Panel fit and switching capacity
The Siemens 3RH2122-1VB40 is a SIRIUS S00 coupling relay built for switching auxiliary circuits — think control transformers, PLC outputs, or pilot devices that need a dry-contact break. The 24 VDC coil holds at 0.85× rated and picks up to 1.85×, so it's happy on a regulated supply with some droop. Contacts are rated 10 A at 24 V and 230 V, then derate through the voltage ladder: 4.7 A at 60 V, 3 A at 110 V, 1.2 A at 220 V, 3 A at 400 V, down to 0.26 A at 600 V. That's a wide AC switching envelope for a 45 mm wide relay. Mechanical life is 30 million operations typical. AC switching frequency is 10,000 cycles per hour. Arcing time runs 10 to 15 ms; the integrated diode snubs the coil flyback.
DIN rail and wiring
Mounts via screw or snap-on onto 35 mm DIN rail — the S00 footprint is 45 mm wide, 57.5 mm tall, 73 mm deep. Clearance distances are tight: 10 mm upwards, forwards, and downwards, 6 mm at the sides. That means you can stack these in a 6 mm pitch on the rail if the panel layout is dense. Mounting position is flexible: ±180° rotation on a vertical surface, plus ±22.5° tilt forward/backward — handy for angled subpanels or swing frames. Wire terminals accept 2× 0.5–1.5 mm² solid or stranded, 2× 0.75–2.5 mm², or 2× 4 mm². Pollution degree 3 means it's rated for industrial environments with conductive dust or condensation — no need for a conformal coating in most panel builds.
Sourcing and cross-reference
This is a standard catalog item in the Siemens SIRIUS line. The closest functional peer is the 3RH2122-1WB40 — same S00 frame, same contact configuration, but with a different coil voltage.