The Siemens 3RB1246-1QM00-0FM0 is a solid-state overload relay from the SIRIUS 3RB12 series, integrating thermistor motor protection and ground-fault monitoring into a single DIN-rail mounted unit. It covers the 6.3 to 25 A adjustment range on AC 220-240 V 50/60 Hz supply, with ground-fault detection achieved through an external summation current transformer wired to the relay's inputs.
What the ratings mean for fit
The 6.3-25 A setting range matches standard IEC motor full-load currents for 4-15 kW motors at 400 V, depending on service factor. The 220-240 V AC control supply is the relay's operating voltage — not the motor voltage — so confirm panel control voltage matches. Ground-fault monitoring requires an external summation CT (not included); the relay provides the trip logic and two dedicated contacts (1 NO + 1 NC) for the ground-fault channel, separate from the overcurrent/thermistor channel which also has 1 NO + 1 NC. Both channels are monostable — they reset automatically when the fault clears and supply returns.
Integration notes
Snaps onto DIN rail per EN 60715. The external summation CT connects to the relay's dedicated terminals; the thermistor loop (PTC) connects to the motor's embedded PTC sensor chain. Both the overcurrent/thermistor and ground-fault output contacts are rated for the same control voltage as the relay supply. Verify the summation CT ratio matches the relay's ground-fault pickup setting — the relay does not include the CT.