Siemens 3RU2146-4LD1 is a SIRIUS thermal overload relay, Size S3, with CLASS 10 trip protection.
Rated at 77 A at both 480 V and 600 V, this relay covers motor full-load currents up to that threshold. Power dissipation is 7 W per pole — three poles at 21 W total, which matters for enclosure heat rise in a sealed panel with limited convection. The auxiliary switch is integrated, with contact ratings that vary by voltage: 2 A at 24 V and 230 V, 3 A at 120 V, 1 A at 400 V. These are the make/break capacities for the signal contact — the relay's own trip mechanism is bimetallic, not dependent on the auxiliary circuit.
Stand-alone installation — no DIN rail adapter required, though it can also mount directly to a contactor. The M8 terminal bolts for the main circuit accept solid conductors from 2.5 to 16 mm² and stranded from 6 to 70 mm², covering motor leads from fractional-horsepower up to roughly 45 kW at 400 V. Any mounting position is allowed, simplifying panel layout. Temperature compensation operates from -40 to +60 °C, which means the trip curve stays within spec across the typical panel ambient range — important when the relay is near a hot contactor or in a non-climate-controlled enclosure.
Lifecycle stage is marked as current production. This is not a phase-out or NRND part — it is the active SIRIUS S3 overload relay from Siemens. No official successor exists because the part is still the current design. Substance prohibitance date of 03/01/2017 aligns with RoHS and REACH compliance timelines. The relay is manufactured for global markets; no specific UL/CSA listing is in the evidence, but the 690 V rated insulation and AC-3e rating up to 1000 V are consistent with IEC 60947-4-1 design.