The Siemens SIRIUS 3RH2244-1BB40 is a 4-pole auxiliary contactor, size S00, with 4 normally open (NO) instantaneous contacts and a 24 VDC coil. Coil pickup and holding are both rated at 4 W DC, so the control transformer sizing is straightforward — no inrush spike to budget for. The coil holds at 24 V nominal; the 0.8 initial-to-full-scale ratio means it pulls in reliably even if the DC supply sags a bit.
What the contact ratings mean for your load
Each NO contact is rated for specific voltages: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V, 1 A at 690 V. These are the thermal / utilization category ratings — use them as the hard ceiling for switching resistive or lightly inductive control loads. For DC switching, the arcing time runs 10–15 ms, so inductive DC loads need proper flyback suppression to avoid contact welding. The 4 NO contacts are all the same rating, so you can parallel them for higher current on a single signal (up to 40 A total at 24 V, but watch the terminal capacity — 2x 2.5 mm² per terminal is the practical limit).
Width is 45 mm, depth 117 mm, height 57.5 mm — it's a standard S00 footprint that snaps onto 35 mm DIN rail or screws directly to a backplate. That means you can orient it to fit tight enclosures without derating. That's less than many contactors — useful when packing auxiliaries next to the main contactor in a crowded panel.
The SIRIUS family is broad, and the 3RH2 series covers auxiliary contactors with various contact configurations and coil voltages. The 3RH2244-1BB40 is the 4 NO, 24 VDC variant. If your panel was spec'd around a 3RT2028-1BB40 power contactor, this auxiliary sits alongside it on the same DIN rail, same S00 footprint — no rewiring needed for the mounting.
Relative humidity minimum is 10 %, so it handles dry climates without issue. RoHS compliance date is October 1, 2009 — it's been RoHS-compliant for over a decade. No substance prohibitance issues for current builds.