The Siemens SIRIUS 3UG4816-2AA40 is a network monitoring relay with digital setting, designed to monitor phase parameters in three-phase AC systems. It detects phase loss, phase sequence, and asymmetry, and can also monitor undervoltage or overvoltage — five selectable functions in one 22.5 mm-wide housing. The LCD display shows the measured values and settings directly, so you can read line conditions without a separate meter.
Rated control supply voltage is 24 V AC/DC. The output relay contacts are rated 3 A at 250 V and 400 V at 50/60 Hz, with lower ratings for DC loads: 1 A at 24 V, 0.2 A at 125 V, 0.1 A at 250 V. That means the relay can switch small motor starters, contactors, or signal lamps directly in most control panels. The asymmetry detection catches a blown fuse or a lost phase before the motor overheats — a common failure mode in aging distribution. The 22.5 mm width and snap-on mounting let it clip onto standard DIN rail without drilling. Depth is 91 mm, height 103 mm — fits most enclosures without crowding the gland plate. Operating temperature range is -25 to +60 °C, storage -40 to +85 °C. Pollution degree 2 covers normal industrial environments with non-conductive contamination. IP20 means finger-safe but not washdown; keep it inside a panel. The relay offers an adjustable start-up delay (0 to 999.9 s,) to ride through momentary dips, plus delayed switching and auto-reset or external reset options. IO-Link communication at COM2 (38.4 kBaud,) allows parameter readback and remote monitoring — useful if you are integrating into a higher-level SCADA or PLC system. The LCD display shows the actual line voltage and fault codes, so a field tech can diagnose without a laptop.