The Siemens 3RU2126-4NB00-8K is a high-performance thermal overload relay from the trusted SIRIUS 3RU2 Series, designed to provide reliable protection for three-phase motors against overload conditions, phase failure, and prolonged overcurrent operation. Engineered for industrial motor control applications, this relay features an adjustable current setting range of 24–30 A, Class 10 tripping characteristics, and compatibility with Size S0 Siemens contactors, making it ideal for compact motor starter assemblies and automation systems. The 3RU2126 family is designed specifically for direct contactor mounting and dependable motor protection.
The relay operates using Siemens' proven thermal overload protection technology, continuously monitoring motor current and disconnecting the motor when overload conditions persist. Its inverse-time delayed tripping characteristic helps prevent motor overheating, insulation damage, and premature motor failure while allowing normal motor starting currents. The relay also provides phase-failure sensitivity for enhanced motor safety and operational reliability.
The Variant NB008K offers an adjustable overload release setting of 24–30 A, making it suitable for protecting motors used in pumps, compressors, conveyor systems, fans, HVAC equipment, machine tools, packaging machinery, and industrial automation installations. Its compact S0 frame size enables efficient integration into motor control panels and starter combinations. Based on Siemens' SIRIUS 3RU2 sizing structure, the NB variant is positioned below the 30–36 A PB variant within the Size S0 range.
As part of the Siemens SIRIUS motor protection portfolio, the 3RU2126-4NB00-8K supports both manual and automatic reset modes, providing flexibility for different operating requirements and maintenance procedures. The relay is designed with screw-type terminals for secure wiring and reliable electrical connections in demanding industrial environments.
Manufactured to Siemens' stringent quality standards, the 3RU2126-4NB00-8K delivers dependable long-term performance in manufacturing facilities, water treatment plants, process industries, material handling systems, and infrastructure projects.
| Specification | Details |
|---|---|
| Product Name | Thermal Overload Relay |
| Part Number | 3RU2126-4NB00-8K |
| SKU | 3RU2126-4NB00-8K |
| Brand | Siemens |
| Product Family | SIRIUS 3RU2 |
| Product Type | Motor Protection Relay |
| Variant | NB008K |
| Current Setting Range | 24–30 A |
| Relay Size | S0 |
| Trip Class | Class 10 |
| Operating Principle | Thermal |
| Mounting Type | Direct Contactor Mounting |
| Main Circuit Connection | Screw Terminal |
| Auxiliary Circuit Connection | Screw Terminal |
| Reset Type | Manual / Automatic |
| Number of Poles | 3 |
| Protection Features | Overload & Phase Failure Protection |
| Application | Industrial Motor Protection |
| Manufacturer | Siemens |
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