What it is and where it fits
The Siemens 3RH1131-1BC40 is a SIRIUS auxiliary contactor with three normally-open (3 NO) instantaneous contacts, sized in the S00 frame. It is designed for control-circuit switching — signalling, interlocking, and logic functions inside a motor control centre or panel — not for direct motor loads. The 45 mm width and screw-and-snap-on mounting let it land on a DIN rail alongside a SIRIUS contactor or as a standalone block.
Contact ratings — what they mean for your circuit
The contact ratings are given by operating voltage because the switching capacity of a control-circuit contact depends on the voltage it interrupts. At 24 V the contacts carry 10 A; at 230 V they carry 6 A; at 400 V they carry 3 A; and at 690 V they carry 1 A. These are the thermal current ratings (Ith) for the respective AC voltages — the actual make/break capacity in a given duty class (AC-15 for solenoid loads, AC-14 for resistive) will be lower. For a 24 VDC control loop the coil holding power is 3.2 W, so the 10 A rating leaves generous headroom for multiple pilot devices.
Mounting and integration
Screw and snap-on mounting onto 35 mm DIN rail. The mounting position allows ±180° rotation on a vertical surface and ±22.5° tilt forward/backward, so it fits in tight enclosures or angled sub-panels. Wire sizes accepted: two conductors of 0.5–1.5 mm², two of 0.75–2.5 mm², or a single 4 mm² — spring-cage or screw terminals depending on variant (this order code uses screw terminals). IP20 on the front means it is protected against finger contact but not against moisture; keep it inside a closed panel.
Environmental and compliance
Operating temperature range -25 to +60 °C; storage and transport -55 to +80 °C. Shock resistance rated at 10g / 5 ms and 5g / 10 ms. Surge voltage resistance 6 kV. Pollution degree 3 (conductive pollution or dry non-conductive pollution that becomes conductive due to condensation). RoHS compliance date 01.07.2006 — the part meets the original RoHS directive. Contact reliability: one incorrect switching operation per 100 million operations at 17 V, 1 mA, which is the standard for dry-circuit (low-energy) signal reliability.