What it is and what it does
The Siemens 5TT5810-0 is a SENTRON insta contactor with two normally-open contacts, rated for 230 V AC coil voltage and switching 400 V at 25 A. It's a compact panel-mount contactor for resistive or moderate inductive loads — think lighting banks, heater circuits, or small motor contactor duty where a 2-pole make is enough.
Panel fit and installation
18 mm wide (one modular width unit) and 71 mm deep — it snaps onto DIN rail and leaves the same 90 mm height as the rest of the SENTRON modular range. The spec calls out spacers for heat dissipation, so don't pack it tight against other heat sources without the recommended air gap. IP20 means it's protected against solid objects larger than 12.5 mm but not against moisture — keep it inside the enclosure, away from washdown zones.
What the ratings mean for your BOM
The 230 V AC coil means it pulls in on a standard line-voltage control circuit — no separate 24 V DC supply needed. The 400 V 25 A switching capacity covers most single-phase lighting or small three-phase loads; derate for inductive or incandescent inrush (the 1 000 W incandescent lamp rating gives a reference for that duty). Power loss is 2 W per pole in hot state — negligible for panel thermal budgeting, but factor it if you're stacking several contactors in a sealed enclosure.