The Siemens 3RU2146-4JB00-8K is a high-quality thermal overload relay from the trusted SIRIUS 3RU2 Series, designed to provide reliable motor protection against overload conditions, phase failure, and excessive current draw. This relay features an adjustable current setting range of 45–63 A, Class 10 tripping characteristics, and is designed for use with Size S3 contactors in industrial motor control applications.
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 overheating, insulation damage, reduced motor life, and costly downtime while improving operational reliability. SIRIUS thermal overload relays are specifically engineered for current-dependent motor protection and phase-failure detection.
The Variant JB008K is designed for contactor mounting and incorporates a thermal inverse-time delayed overload release with an adjustable setting range of 45–63 A. It is ideal for protecting motors used in pumps, compressors, conveyors, fans, HVAC systems, manufacturing machinery, and process automation equipment.
As part of the Siemens SIRIUS motor protection portfolio, the 3RU2146-4JB00-8K supports both manual and automatic reset modes, allowing users to configure protection according to operational requirements and plant safety procedures. The relay also includes integrated 1 NO + 1 NC auxiliary contacts for trip indication and control circuit integration. Similar S3-series models share these design characteristics within the 3RU2146 family.
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.
Featuring a Class 10 trip characteristic, the relay provides rapid protection for standard motor starting applications while minimizing nuisance tripping during normal operation. In addition, the relay offers phase-failure sensitivity, helping protect motors from damaging single-phasing conditions.
Manufactured according to Siemens' stringent quality standards, the 3RU2146-4JB00-8K delivers dependable long-term performance in demanding industrial environments and is widely used across manufacturing facilities, water treatment plants, process industries, material handling systems, and infrastructure projects.
| Specification | Details |
|---|---|
| Product Name | Thermal Overload Relay |
| Part Number | 3RU2146-4JB00-8K |
| SKU | 3RU2146-4JB00-8K |
| Brand | Siemens |
| Product Family | SIRIUS 3RU2 |
| Product Type | Motor Protection Relay |
| Variant | JB008K |
| Current Setting Range | 45–63 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 |
| Number of Main Poles | 3 |
| Protection Features | Overload & Phase Failure Protection |
| Application | Industrial Motor Protection |
| Manufacturer | Siemens |
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