What it is and what it does
The Siemens SIRIUS 3RT1015-1VB42 is a power contactor in the S00 frame size, designed for switching motor loads and resistive loads in control panels. It mounts on a 35 mm DIN rail per EN 50022, with screw and snap-on fixing, and occupies 45 mm of panel width. The coil is rated 24 VDC and includes a built-in diode surge suppressor, so you don't need an external flyback diode across the coil terminals — the holding power is a steady 1.4 W, which keeps heat dissipation low in a crowded enclosure. Switching capacity covers a range of motor duties: at AC-3 (standard motor start/run) it handles 3.5 kW at 500 V and 4 kW at 690 V. For resistive loads (AC-1) the maximum operating current is 10 A at 24 V and 6 A at 230 V. The contactor is also rated for AC-4 (plugging/reversing) at 6.5 A at 400 V. Mechanical life is 30 million operations typical. Operating temperature range is -25 to +60 °C, maximum altitude 2,000 m.
Wiring and coordination
Main power terminals are screw-type, accepting 2 x (0.5 to 1.5 mm²), 2 x (0.75 to 2.5 mm²), or up to 2 x (0.75 to 4 mm²) solid or stranded conductors. AWG equivalents are 2 x (20 to 16), 2 x (18 to 14), and 1 x 12. Side-by-side mounting is allowed with a 6 mm clearance to adjacent devices. Short-circuit protection: with Type 1 coordination, use a gL/gG fuse rated up to 35 A. For Type 2 coordination (no damage to the contactor after a fault), the fuse must be limited to 20 A gL/gG. This matters when you're coordinating with upstream breakers in a motor control center. Pollution degree 3 means the contactor is suitable for industrial environments with conductive pollution or dry non-conductive pollution that becomes conductive due to condensation. No special conformal coating required for typical panel use.
Lifecycle and sourcing
The 24 VDC coil with diode suppression is a common variant, and the S00 frame is widely used in light industrial control.