The Siemens 3RB1246-1EG21 is a solid-state overload relay that combines motor overload protection with integrated thermistor monitoring and internal earth-fault detection in a single device. Rated for 25 to 100 A at 110 to 120 V AC, 50/60 Hz, it provides 1NO/1NC bistable outputs for overload/thermistor and a separate 1NO/1NC set for earth fault. The bistable design means the relay latches its state after a trip, holding the fault indication even if control power is lost — useful for remote diagnostics on an unattended line.
The 25 to 100 A adjustable range covers most IEC frame-size motor starters up to about 45 kW at 400 V. The 110 to 120 V control voltage is standard for North American control transformers; check that your panel's control circuit matches before committing the BOM. The integrated earth-fault detection saves a separate ground-fault module in the MCC — one less part to source and wire. The bistable outputs (1NO/1NC for overload/thermistor, 1NO/1NC for earth fault) hold their state after a trip, so the PLC or HMI can read the fault condition even after a power cycle, which simplifies troubleshooting on a conveyor or pump line.
The lifecycle stage for this order code is listed as current. Siemens continues to manufacture and support the 3RB1246-1EG21 as an active catalog item.