Panel fit and ratings
The Siemens SIRIUS 3RT1034-1AH20 is a size S2 power contactor rated for 18.5 kW at 500 V under AC-3 duty, with a 10 kW rating at 690 V. It snaps onto a standard 35 mm DIN rail per EN 50022 and measures 55 mm wide, 112 mm tall, and 115 mm deep — a compact footprint for a S2 frame that leaves room for auxiliary blocks on the side, since side-by-side mounting is supported. AC-3 switching at 500 V is the headline motor-rating figure here — 18.5 kW tells you the contactor is sized for a 25 hp class induction motor on a 480 V line. The AC-2 rating of 15 kW at 400 V covers slip-ring or wound-rotor motor starts where the inrush is lower but the break current is sustained.
Termination and environment
Main circuit termination is screw-type terminals. Solid conductors accept 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), or max 2x (0.75 to 4 mm²). Stranded conductors go up to 2x (0.75 to 25 mm²) — that 25 mm² top end covers the line-side feed for a full-rated motor circuit without needing a separate terminal block. Rated for pollution degree 3, so it is suited for industrial enclosures where conductive dust or light condensation is expected. IP20 on the front, IP00 at the terminals — the terminal area is live and needs finger-safe shrouding or a cover if the panel is accessible to operators. Operating ambient range is -25 to +60 °C; storage range is -55 to +80 °C. The 60 °C top end means it can sit next to a transformer or drive in a warm cabinet without derating the coil pickup — the coil hold-in is already specified for that band.