Siemens 3RU2116-0KB0 Overload Relay 0.90–1.25 A, Thermal Motor Protection S00, Class 10 Original Brand New

Overview

The Siemens 3RU2116-0KB0 is a cornerstone of the SIRIUS modular system, specifically engineered to provide robust protection for three-phase motors against excessive temperature rises due to overloads or phase failures. As part of the 3RU21 generation, this thermal overload relay is optimized for use with SIRIUS 3RT contactors, creating a compact and efficient motor starter combination.

Built for durability and precision, the 3RU2116-0KB0 monitors the current flowing through the motor via integrated bimetal strips. If the current exceeds the set value (0.90 – 1.25 A) for a specific duration, the bimetal strips heat up and trigger the auxiliary contacts, safely disconnecting the motor from the power supply via the contactor. Its Size S00 form factor ensures it occupies minimal space in the control cabinet while delivering maximum industrial-grade protection.

Key Benefit

• Enhanced Motor Longevity: By preventing overheating caused by overcurrent or phase imbalance, it significantly extends the operational lifespan of your motors.

• Space-Saving Design: The compact S00 size allows for high-density mounting in electrical panels, reducing overall cabinet footprints.

• Global Standards Compliance: Fully certified for international use (IEC, UL, CSA), making it suitable for global export and diverse industrial environments.

• Ease of Integration: Designed for direct mounting onto 3RT20 contactors, eliminating the need for additional wiring between the contactor and the relay.

• Operational Flexibility: The dual Manual and Automatic reset capability provides operators with control over system recovery based on specific safety protocols.

Functions and Features

1. Thermal Overload Protection

The relay utilizes a bimetallic release mechanism that provides a delayed response to overcurrent. The tripping characteristic follows Class 10, ensuring the motor is protected during standard starting cycles.

2. Phase Failure Sensitivity

In the event of a phase failure, the 3RU2116-0KB0 reacts faster than during a symmetrical overload, providing critical protection against the rapid heating associated with single-phasing.

3. Manual/Auto Reset and Stop Function

Users can choose between manual reset (requiring physical intervention) or automatic reset (allowing the system to restart after cooling). A dedicated “Stop” button can be used to manually open the NC contact without tripping the relay.

4. Integrated Auxiliary Contacts

Equipped with 1 NO (Normally Open) and 1 NC (Normally Closed) auxiliary contact. These are essential for signaling faults to a PLC or triggering an alarm light.

Application

The Siemens 3RU2116-0KB0 is ideal for a wide range of industrial and commercial applications where small motor protection is required:

• Conveyor Systems: Protecting small motors in material handling and packaging lines.

• Pumps and Fans: Ensuring reliable operation of HVAC systems and fluid transport.

• Machine Tooling: Guarding precision motors in CNC and milling machines.

• General Automation: Any application involving 3-phase AC motors within the 0.90 to 1.25 Amp range.

Installation and Maintenance

Thanks to the SIRIUS modular system, installation is straightforward. The relay plugs directly into the load-side terminals of a Size S00 contactor. The screw terminals are designed for high-vibration environments, ensuring a “gas-tight” connection that prevents arcing. Maintenance is minimal; however, it is recommended to periodically test the tripping mechanism using the integrated “Test” slide to ensure mechanical readiness.

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