The Siemens 3RU5136-4GB1 is a SIRIUS thermal overload relay rated at 45 A operational current, adjustable from 36 to 45 A via the current-dependent overload release. The thermal bimetal design responds to actual motor heating, not just instantaneous current, so nuisance tripping on moderate overloads is kept to a minimum. This relay is paired with a contactor of frame size S2 (Siemens-specific sizing), installed stand-alone or directly coupled. The main circuit uses screw-type terminals accepting 2×(0.5–1.5 mm²) solid/stranded or 2×(0.75–2.5 mm²) finely stranded with ferrules, with a tightening torque of 3 to 5 N·m. Auxiliary and control circuits also use screw terminals, wired with 2×(0.5–1.5 mm²) or 2×(0.75–2.5 mm²).
The 45 A rating and 36–45 A adjustment range determine which motor this relay protects: it covers motors with FLA between 36 and 45 A at 50/60 Hz. The 690 V rated operational voltage and 6 kV surge voltage resistance mean it is suitable for 400 VAC and 480 VAC systems with adequate clearance. The 9 W typical power loss — 15.6 W at rated current in hot operating state — matters for enclosure thermal budgeting; at 5.2 W per pole, a panel with multiple relays needs ventilation or derating above 40 °C. Mounting position is flexible: the relay can be installed with a vertical mounting surface, rotatable ±135° or tiltable ±45° to front and back. It requires 6 mm clearance to grounded parts at the side. For short-circuit protection of the auxiliary switch, use a gL/gG fuse rated 6 A or a quick-acting fuse rated 10 A. The part is rated for installation altitudes up to 2000 m above sea level.
Integration notes
The relay measures 55 mm wide by 105 mm high by 118 mm deep. Stand-alone installation means it mounts directly on the DIN rail or panel plate without a contactor base, though it is intended to couple with a SIRIUS S2 contactor. Screw terminals on top and bottom allow straightforward wiring: main conductors enter the top, exit the bottom. For auxiliary contacts, AWG 18–14 is handled by the screw terminals. Ambient operating temperature spans –20 to +70 °C; storage/transport from –55 to +80 °C. The relay withstands 8g shock for 10 ms per IEC 60068-2-27.