The Siemens 3RH1921-1XA31-0MA3-ZX95 is a SIRIUS-series attachable auxiliary contact block, 4-pole with 3 normally-open and 1 normally-closed contacts, terminated via screw terminals. It mounts to contactors and other switching devices on EN 50012 profiles — the standard 35 mm DIN rail footprint common across SIRIUS S00, S0, and S2 sizes. The 3 NO + 1 NC arrangement gives you three make-signal paths for feedback, interlocks, or PLC inputs and one break path for a safety or stop circuit, all in a single add-on block that clips onto the front of the base contactor.
Fit and Integration
The block attaches to the front of a SIRIUS contactor or relay via the standard EN 50012 interface. Screw terminals accept solid or stranded copper: 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), and 2x 4 mm². The 3 NO + 1 NC contact arrangement is wired identically to the older 3RH1 blocks — no rewiring of the base contactor required if you are swapping a failed block. The 3RH2 successor uses the same mounting profile and terminal layout, so a panel designed for the 3RH1921-1XA31-0MA3-ZX95 can accept the 3RH2422-1AB00 (2 NO + 2 NC) without drilling or rail changes, though the contact configuration differs.