What it is and what it does
The Siemens 3RT1026-1AF04 is a SIRIUS power contactor in the S0 frame size, with three normally-open main contacts and screw-type terminals for the main current circuit. It mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 50022, so it drops straight into a standard panel rail without adapters. The S0 frame is the compact workhorse of the SIRIUS contactor line — 45 mm wide, 85 mm tall, 140 mm deep — sized for motor switching and general load control in control cabinets where panel space is tight but you still need full-rated breaking capacity.
What the ratings mean for your panel
The 3RT1026-1AF04 carries a pollution degree 3 rating, meaning it's designed for industrial environments where conductive dust or condensation can occur — no derating needed for the typical factory floor. The operating temperature range of -25 to +60 °C covers most indoor installations without additional climate control. Wire termination uses screw-type terminals accepting 2x (0.5 to 1.5 mm²), 2x (0.75 to 2.5 mm²), or up to 2x 4 mm² solid, with AWG equivalents of 2x (16 to 12), 2x (14 to 10), and 1x 8. That's enough cross-section for the full rated current without pigtailing or reducing the conductor. The contactor is rated for side-by-side mounting without derating, so you can pack multiple units on the same DIN rail at the standard 6 mm spacing between units. The front side carries IP20 finger-safe protection; the terminal area is IP00, so live parts are exposed during wiring — standard practice, but note it for panel labeling.