What the 5TT5031-8 is and what it does
The Siemens 5TT5031-8 is a SENTRON Insta contactor — a compact, DIN-rail-mounted switching device for lighting and resistive loads in commercial and residential panelboards. It carries 3 normally-open and 1 normally-closed contact, rated for 25 A operational current at 400 V AC. The coil accepts both 24 V DC and 24 V AC control voltage, making it flexible for building-management or industrial control circuits.
Key ratings and what they mean for fit
The 25 A rating at 400 V AC is the continuous current the main contacts can carry in AC-1 duty (resistive loads like lighting or heating). That is the figure to match against your load current — do not derate it for motor starting unless you know the AC-3 rating separately. The 24 V coil means it drops into standard 24 V control systems common in industrial panels; the AC coil variant also accepts 24 V AC from a building-control transformer. The contactor occupies 2 modular width units (MW) on a DIN rail — 35 mm wide — and has an installation depth of 64 mm (overall depth 71 mm). The IP20 enclosure is suitable for dry indoor panels; no washdown rating. The manufacturer notes that spacers are required between units for heat dissipation, so factor that into your rail layout.
Panel integration notes
Snap-on DIN-rail mount, 35 mm width, 2 MW. The 64 mm installation depth fits standard 80 mm deep enclosures. Wire the 3 NO contacts for load switching; the single NC contact can serve as a feedback or auxiliary signal. The 24 V coil is polarity-sensitive only if using DC — verify free-wheel diode polarity if driving from a PLC output with inductive suppression.