The Siemens 3RH2131-1MB40-0KT0 is a SIRIUS coupling relay — a compact auxiliary contactor built for switching control circuits, not motor loads. It gives you three normally-open instantaneous contacts rated at 10 A at 24 V AC, with the coil pulling 1.6 W DC to close and hold. Size S00 means it fits the same 45 mm wide footprint as the smallest SIRIUS contactors, so it tucks into crowded control panels alongside the main power contactors without wasting rail space.
Switching ratings across the voltage range — what actually matters
Those lower currents at higher voltages reflect the arc-quenching limits of the contact gap — the 600 V rating is there for signal-level isolation, not for power switching.
Mounting and spacing — clearances for the wireman
The 73 mm depth includes the terminals, so budget that plus finger space when laying out the backplane. The degree of pollution 3 rating means it's suitable for industrial enclosures where conductive dust or occasional condensation is expected.
Lifecycle and sourcing — what you need to know for the BOM
RoHS compliance date is marked as 10/01/2009, and the storage temperature range of -55 to +80 °C covers most warehouse conditions. The operating ambient is -25 to +50 °C, which is typical for indoor control panels without direct heat sources nearby.