The Siemens 3RU2126-4BB00-8K is a reliable thermal overload relay from the renowned SIRIUS 3RU2 Series, designed to provide dependable protection for three-phase motors against overload conditions, phase failure, and excessive current draw. The relay features an adjustable current setting range of 14–20 A, Class 10 tripping characteristics, and is designed for direct mounting on Siemens Size S0 contactors, making it ideal for industrial motor control and automation applications. The corresponding BB0 variant in the same series is rated for 14–20 A and Size S0 contactor mounting.
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. Phase-failure sensitivity further enhances motor protection and operational reliability. Siemens SIRIUS 3RU2 relays are designed specifically for motor protection in industrial applications.
The Variant BB008K 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, machine tools, packaging machinery, and industrial automation installations. Its compact S0 frame size enables efficient integration into motor starter assemblies and control panels.
As part of the Siemens SIRIUS motor protection portfolio, the 3RU2126-4BB00-8K supports both manual and automatic reset modes and incorporates auxiliary contacts for signaling, monitoring, and control circuit integration. The relay is designed with screw-type terminals to ensure secure electrical connections and simplified installation.
Manufactured to Siemens' stringent quality standards, the 3RU2126-4BB00-8K delivers dependable long-term performance in demanding industrial environments including manufacturing facilities, water treatment plants, process industries, and material handling systems.
| Specification | Details |
|---|---|
| Product Name | Thermal Overload Relay |
| Part Number | 3RU2126-4BB00-8K |
| SKU | 3RU2126-4BB00-8K |
| Brand | Siemens |
| Product Family | SIRIUS 3RU2 |
| Product Type | Motor Protection Relay |
| Variant | BB008K |
| 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 Circuit Connection | Screw Terminal |
| 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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