Part identity and mounting
The Siemens SIRIUS 3RT2028-2CL24-3MA0 is a size S0 power contactor with a 24 VDC coil, spring-type coil terminals, and a screw and snap-on mounting onto 35 mm DIN rail per DIN EN 60715. Dimensions are 102 mm height, 45 mm width, and 144 mm depth — the depth is the dimension that projects from the DIN rail, so panel clearance behind the rail needs at least 144 mm.
Auxiliary contacts and ratings
The contactor carries a 1 NO + 1 NC auxiliary contact block (18...8 configuration for main contacts), with no separate auxiliary switch module. Auxiliary contact ratings are specified at several voltages: 6 A at 24 V, 2 A at 48 V, 2 A at 60 V, 1 A at 110 V, 0.9 A at 125 V, 0.3 A at 220 V, 3 A at 400 V, and 0.6 A at 440 V — these are the make/break capacities for the auxiliary contacts, not the main power path. Mechanical life is typical 10,000,000 operations.
Switching frequency and coil data
Maximum switching frequency: 1,000 1/h at AC-1, 750 1/h at AC-2, AC-3, and AC-3e, and 250 1/h at AC-4. Coil operating range: at 50 Hz the coil draws 0.25 A, at 60 Hz 0.28 A (likely the holding current). The arcing time is 10 ms.
Environmental and wiring
Main circuit terminals accept solid or stranded wire 1…10 mm²; auxiliary terminals accept 2x (0.5…2.5 mm²) solid or stranded.