The Siemens 3RU2126-4BB0 is a high-performance thermal overload relay from the trusted SIRIUS 3RU2 Series, engineered to provide reliable protection for three-phase motors against overload conditions, phase failure, and prolonged overcurrent operation. Featuring an adjustable current setting range of 14–20 A, Class 10 tripping characteristics, and compatibility with Size S0 Siemens contactors, this relay is ideal for industrial motor control and protection applications.
Designed for direct contactor mounting, the relay continuously monitors motor current and responds to overload conditions using Siemens' proven inverse-time thermal tripping technology. This protection mechanism helps prevent motor overheating, insulation damage, and costly downtime while allowing normal motor starting currents.
The Variant BB0 offers an adjustable overload release setting of 14–20 A, making it suitable for protecting motors used in pumps, compressors, conveyor systems, fans, HVAC equipment, packaging machinery, machine tools, and industrial automation systems. Its compact S0 frame size enables easy integration into motor starter assemblies, MCC panels, switchboards, and control panels.
The relay includes 1 Normally Open (NO) and 1 Normally Closed (NC) auxiliary contact for status indication, alarm signaling, and control circuit integration. It supports both manual and automatic reset modes, providing flexibility based on application requirements and operating procedures.
Built with robust industrial-grade materials and screw-type terminal connections, the 3RU2126-4BB0 ensures secure wiring, simplified installation, and long service life in demanding industrial environments. As part of Siemens' globally recognized SIRIUS motor protection portfolio, it delivers dependable performance and reliable motor protection.
| Specification | Details |
|---|---|
| Product Name | Thermal Overload Relay |
| Part Number | 3RU2126-4BB0 |
| SKU | 3RU2126-4BB0 |
| Brand | Siemens |
| Product Family | SIRIUS 3RU2 |
| Product Type | Motor Protection Relay |
| Variant | BB0 |
| Current Setting Range | 14–20 A |
| Relay Size | S0 |
| Trip Class | Class 10 |
| Operating Principle | Thermal |
| Mounting Type | Direct Contactor Mounting |
| Main Circuit Connection | Screw Terminal |
| Auxiliary Contacts | 1 NO + 1 NC |
| Reset Type | Manual / Automatic |
| Number of Poles | 3 |
| Protection Features | Overload & Phase Failure Protection |
| Application | Industrial Motor Protection |
| Manufacturer | Siemens |
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