SIEMENS
SIEMENS 3RU21161FB0 Overload Relay 3.5-5 A
Thermal overload relay with 3.5 A to 5 A range, 690 V AC rating, trip class 10, and direct contactor mounting
- Thermal overload protection for 3.5–5 A motors
- Trip Class 10 ensures reliable motor protection
- Auto and manual reset options for flexibility
- Direct contactor mounting simplifies installation
- Screw terminals provide secure wiring connections
SIEMENS 3RU21161FB0 Overload Relay
The SIEMENS 3RU21161FB0 is a thermal overload relay designed for motor protection in industrial control panels. It suits maintenance engineers and panel builders who need reliable overload detection for three-phase motors. The unit operates across a 3.5 A to 5 A current setting range with Trip Class 10 response. It mounts directly to compatible SIRIUS contactors in frame size S00.
Direct contactor mounting with screw terminals
This relay mounts directly onto a SIRIUS series contactor, eliminating the need for separate DIN-rail space and additional wiring between devices. Screw terminals accept standard ring or fork lugs for secure power and control connections. The assembly includes the required three thermal units, so no extra parts are needed for the protection function. One normally open and one normally closed auxiliary contact provide status signalling to a PLC or indicator lights.
Thermal Trip Class 10 behaviour under sustained load
Under a sustained overload the thermal elements heat gradually, tripping the relay in accordance with Trip Class 10 timing to protect motor windings from prolonged excess current. The auto and manual reset options let operators choose between automatic restart after cooling or a deliberate manual reset for safety inspection. The 690 V AC maximum voltage rating covers common industrial supply voltages. The relay is not suited for applications requiring electronic overload features such as phase-loss detection or communication modules.
Highlights
- Thermal overload protection for 3.5–5 A motors
- Trip Class 10 ensures reliable motor protection
- Auto and manual reset options for flexibility
- Direct contactor mounting simplifies installation
- Screw terminals provide secure wiring connections
Specifications
| Brand | SIEMENS |
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Questions about this item
At what current does the relay trip during a prolonged overload?
The relay trips at currents between 3.5 A and 5 A, adjustable within that range.
How much heat does the relay generate during continuous operation?
As a thermal overload relay it produces heat proportional to the load current; it is rated for Trip Class 10 at up to 690 V AC.
Which contactor frame size must the buyer already have for direct mounting?
It mounts directly onto SIRIUS Series contactors with Frame Size S00.
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