The Siemens 3RU2126-1JB00-8K is a high-quality thermal overload relay from the renowned SIRIUS 3RU2 Series, engineered to provide reliable protection for three-phase motors against overload conditions, phase failure, and prolonged overcurrent operation. Designed for industrial motor control applications, this relay features an adjustable current setting range of 4–5.5 A, Class 10 tripping characteristics, and compatibility with Size S0 Siemens contactors, making it ideal for compact motor starter assemblies and automation systems. The SIRIUS 3RU2 series is specifically developed for dependable motor protection through inverse-time delayed overload tripping.
The relay continuously monitors motor current and disconnects the motor when overload conditions persist beyond permissible limits. Its thermal overload protection mechanism helps prevent motor overheating, insulation damage, and unexpected downtime while allowing normal motor starting currents. Integrated phase-failure sensitivity further enhances operational reliability and motor safety.
The Variant JB008K offers an adjustable overload release setting of 4–5.5 A, making it suitable for protecting small industrial motors used in pumps, fans, conveyors, HVAC equipment, packaging machinery, compressors, and general automation systems. Its compact S0 frame size allows efficient integration into motor control centers, starter combinations, and OEM control panels. Based on Siemens S0-series overload relay progression, the JB008K variant is positioned between lower-current and higher-current motor protection ranges within the 3RU2126 family.
As part of the Siemens SIRIUS motor protection portfolio, the 3RU2126-1JB00-8K supports both manual and automatic reset modes and incorporates 1 Normally Open (NO) and 1 Normally Closed (NC) auxiliary contacts for signaling, monitoring, and control circuit integration. Screw-type terminals ensure secure electrical connections and simplified installation.
| Specification | Details |
|---|---|
| Product Name | Thermal Overload Relay |
| Part Number | 3RU2126-1JB00-8K |
| SKU | 3RU2126-1JB00-8K |
| Brand | Siemens |
| Product Family | SIRIUS 3RU2 |
| Product Type | Motor Protection Relay |
| Variant | JB008K |
| Current Setting Range | 4–5.5 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 |
| Rated Operational Voltage | Up to 690 V AC |
| Operating Frequency | 50/60 Hz |
| Number of Main Poles | 3 |
| Protection Features | Overload & Phase Failure Protection |
| Application | Industrial Motor Protection |
| Manufacturer | Siemens |
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