The Siemens SIRIUS 3RT1326-1AN20 is a size S0 power contactor with four normally-open main contacts, rated for motor switching at 11 kW in AC-2 duty at 400 V. That AC-2 rating covers wound-rotor motors and moderate overloads — the kind of load profile you see on conveyors and pumps that cycle under partial load. The contactor snaps onto a 35 mm DIN rail per EN 50022 and uses screw-type terminals on the main circuit. Front-side protection is IP20; the terminal area is IP00, so keep live parts behind a panel door or enclosure.
Ratings and what they mean for fit
The headline motor rating is 11 kW at 400 V AC-2. That is the load it can switch repeatedly under the moderate inrush of a slip-ring or wound-rotor motor. For AC-3 duty (squirrel-cage motors with higher inrush), the rating will be lower — always check the specific AC-x column when matching to a motor nameplate. The contactor also carries a 10 A rated operational current at 24 V for resistive or lightly inductive control loads. Coil holding voltage is nominal 24 V; the dropout threshold sits below 18 V, which is standard for this class. The contactor is rated for pollution degree 3, meaning it is suited for industrial environments where conductive pollution or dry non-conductive pollution that becomes conductive due to condensation can occur. Operating temperature range is -25 to +60 °C, so it handles warm panel interiors without derating at the lower end. Maximum operating altitude is 2 000 m — beyond that, air density drops and dielectric withstand and cooling both degrade. Main circuit terminals accept solid conductors from 2x 0.5 to 1.5 mm² up to 2x 0.75 to 4 mm², and stranded from 2x 1 to 2.5 mm² up to 2x 2.5 to 6 mm², with a maximum of 2x 10 mm². Dimensions: 85 mm high, 61 mm wide, 91 mm deep. The 61 mm width is the S0 frame standard — it occupies three 18 mm module positions on a DIN rail. Side-by-side mounting is permitted with zero clearance, but the 6 mm side clearance to grounded metal parts must be maintained for arc flash containment.
Coordination and protection
For Type 1 coordination (no damage to the contactor but may need contact replacement after a fault), the required upstream fuse is gL/gG 63 A. For Type 2 coordination (contactor remains operational after a fault), the fuse is gL/gG 35 A. These ratings assume a prospective short-circuit current typical of industrial distribution. Always verify the available fault current at the installation point against the contactor's rated short-circuit making and breaking capacity.