What the 4 NC contacts mean for your control circuit
The 3RH2911-1GA04-ZW97: This is a front-mounted auxiliary switch block for Siemens SIRIUS contactor relays — specifically the 3RH2140 and 3RH2440 frames (EN 50011 keyed). It carries four normally-closed contacts, wired as 51/52, 61/62, 71/72, 81/82, with screw-type terminals. The NC configuration means the contacts are closed when the relay coil is de-energized — useful for safety interlock circuits, status feedback on a dropped-out contactor, or anti-tie-down logic where the closed state must be verified before a start sequence. Rated 10 A maximum, but the real switching capacity depends on the voltage and duty: at 24 V AC-15 it handles 10 A, at 110 V it drops to 3 A, and at 440 V it's 0.5 A. The 690 V AC-15 rating is 1 A — that's the ceiling for inductive pilot-duty loads at high voltage.
Snap-on DIN rail fit and panel space
Snap-on mounting to standard DIN rail — no screws needed. The block is 36 mm wide, 43.7 mm deep, 37.5 mm high, so it takes up one standard 36 mm module slot on the rail. Terminal capacity is 2x (0.5...1.5 mm²) and 2x (0.75...2.5 mm²) per clamp, or 2x (20...16) and 2x (18...14) AWG. The screw terminals are open-front — a Pozidriv #1 driver reaches them without removing the block. IP20 on the front means finger-safe from the panel face; the rear is open to the DIN rail cavity. No washdown rating — keep it inside a closed enclosure.
Lifecycle and sourcing — active, but multi-unit packaging
Mechanical service life is 10 million switching cycles typical. Contact reliability is 1 faulty switching per 100 million operations at 17 V, 1 mA — that's the low-energy threshold where oxide films on silver contacts can cause intermittents. Quoted to order against your BOM quantity. Availability and current pricing confirmed at RFQ time — the spread is in the volume break, not the unit price.