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

Certified for global use (UL, CSA, CE, EAC, CCC) 

 

Common Applications

Three-phase motor starter panels

HVAC control systems

Pumps, compressors, fans

Any compact industrial motor protection setup