Solid-state overload relay with integrated thermistor and ground fault monitoring
The Siemens 3RB1262-0LG00-0FM0 is a solid-state overload relay that integrates thermistor motor protection and ground fault monitoring into a single device, covering a current range of 205 to 820 A AC at 110 to 120 V, 50/60 Hz. Ground fault detection is handled through an external summation current transformer (Kloeckner-Moeller ZWA820), and the relay provides one normally open and one normally closed contact for the overcurrent/thermistor channel, plus a separate 1 NO/1 NC set for ground fault indication. This is a monostable relay, meaning the contacts return to their de-energized state when the fault clears or power is removed.
The 205 to 820 A current range covers medium-to-large motor loads — think 100–400 kW induction motors on pumps, conveyors, or compressors — where a standard bimetallic relay would drift or nuisance-trip. The solid-state design eliminates thermal lag, so it tracks the motor's actual thermal state cycle by cycle. The 110–120 V AC control voltage is common in North American control panels; verify your control transformer matches before wiring. Ground fault monitoring via an external summation CT means you can detect leakage down to a few hundred milliamps without a separate ground-fault relay — useful on ungrounded or high-resistance-grounded systems where a single phase-to-ground fault won't trip the upstream breaker.
This is a DIN-rail-mount solid-state relay, sized for the standard 35 mm rail inside an enclosure. The external summation current transformer (Kloeckner-Moeller ZWA820) needs its own DIN footprint nearby — plan for that in your panel layout. The 1 NO/1 NC contact sets for overcurrent/thermistor and ground fault are electrically isolated, so you can wire them into separate safety circuits or a PLC input card without commoning the returns.