What it is and where it fits
The Siemens 3RH2911-1GA13-ZW98 is a SIRIUS auxiliary switch block that snaps onto the front of 3RH2 contactor relays — specifically the 3RH2140 and 3RH2440 frames, per the EN 50011 contact arrangement standard. It gives you one normally-open and three normally-closed auxiliary contacts, wired out to terminals 53/54, 61/62, 71/72, and 81/82, all screw-type. Physically coded so it only fits the right relay body — no guessing on the panel.
Contact ratings — what they mean for your circuit
The block is rated for a maximum of 10 A, but the real working current depends on the voltage and duty. At 24 V it handles 6 A; at 230 V it also carries 6 A; at 400 V it drops to 3 A. For inductive loads under AC-15 at 690 V, the rated value is 1 A — that's the figure to use for solenoid or contactor coil switching. The DC ratings are lower: at 24 V DC it's 10 A, at 60 V DC it's 4.7 A, at 110 V DC it's 3 A, and at 600 V DC it's just 0.26 A. So for a 24 V DC pilot circuit you're fine at 10 A, but step up to 110 V DC and you're limited to 3 A.
Mounting and panel fit
Snap-on mounting to the front of the contactor relay — no tools, no DIN rail required for the switch itself. The block dimensions are 36 mm wide, 37.5 mm high, and 43.7 mm deep, so it adds about 44 mm to the relay's depth. IP20 on the front means it's protected against finger contact but not against moisture; keep it inside the enclosure. Screw terminals accept 2x (0.5…1.5 mm²) or 2x (0.75…2.5 mm²) solid or stranded, or AWG 20–16 and 18–14. Strip length is not stated, but standard practice is 8–10 mm for this terminal type.
Durability and reliability
Mechanical service life is rated at 10 million switching cycles typical. Contact reliability is specified as 1 faulty switching per 100 million operations at 17 V and 1 mA — that's the dry-circuit performance for low-level signal switching. Surge voltage resistance is 6 kV, and insulation voltage at pollution degree 3 is 690 V AC. Operating temperature range is -25 to +60 °C; storage from -55 to +80 °C.