The Siemens 3RU1126-1FD0 is a SIRIUS thermal overload relay, Class 10, size S0, contactor mounting.
Mounts directly onto a SIRIUS S0 contactor — no DIN rail required for the relay itself, though the contactor typically clips onto one. The main circuit uses screw-type terminals, accepting solid 2x (0.5... 2.5 mm²) or AWG equivalents. The relay occupies the same 45 mm width as the S0 contactor, so your panel layout stays predictable. The ATEX certification (DMT 98 ATEX G 001) confirms it's approved for use in potentially explosive atmospheres — check your zone classification against the certificate.
Key ratings in context
Power dissipation runs 6.6 W total (2.2 W per pole) in hot operating state — modest enough that you don't need special ventilation in a typical enclosure, but worth checking if you're packing many relays into a small cabinet.