The Siemens 3RU1126-4BB0 is a SIRIUS thermal overload relay in size S0, designed for motor protection with CLASS 10 trip characteristics. The IP20 protection on the front means the relay is touch-safe against finger contact, suitable for enclosed panels; the open design relies on the cabinet for environmental sealing, not the device itself.
The ATEX approval (DMT 98 ATEX G 001) covers use in potentially explosive atmospheres, which adds a documentation requirement for pharmaceutical or chemical process lines. Substance prohibitance date of 01.07.2006 confirms compliance with RoHS-style material restrictions — the relay contains no prohibited substances above threshold as of that date, which satisfies the materials declaration for most quality-management systems.
Mounting position is flexible: the relay can be installed on a vertical surface with ±135° rotation or ±45° tilt front/back, which simplifies panel layout when the contactor is oriented at an angle to fit cable ducts or gland plates. Dimensions are 45 mm wide, 97 mm high, 96 mm deep, fitting the standard S0 footprint — it occupies the same slot as the corresponding SIRIUS contactor (e.g., 3RT602x series), so no extra panel width is needed for the overload relay. Clearance requirements: 0 mm upwards, forwards, backwards, and downwards, with 6 mm at the side — this means the relay can be stacked directly against adjacent devices vertically, but needs a 6 mm air gap laterally for heat dissipation and arc-flash clearance. Wire ranges: solid and finely stranded conductors from 0.5 to 2.5 mm² (2× per terminal) for main and auxiliary circuits, with AWG equivalents of 2×(16…12) and 2×(14…8) for main contacts, and 2×(20…16) and 2×(18…14) for auxiliary contacts — screw terminals accept ferruled or solid wire, no bootlace ferrule required for the stranded sizes listed.
Power dissipation per pole is 2.7 W, which totals 8.1 W for the three-pole unit at full load — this heat must be considered in the panel thermal budget, especially when multiple starters are ganged in a small enclosure without forced ventilation. The auxiliary contact ratings cover multiple control voltages: 1 A at 24 V, 3 A at 120 V, 2 A at 230 V, 1 A at 400 V, plus lower values for 110 V, 125 V, and 220 V — these are the make/break capacities for the N/O and N/C auxiliary contacts that signal trip status to a PLC or annunciator. Environmental range: operating temperature -20 to +70 °C, storage/transport -55 to +80 °C, with 100 % relative humidity during operation — suitable for unconditioned plant-floor cabinets but not for direct outdoor exposure without a weatherproof enclosure. Shock resistance rated at 8g for 10 ms, which is typical for fixed-installation industrial gear — the relay can withstand vibration from nearby crushers or compressors without nuisance tripping, provided it is mounted on a rigid panel.