The Siemens SIRIUS 3RU5136-4HB1 is a thermal overload relay rated 50 A operational current, adjustable from 40 to 50 A, with a Class 10 trip characteristic. It is designed for three-phase motor protection in industrial control panels, combining with the S2-size contactor frame. The operating voltage is rated 690 V at 50-60 Hz, and it mounts stand-alone with a vertical mounting surface that allows ±135° rotation and ±45° tilt.
The 40-50 A adjustable current range covers the full-load amps of a 22-30 kW motor at 400 V (roughly 45-55 A FLA), so this relay directly protects that motor class.
Panel and mounting considerations
This relay installs stand-alone — it does not require a separate mounting base. The mounting position allows ±135° rotation and ±45° tilt from vertical, giving flexibility in tight enclosures. Required spacing to grounded parts at the side is 6 mm, so plan for that gap when laying out the DIN rail. Main contacts use screw-type terminals with a tightening torque of 3-5 N·m, accepting 2x (0.5-1.5 mm²) solid or stranded, or 2x (0.75-2.5 mm²) finely stranded with ferrules. For AWG, that's 2x (18-3) for main and 2x (20-16) for auxiliary contacts.
Auxiliary circuit and short-circuit protection
For the auxiliary switch circuit, the required short-circuit protection is a gL/gG fuse rated 6 A, or a quick-acting fuse rated 10 A. The auxiliary contacts use screw-type terminals. This relay has three poles for the main current circuit, with electrical connectors arranged top and bottom. The insulation voltage at degree of pollution 3 is rated 690 V AC.