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Siemens 3RU21161KB0 overload relay, grey plastic housing with screw terminals

SIEMENS

SIEMENS 3RU21161KB0 Overload Relay 9-12.5A 690V AC Trip Class 10

SKU CH-DF36-092DR

Thermal overload relay protects motors at 9–12.5 A with 690 V AC rating and Class 10 trip

  • Thermal protection up to 12.5 A trip class 10
  • Dual auxiliary contacts 1NO/1NC for status signaling
  • Direct contactor mounting with screw terminals
  • Auto and manual reset modes included
  • Rated 690 V AC for industrial circuits

Overload Relay 9-12.5 A

The SIEMENS 3RU21161KB0 is a thermal overload relay designed for motor protection in industrial control circuits. It suits maintenance engineers and panel builders wiring three-phase starters up to 690 V AC.

Current Setting Range 9 A to 12.5 A

The adjustable dial covers 9 A minimum to 12.5 A maximum, matching Trip Class 10 response for standard motor acceleration. Motors drawing sustained current above 12.5 A exceed the relay’s calibration limit and will nuisance-trip.

Direct Contactor Mounting Screw Terminals

The unit mounts directly to a compatible SIRIUS S00 contactor using screw terminals for power and auxiliary 1NO/1NC contacts. Installers without that contactor frame or preferring DIN-rail mounting must source separate adapters.

How it compares

Measured against everything we stock in Contactors, Relays & Motor Starters, at today’s prices. Recalculated every night.

Price $55.99
Cheaper than about 54% of the 1,098 comparable items (median $61.99).

Specifications

Product
Brand nameSIEMENS

Questions about this item

Will the 3RU21161KB0 mount directly to an existing SIRIUS S00 contactor without extra brackets?

Yes, the relay uses direct-to-contactor mounting and is compatible with the SIRIUS series frame size S00, so it fits existing S00 contactors without additional hardware.

How can I verify the overload relay is operating correctly after installation?

Set the current dial between 9 A and 12.5 A, apply load, and confirm the relay trips at the configured value with Trip Class 10 timing; the 1NO/1NC auxiliary contacts will change state to signal the trip.

Does the package include the three thermal units required for three-pole protection?

Yes, the relay includes thermal units, and the specification calls for three required thermals matching the three poles.

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