The Siemens 3RU2146-4LB00-8K is a robust thermal overload relay from the trusted SIRIUS 3RU2 Series, designed to provide dependable protection for three-phase motors against overload conditions, phase failure, and excessive current draw. Engineered for demanding industrial applications, this relay features an adjustable current setting range of 70–90 A, Class 10 tripping characteristics, and compatibility with Size S3 contactors.
The relay operates using Siemens' proven thermal overload protection technology, continuously monitoring motor current and disconnecting the motor when overload conditions persist. This helps prevent motor overheating, insulation damage, reduced equipment life, and costly downtime while improving operational reliability.
The Variant LB008K is designed for contactor mounting and incorporates a thermal inverse-time delayed overload release with an adjustable setting range of 70–90 A. Its Class 10 trip characteristic provides fast and effective protection for standard motor starting applications while minimizing nuisance tripping during normal operation.
As part of the Siemens SIRIUS motor protection portfolio, the 3RU2146-4LB00-8K supports both manual and automatic reset modes, allowing users to configure protection according to plant operating requirements and safety procedures. The relay also includes integrated 1 NO + 1 NC auxiliary contacts for trip indication and control circuit integration.
The device is designed with screw-type terminals for both the main and auxiliary circuits, ensuring secure electrical connections and simplified installation. Its compact S3 frame size allows seamless integration into motor starter assemblies, MCC panels, and industrial control systems.
In addition to overload protection, the relay provides phase-failure sensitivity, helping protect motors from damaging single-phasing conditions. This makes it ideal for pumps, compressors, conveyors, HVAC systems, manufacturing equipment, water treatment plants, and process automation installations.
Manufactured according to Siemens' stringent quality standards, the 3RU2146-4LB00-8K delivers reliable long-term performance in demanding industrial environments where dependable motor protection is essential.
| Specification | Details |
|---|---|
| Product Name | Thermal Overload Relay |
| Part Number | 3RU2146-4LB00-8K |
| SKU | 3RU2146-4LB00-8K |
| Brand | Siemens |
| Product Family | SIRIUS 3RU2 |
| Product Type | Motor Protection Relay |
| Variant | LB008K |
| Current Setting Range | 70–90 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 Operational Power @ 400V AC-3 | 45 kW |
| Rated Operational Power @ 500V AC-3 | 55 kW |
| Rated Operational Power @ 690V AC-3 | 75 kW |
| Number of Main Poles | 3 |
| Protection Features | Overload & Phase Failure Protection |
| Protection Class | IP20 |
| Application | Industrial Motor Protection |
| Manufacturer | Siemens |
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