Siemens 3RU21261HB0 5.5-8A Thermal Overload Relay

Siemens SIRIUS 3RU21261HB0 Thermal Overload Relay

A compact motor protection device for small three-phase motors. Designed to mount directly onto Siemens S0‑size contactors, it saves space and simplifies installation.

Key Specs

Adjustable Current Range: 5.5 to 8 A Trip Class: Class 10 (trips in about 10 seconds under overload) 

Mounting: Attaches directly to Siemens 3RT S0 contactors via screw terminals 

Reset & Test: Manual or automatic reset with a built-in STOP button, TEST function, and visible trip indication 

Environmental Range: Operates between - 20 °C and +70 °C (some sources allow –40 °C) 

Main Benefits

Protects motors from overheating and phase failure

Easy to mount directly onto compatible Siemens contactors

Compact size saves panel space

Simple to test and reset- clear trip indicator

Common Applications

Three-phase motor starter panels

HVAC control systems

Pumps, compressors, fans

Any compact industrial motor protection setup