The Siemens 5TT5702-2 is an INSTA-series contactor with two normally-closed (NC) main contacts, rated for 20 A at both 230 V AC and 400 V AC, with a 24 V AC coil for activation. That 20 A rating across both common line voltages means it handles resistive or lightly inductive loads like heater banks or lighting circuits without derating between 230 V and 400 V systems — one less variable when you're populating a panel that feeds mixed-voltage zones.
Panel integration
As an INSTA-series contactor, the 5TT5702-2 snaps onto standard DIN rail — the same 35 mm profile used across Siemens panel-building components. The two NC contacts are wired in series with the load; the 24 V AC coil pulls from a control transformer or dedicated AC supply. Keep the coil wiring separate from the power circuit to avoid induced noise on the control side during switching.