The Siemens 3RU2136-4QB00-8K is a premium thermal overload relay from the trusted SIRIUS 3RU2 Series, engineered to provide reliable protection for three-phase motors against overload conditions, phase failure, and excessive current draw. Designed for industrial motor control applications, this relay features an adjustable current setting range of 63–70 A, Class 10 tripping characteristics, and compatibility with Size S2 contactors. The relay is ideal for protecting motors used in manufacturing plants, process industries, pumping systems, compressors, conveyors, and automation equipment. Based on the Siemens 3RU2 S2-series product family, the QB variant falls between the commonly available 57–63 A and 70–80 A models.
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, premature motor failure, and costly production downtime. The inverse-time delayed tripping characteristic ensures dependable protection while allowing normal motor starting currents. Siemens SIRIUS overload relays are also designed with phase-failure sensitivity for enhanced motor safety.
The Variant QB008K is designed for contactor mounting and incorporates a thermal inverse-time delayed overload release with an adjustable current setting range of 63–70 A. It is intended for direct installation on compatible Siemens S2 contactors, enabling compact and efficient motor starter assemblies. Similar S2-frame variants in the 3RU2136 family share the same mounting concept, Class 10 protection, and motor protection functionality.
As part of the Siemens SIRIUS motor protection portfolio, the 3RU2136-4QB00-8K supports both manual and automatic reset modes, allowing users to configure protection according to operational requirements and plant safety procedures. Integrated auxiliary contacts enable easy incorporation into control circuits for status monitoring and fault signaling.
The compact S2 design allows seamless integration into motor control centers (MCCs), switchboards, industrial control panels, and OEM machinery. Manufactured to Siemens' stringent quality standards, the relay delivers dependable long-term performance in demanding industrial environments.
| Specification | Details |
|---|---|
| Product Name | Thermal Overload Relay |
| Part Number | 3RU2136-4QB00-8K |
| SKU | 3RU2136-4QB00-8K |
| Brand | Siemens |
| Product Family | SIRIUS 3RU2 |
| Product Type | Motor Protection Relay |
| Variant | QB008K |
| Current Setting Range | 63–70 A |
| Relay Size | S2 |
| 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 |
| Rated Insulation Voltage | 1000 V |
| Number of Main Poles | 3 |
| Protection Features | Overload & Phase Failure Protection |
| Application | Industrial Motor Protection |
| Manufacturer | Siemens |
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