The Siemens 3RU2146-4FB00-8K is a high-quality thermal overload relay from the trusted SIRIUS 3RU2 Series, designed to provide reliable protection for three-phase motors against overload conditions, phase failure, and excessive current draw. The relay features an adjustable current setting range of 28–40 A, Class 10 tripping characteristics, and compatibility with Size S3 contactors, making it ideal for industrial motor protection applications.
The relay operates using Siemens' proven thermal overload protection principle, continuously monitoring motor current and disconnecting the motor when overload conditions persist. This helps prevent overheating, insulation damage, reduced motor life, and costly downtime while improving operational reliability. The device is specifically designed for motor protection in demanding industrial environments.
The Variant FB008K incorporates a thermal inverse-time delayed overload release with an adjustable setting range of 28–40 A. It is designed for contactor mounting and can be combined with Siemens S3 contactors, making it suitable for motors used in pumps, compressors, conveyors, HVAC systems, fans, manufacturing equipment, and process automation applications.
As part of the Siemens SIRIUS motor protection portfolio, the 3RU2146-4FB00-8K supports both manual and automatic reset modes, allowing users to configure protection according to operational requirements and safety procedures. The relay includes integrated 1 NO + 1 NC auxiliary contacts for trip indication and control circuit integration.
The device features screw-type terminals for both the main and auxiliary circuits, ensuring secure electrical connections and simplified installation. Its compact S3 frame size enables seamless integration into motor starter assemblies, MCC panels, and industrial control systems.
Featuring a Class 10 trip characteristic, the relay provides rapid protection for standard motor starting applications while minimizing nuisance tripping during normal operation. It also incorporates phase-failure sensitivity, helping protect motors from damaging single-phasing conditions.
Manufactured according to Siemens' stringent quality standards, the 3RU2146-4FB00-8K delivers dependable long-term performance across manufacturing facilities, water treatment plants, material handling systems, process industries, and industrial automation installations.
| Specification | Details |
|---|---|
| Product Name | Thermal Overload Relay |
| Part Number | 3RU2146-4FB00-8K |
| SKU | 3RU2146-4FB00-8K |
| Brand | Siemens |
| Product Family | SIRIUS 3RU2 |
| Product Type | Motor Protection Relay |
| Variant | FB008K |
| Current Setting Range | 28–40 A |
| Relay Size | S3 |
| Trip Class | Class 10 |
| Operating Principle | Thermal |
| Mounting Type | Contactor Mounting |
| Main Circuit Connection | Screw Terminal |
| Auxiliary Circuit Connection | Screw Terminal |
| Auxiliary Contacts | 1 NO + 1 NC |
| Reset Type | Manual / Automatic |
| Rated Operating Voltage | Up to 690 V AC |
| Number of Main Poles | 3 |
| Protection Features | Overload & Phase Failure Protection |
| Protection Class | IP20 (Front) |
| Application | Industrial Motor Protection |
| Manufacturer | Siemens |
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