Siemens Industrial Controls 3RU2126-4DB0 Overload Relay

The Siemens 3RU2126-4DB0 is a high-performance SIRIUS thermal overload relay engineered for precise protection of three-phase motors. Designed for seamless integration, this Size S0 overload relay offers a versatile 20-25A current adjustment range, making it a critical component for safeguarding industrial pump motors, fans, and compressors. Utilizing a reliable bi-metal switching mechanism, it provides Class 10 tripping capability, ensuring circuit interruption within ten seconds during overcurrent conditions or phase failures. This unit is optimized for direct mounting to 3RT202 contactors, significantly reducing enclosure space requirements while maintaining robust electrical connectivity through heavy-duty screw terminals. Featuring integrated phase loss sensitivity and a manual/automatic reset function, the 3RU2126-4DB0 ensures continuous operational stability and rapid system recovery. Its 1NO + 1NC auxiliary contacts provide reliable fault signaling, while the physical test slide and stop button allow technicians to verify control circuit integrity without full system discharge.

• Precise Motor Protection: The thermal magnetic trip mechanism safeguards against overheating and phase asymmetry, preventing motor burnout.
• SIRIUS Modular Compatibility: Designed specifically for direct connection to Siemens S0 contactors (3RT202-series), eliminating the need for additional wiring or mounting brackets.
• Flexible Current Calibration: The rotary dial allows for fine-tuning the thermal overload setting between 20A and 25A to match specific motor nameplate data.
• Dual Reset Modes: Easily toggle between manual and automatic reset options to accommodate various safety protocols and unmanned equipment sites.
• Auxiliary Signaling: Built-in 1NO and 1NC contacts provide immediate feedback to the PLC or control system during a trip event.

Is the 3RU2126-4DB0 compatible with older 3RU11 series contactors?
Technicians upgrading from the legacy 3RU1126 series should note that the 3RU2126-4DB0 is designed for the 3RT2 series contactors. If used with older 3RU11 contactors, a separate stand-alone mounting bracket is required, or the contactor should be upgraded to a 3RT2 model for direct mounting.

What does the Class 10 rating signify in industrial applications?
Class 10 indicates that the relay will trip within 10 seconds or less at 600% of the set current. This is standard for most industrial motors with normal startup durations, ensuring the thermal limit of the motor windings is not exceeded.

Can I test the control circuit without an actual overload event?
Yes, the unit features a dedicated TEST slide and STOP button. This allows maintenance crews to manually simulate a trip to verify that the auxiliary contacts are correctly opening or closing the control circuit without forcing an overcurrent state.

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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.