110 A AC-1, 4-pole, 12 V DC coil
The Siemens 3RT2344-1BA40 is a SIRIUS contactor rated 110 A in AC-1 duty at 400 V and 40 °C ambient — that resistive-load rating is the one to use for heater banks, lighting, or transformer primary switching, not the motor-breaking AC-3 figure. Four main poles with a 690 V rated insulation voltage (pollution degree 3) and an 8 kV rated impulse withstand voltage on the main circuit — this covers 400 V line-to-line switching with solid margin for transient spikes. Coil is 12 V DC with screw-type terminals; the integrated varistor snubs the back-EMF on dropout, so you can drive it from a PLC digital output without an external flyback diode.
Auxiliary contacts and wire termination
Built-in 1 NO + 1 NC auxiliary contacts with screw terminals — enough for a seal-in circuit and a status feedback without bolting on an extra block. Drop-out time on DC is 38 to 57 ms — that window matters if your safety circuit relies on the NC mirror contact opening fast enough to catch a fault before the next scan.
Clearance and mounting
Up to two auxiliary switch blocks can be attached on the front — the contactor ships with the base 1 NO+1 NC, but you can stack additional blocks without losing the side clearance.
The SIRIUS line is Siemens' standard contactor family, so BOM continuity is stable for new builds and MRO spares.