What it is and where it fits
The Siemens 3RT1026-1AM20-0UA0 is a SIRIUS power contactor in size S0, rated for motor switching duty. It delivers 11 kW at 400 V in AC-2 use (slip-ring motors, moderate overloads) and carries a 15.5 A continuous rating in AC-4 (plugging, inching, reversing). That AC-4 number is the one to watch if your application cycles the motor under load — it's the thermal limit for frequent reversals. Mounts on a 35 mm DIN rail per EN 50022, screw or snap-on. At 45 mm wide and 85 mm tall, it fits a standard S0 footprint — same slot as other SIRIUS S0 contactors, so swapping one in doesn't force a panel layout change.
Ratings and what they mean for the panel
The AC-2 motor rating of 11 kW at 400 V covers most medium-duty pump and fan loads. For type 2 coordination (fault withstand without welding), the spec calls for a 35 A gL/gG fuse upstream. If you're running type 1 coordination (replace contactor after fault), a 100 A fuse is allowed — that's a wide window for selectivity with upstream breakers. Pollution degree 3 means it's rated for industrial environments with conductive dust or occasional condensation — typical for an unsealed panel. Operating temperature range is -25 to +60 °C, so it handles a hot cabinet near a furnace line without derating. Screw terminals on the main circuit accept up to 2x 10 mm² or 1x AWG 8. The auxiliary circuit (if fitted) uses the smaller 0.5–4 mm² range. That's enough for a 35 A feeder on the mains and standard 1.5 mm² control wiring.