Siemens 3RT2027-2NB30 SIRIUS Power Contactor — Size S0, 24 VDC Coil, Spring-Terminal
It carries a 24 VDC coil rated 21–28 V with an inrush peak of 3 A and a holding current draw of 0.7 A initial, then settling to a full-scale value of 1.3 A. The main contacts are rated for AC-3 duty at 750 operating cycles per hour maximum, with a mechanical life of 10 million operations typical. Spring-type terminals accept solid or stranded conductors from 1 to 10 mm² on the main circuit, and 2 × 0.5 to 2.5 mm² for auxiliary wiring. The contactor mounts via screw or snap-on to 35 mm DIN rail per DIN EN 60715, occupying 45 mm of panel width with a depth of 107 mm and height of 102 mm. Clearance requirements: 10 mm upward, forward, and downward; 6 mm at the sides. An auxiliary switch is included.
The contactor's switching capacity varies by duty class. For AC-2 and AC-3 (motor starting and running) the rate is 750 cycles per hour, and for AC-4 (plugging, inching) it drops to 250 cycles per hour. The AC-3e rating also permits 750 cycles per hour. These rates define the thermal limits of the contactor under repeated switching — exceeding them accelerates contact wear. Operating times are consistent across AC and DC coil supplies: 30 to 50 ms for both make and break. Arcing time is a tight 10 ms. The power factor at 50 Hz is 0.86; at 60 Hz it is 0.82. Auxiliary contact ratings: at 24 V rated value, 10 A; at 48 V, 2 A; at 60 V, 2 A; at 110 V, 1 A. The main contact configuration is listed as 18... 8, indicating normally-open and normally-closed pole counts.