What it is and what it does
The Siemens 3RT1016-1AN25 is a SIRIUS power contactor in the compact S00 frame size, designed for switching motor loads in control panels. Its 4 kW rating at 400 V AC-3 (cite:) covers the common small-motor range — pumps, fans, conveyors up to that mechanical load. The 24 VDC coil (cite:) keeps it on standard control voltages, and the screw-type terminals (cite:) accept the wire sizes you'd expect for this class: 2x 0.5 to 1.5 mm² solid, 2x 0.75 to 2.5 mm², or up to 2x 4 mm² (cite:). It snaps onto a 35 mm DIN rail per EN 50022 (cite:) and fits a 45 mm wide slot (cite:).
What the ratings mean for fit
The AC-3 rating at 400 V is the one that governs motor switching — 4 kW (cite:) means it handles the inrush and breaking of a standard squirrel-cage induction motor up to that shaft power. The AC-4 rating at 400 V, 8.5 A (cite:), covers plugging and inching duty where the contactor breaks full-load current more often; if your application involves frequent reversing or jogging, that's the number to check against your load current. The auxiliary contact block is rated 10 A at 24 V (cite:), 2 A at 60 V (cite:), 1 A at 110 V (cite:), and 0.3 A at 220 V (cite:) — these are the DC switching limits for the built-in auxiliary, so if you're driving a PLC input or a relay coil at a different voltage, verify the curve. Pollution degree 3 (cite:) means it's rated for industrial environments with conductive pollution; the IP20 finger-safe front (cite:) and terminal protection (cite:) are standard for enclosed panels. The operating range is -25 to +60 °C (cite:), so it's fine inside a non-conditioned cabinet in most climates.
Coordination and protection
For Type 2 coordination (no damage to the contactor on a short circuit), Siemens specifies a gL/gG fuse of 20 A (cite:). For Type 1 coordination (contactor may need replacement after a fault), the fuse can go up to 35 A (cite:). That's the practical guide for the panel builder: if you want to avoid pulling the contactor after a short, stay at 20 A or below. The contactor has 3 main poles (cite:) and supports side-by-side mounting with zero spacing (cite:) — no derating needed for adjacent units, which helps when packing multiple contactors into a tight row.