What this auxiliary switch does on a 3RT2 or 3RH2 base
The 3RH2911-1HA02-ZW98: This is a front-mounted auxiliary switch block for Siemens SIRIUS contactors (3RT2) and contactor relays (3RH2). It adds two normally-closed (NC) contacts to the base device, wired via screw-type terminals that accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) conductors, or 2x (20 to 16) and 2x (18 to 14) AWG. The snap-on mounting means it clips directly onto the front of the contactor or relay without tools — no extra DIN rail space needed. The IP20 front protection is standard for enclosed panels; keep the panel door closed during operation.
Current ratings across the voltage range — what they mean for your circuit
The maximum thermal current is 10 A, but the real switching capacity depends on the voltage and load type. At 24 V AC-15 (solenoid/contactor coil duty) it switches 6 A; at 230 V AC-15 it handles 6 A; at 400 V AC-15 it drops to 3 A. For DC loads, the 24 V rated value is 10 A, but at 220 V DC it falls to 1.2 A, and at 600 V DC it's just 0.26 A. The contact reliability spec — one faulty switching per 100 million operations at 17 V, 1 mA — means this switch handles low-signal PLC inputs reliably, not just power circuits. The mechanical life of 10 million switching cycles covers most panel applications for years.
Panel fit and environmental limits
Dimensions are 36 mm wide, 37.5 mm high, 43.7 mm deep — it adds about 44 mm to the front of the contactor. Operating temperature range is -25 to +60 °C; storage range is -55 to +80 °C. The insulation voltage is rated 690 V AC with pollution degree 3, and surge voltage resistance is 6 kV — suitable for 400 V line-to-line panels with proper clearance.