SIEMENS
SIEMENS 3RU21264NB0 Overload Relay 23-28 A 690 V AC Trip Class 10
Thermal overload relay protects three-phase motors at 23-28 A with 690 V AC rating and Trip Class 10
- Thermal protection for 23–28 A motor circuits
- Trip Class 10 ensures rapid overload response
- 690 V AC rating suits industrial power systems
- Direct contactor mounting simplifies panel assembly
- Screw terminals give secure, tool-friendly wiring
Application and fit
The SIEMENS 3RU21264NB0 is a three-pole thermal overload relay designed for direct mounting on SIRIUS S0 contactors. It protects three-phase motors by monitoring current between 23 A and 28 A with a Trip Class 10 response. The unit includes thermal units and offers both auto and manual reset modes for operational flexibility.
Current setting range
The decisive specification is the adjustable overload range of 23 A minimum to 28 A maximum. Select this relay only when the motor full-load current falls inside that window; a lower or higher setting requires a different relay. The 690 V AC maximum voltage rating covers standard industrial three-phase supplies.
Thermal behaviour and power
Thermal operation means the relay trips on sustained overcurrent without external control power, so heat dissipation is limited to the contactor mounting interface. Screw terminals provide secure connections for the power circuit and the 1NO/1NC auxiliary contacts. Normal use adds negligible noise and minimal watt loss to the starter assembly.
Highlights
- Thermal protection for 23–28 A motor circuits
- Trip Class 10 ensures rapid overload response
- 690 V AC rating suits industrial power systems
- Direct contactor mounting simplifies panel assembly
- Screw terminals give secure, tool-friendly wiring
Specifications
| Brand | SIEMENS |
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Questions about this item
What does the 23-28 A setting range mean once the relay is installed on a motor circuit?
The relay protects motors drawing between 23 A and 28 A; set the dial to the motor's full-load current and it will trip on overload within Trip Class 10 timing.
How does the 690 V AC rating limit the contactor and circuit voltage you can use with this relay?
The 690 V AC maximum applies to the main power circuit; the contactor and supply must not exceed this voltage, while the auxiliary contacts switch separate control circuits.
What does the direct-to-contactor mounting style require on the contactor side?
The relay snaps onto a compatible SIRIUS S0 frame contactor using the integrated mounting feet; no separate base or DIN rail clips are needed.
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