The Siemens 3RU2136-4RB00-8K 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 excessive current draw. This motor protection relay features an adjustable current setting range of 70–80 A, Class 10 tripping characteristics, and is designed for use with Size S2 SIRIUS contactors in industrial motor control applications.
The relay operates using Siemens' proven thermal overload protection principle, 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. Siemens 3RU2 overload relays are specifically engineered for current-dependent motor protection and phase-loss detection.
The Variant RB008K incorporates a thermal inverse-time delayed overload release with an adjustable setting range of 70–80 A. It is designed for contactor mounting on compatible Siemens SIRIUS Size S2 contactors and 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 3RU2136-4RB00-8K 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.
Its compact S2 frame size allows seamless integration into motor starter assemblies, MCC panels, and industrial control systems. The relay utilizes screw-type terminals for secure electrical connections and easy installation in industrial environments.
Featuring a Class 10 trip characteristic, the relay provides rapid protection for standard motor starting applications while minimizing nuisance tripping during normal operation. It also incorporates phase-failure protection, helping safeguard motors against damaging single-phasing conditions.
Manufactured according to Siemens' stringent quality standards, the 3RU2136-4RB00-8K delivers reliable long-term performance in manufacturing facilities, water treatment plants, process industries, material handling systems, HVAC installations, and industrial automation projects.
| Specification | Details |
|---|---|
| Product Name | Thermal Overload Relay |
| Part Number | 3RU2136-4RB00-8K |
| SKU | 3RU2136-4RB00-8K |
| Brand | Siemens |
| Product Family | SIRIUS 3RU2 |
| Product Type | Motor Protection Relay |
| Variant | RB008K |
| Current Setting Range | 70–80 A |
| Relay Size | S2 |
| Trip Class | Class 10 |
| Operating Principle | Thermal |
| Mounting Type | Contactor Mounting |
| Main Circuit Connection | Screw Terminal |
| Auxiliary Contacts | 1 NO + 1 NC |
| Reset Type | Manual / Automatic |
| Protection Features | Overload & Phase Failure Protection |
| Application | Industrial Motor Protection |
| Manufacturer | Siemens |
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