What the ratings mean for fit
The Siemens 3RT1026-1DB44 is a SIRIUS power contactor in the S0 frame size, rated 11 kW at 400 V AC-3 and also 11 kW at 690 V AC-3 — that is the motor-switching duty class for standard squirrel-cage induction motors. The AC-3 rating is the one that governs real motor loads; the AC-4 rating of 15.5 A at 400 V covers reversing or inching duty where the contacts make and break at full load. The 24 VDC coil draws 5.4 W both on pick-up and hold, so the control transformer and wiring need to support that continuous draw — no extra inrush to size for. A varistor is built in across the coil for surge suppression, which means no external RC snubber is needed on the coil circuit.
Panel integration and mounting
Mounts via screw or snap-on onto 35 mm DIN rail per EN 50022. The S0 footprint is 45 mm wide, 88 mm tall, 150 mm deep. Side-by-side mounting is allowed with a 6 mm air gap to adjacent devices. The main circuit terminals are screw-type accepting 2x (1...2.5 mm²) stranded or 2x (2.5...6 mm²) single-core, up to 2x 10 mm² max. Control terminals accept 2x (0.5...1.5 mm²) solid or 2x (0.75...2.5 mm²) stranded, max 2x 4 mm². The enclosure is IP20 on the front, IP00 at the terminals — so the terminal area is not touch-safe without additional shrouding or panel enclosure. Pollution degree 3 suits industrial environments with conductive dust or condensation.
Coordination and fusing
For Type 2 coordination (no damage to the contactor under short circuit), Siemens specifies a gL/gG fuse rated 35 A. For Type 1 coordination (contactor may need replacement after fault), the fuse can be 100 A gL/gG. The mechanical life is 10 million operations typical. Operating temperature range is -25 to +60 °C. Maximum operating altitude is 2,000 m.