA31 is a front-mounted auxiliary switch block designed for expanding the control circuit capabilities of SIRIUS 3RT1 power contactors and 3RH1 contactor relays. With 3 normally open (NO) and 1 normally closed (NC) instantaneous contacts, this 4-pole mounting block conforms to DIN EN 50005 and IEC 60947-5-1 standards. The snap-on design enables tool-free installation and removal on contactor sizes S0 through S12, making it ideal for field technicians and system integrators who need rapid configuration changes.
Key Features
- Contact Configuration: 3 NO + 1 NC instantaneous contacts in a compact 4-pole design
- Quick Installation: Snap-on front-mount mechanism with no tools required; removable for easy reconfiguration
- Screw Terminals: Reliable screw-type connections for secure wiring; cage clamp variants available
- Wide Voltage Range: AC and DC operation from 24 V to 690 V, supporting multiple utilization categories (AC-12, AC-14, AC-15, DC-12, DC-13)
- Modular Design: Part of the SIRIUS modular system; can be combined with side-mounted auxiliary blocks for up to 6 additional poles
- Compact Footprint: Minimal mounting space on contactor allows for dense control panel layouts
Technical Specifications
The 3RH1921-1FA31 meets stringent industrial standards and delivers reliable performance across diverse switching scenarios:
- AC-12 Rating: 10 A at 24 V or 230 V; 10 A maximum
- AC-14 Rating: 6 A at 125 V or 250 V
- AC-15 Rating: 6 A at 24 V or 230 V; 3 A at 400 V; 1 A at 690 V
- DC-12 Rating (2-current-path): 10 A at 24 V or 60 V; 4 A at 110 V
- DC-13 Rating: 6 A at 24 V; 2 A at 60 V; 1 A at 110 V; 0.3 A at 220 V
- Contact Type: Instantaneous (non-delayed) switching
- Terminal Style: Screw-type connections
- Mounting: DIN EN 50005 compliant snap-on front mount
- Operating Temperature: Suitable for all climate conditions per IEC 60947
- Applicable Standards: IEC 60947-5-1, EN 50005, VDE 0660, UL 508
Typical Applications
The Siemens 3RH1921-1FA31 is commonly used in:
- Machine tool control circuits requiring extended auxiliary contacts for interlocking and feedback signals
- HVAC and refrigeration compressor starter systems where multiple status indicators and safety interlocks must be monitored
- Pump and motor control panels that need additional NO/NC switch combinations without adding a separate relay module
- Manufacturing automation systems requiring modular expansion of control logic without rewiring the main contactor
- Building automation and process control installations where panel space is limited and quick replacement is necessary
Compatibility & Replacements
Compatible With
- Siemens 3RT1 power contactors (sizes S0, S2, S3, S4–S12)
- Siemens 3RH1 contactor relays
- SIRIUS modular contactor systems
- Control circuits operating at 24 V AC/DC up to 690 V AC
- DIN EN 50005 standard mounting rails and enclosures
Replaces / Drop-In Replacement For
- Earlier versions of the 3RH1921 series auxiliary blocks
- Note: Verify specific model interchangeability with Siemens documentation or your system integrator, as some variants (e.g., 2NO+2NC configurations) may require different contact arrangements
Works With
- Siemens SIRIUS 3RH19 and 3RH29 auxiliary switch block systems
- Front-mount and lateral-mount configurations within the 3RH19/3RH29 family
- Side-mounted auxiliary blocks for expanded pole configurations
- IEC 60947-compliant control circuits and panel builders’ software (TIA Portal for configuration planning)
- Screw-terminal and cage-clamp connection variants across the 3RT1/3RH1 range
