Overload relay for S00/S0 motor starters
The Siemens 3RB1246-1PB00 is a SIRIUS overload relay sized for full motor protection in S00 or S0 contactor frames, covering the 1.25 to 6.3 A adjustment range. It's a stand-alone unit — mounts directly on the contactor or on a DIN rail, with straight-through main circuit wiring and screw terminals on the auxiliary circuit. The trip class is selectable from 5 to 30, so you match the thermal curve to the motor start profile: Class 5 for fast-starting pumps, Class 10 for standard induction motors, Class 20 or 30 for high-inertia loads like fans or centrifuges.
The 1.25–6.3 A range fits fractional-horsepower to small 3-phase motors — think 0.37 kW to 2.2 kW at 400 V. The straight-through main circuit means the power wires pass directly through the relay without looping, keeping the panel layout clean and reducing wiring errors. Auxiliary connections are screw-type, so a standard slotted or Pozidriv driver on the van gets the job done.
Reset options and signaling
This relay supports manual, automatic, and remote reset — the standard SIRIUS three-position selector on the front. Monostable outputs mean the relay drops its contacts when power is removed, so a control system sees a clean off-state. The ground-fault signaling output is a separate circuit, not just a spare auxiliary contact — it's specifically for indicating a ground leak, which helps a maintenance tech isolate a wet motor or degraded cable without chasing phantom trips.