Overview
The Siemens 3RU2136-4FB0 thermal overload relay is a compact, Class 10 device designed for three-phase motor protection in industrial control systems. Part of the SIRIUS product line, this relay combines current-sensitive thermal protection with auxiliary contact switching to guard motors against overload, phase asymmetry, and phase failure. Its direct mounting on Size S2 contactors makes it ideal for space-constrained applications.
Key Features
- Class 10 Trip Accuracy: Meets IEC947 and EN60947 standards for predictable, reliable overload detection and clearance.
- Adjustable Current Range: 28–40 A setpoint covers a wide range of motor sizes with a single relay type.
- Manual/Automatic Reset: Selector switch enables either manual intervention or automatic retry after a trip event.
- Switch Position Indicator & Test Function: Visual trip indication and manual test button for quick diagnostics and commissioning.
- Temperature Compensation: Rated for operation from −20 °C to +60 °C without loss of protection integrity.
- High Impulse Voltage Resistance: 6 kV rated surge immunity protects against transient spikes in industrial environments.
Technical Specifications
- Current Rating: 28–40 A (adjustable)
- Trip Class: Class 10 per IEC60947-4-1
- Product Series: SIRIUS 3RU2
- Contactor Size: Size S2 mounting (3RT2035, 3RT2036, 3RT2037, 3RT2038)
- Connections: Main circuit and auxiliary circuit screw terminals
- Insulation Voltage: 690 V AC
- Surge Voltage Resistance: 6 kV
- Power Loss at Rated Current: 15.6 W (total); 5.2 W per pole
- Auxiliary Contacts: 1 NO + 1 NC (1 normally open, 1 normally closed)
- Reset Options: Manual or automatic via selector switch
- Operating Temperature Range: −20 °C to +60 °C
- Standards: IEC947, VDE0990, EN60947
- Approvals: UL, CSA
Typical Applications
The 3RU2136-4FB0 is specified for:
- Three-phase AC motor protection in machine tools, pumps, and fans
- Production lines and automated manufacturing systems where contactor-mounted overload relays are required
- Food, beverage, and packaging facilities requiring robust thermal motor protection
- HVAC, water treatment, and industrial utilities where IEC compliance and temperature-compensated sensing are mandated
Compatibility & Replacements
This relay mounts directly on Siemens SIRIUS 3RT2 Size S2 contactors including models 3RT2035, 3RT2036, 3RT2037, and 3RT2038. It is not interchangeable with larger SIRIUS sizes (S3, S4) or with earlier 3RU1 series devices. When upgrading or replacing an overload relay in an existing control panel, verify the contactor size and verify that manual or automatic reset mode matches the original system design.
