The Siemens SIRIUS 3UG4501-2AW30 is a level monitoring relay with analog setting — it watches a conductive liquid level (or any resistive probe path) and switches its output when the level crosses the set point. The rated supply voltage covers 24 to 240 V AC/DC, so it works on control transformers or direct from a 24 VDC panel supply without a separate power module. The output relay is rated 3 A at 250 V AC (50/60 Hz) and the same at 400 V, giving enough contact margin for piloting a contactor coil or a small pump directly. The start-up delay is adjustable from 0.5 to 10 seconds, which helps avoid nuisance trips on filling cycles or turbulent surfaces. IP20 protection means it belongs inside an enclosure, not out on the tank.
The 24-240 VAC/DC rated supply means it can be wired into a 120 V or 230 V control circuit without a transformer, or run on 24 VDC if that's your panel standard. The 3 A contact rating at 250 V is enough for most pilot-duty loads; if you're switching a motor starter coil, check the inrush against the relay's make/carry capacity — the 3 A continuous rating is thermal, not inductive. The external reset input allows remote reset from a PLC or pushbutton, handy for unattended pump stations. The adjustable start delay (0.5-10 s) and the full-scale value setting (1.1) give you tuning range for different probe resistances and tank geometries.