SITOP lite, 24 V at 2.5 A — what the headline ratings decide
Siemens 6EP3321-6SB00-0AY0 is a DIN-rail switch-mode power supply in the SITOP lite line, delivering 24 V at a rated 1.9 A with a maximum 2.5 A ceiling; the 2.5 A figure is the short-term headroom, and the continuous 1.9 A number is the one that drives the load calculation on the panel drawing. Above +55 °C ambient the output derates 2 % per kelvin, so a cabinet above the rated temperature loses 0.05 A per degree — sizing matters for sealed enclosures and machine-side cabinets with no active ventilation. Operation is rated -25... +70 °C with natural convection, meaning no fan service interval to plan around; storage and transport envelope extends to -40... +85 °C for spares staged in unconditioned stockrooms.
Wide-range input and the weak-grid margin
AC input covers 100... 240 V rated, full-scale 85... 264 V, with DC input 110... 300 V for battery-backed or DC-bus-fed cabinets — the 85 V lower bound keeps the PSU running through brownout events that would drop lesser supplies. Line frequency is 47... 63 Hz rated at 50 Hz / 60 Hz, so the unit tolerates portable generator sets and shipboard 60 Hz mains without reconfiguration. Internal fusing is fitted; upstream protection calls for a 6 A characteristic B or 2 A characteristic C miniature circuit breaker in the feeder.
Output wiring and terminal envelope
Output is safety extra-low voltage per EN 60950-1 and EN 50178 and is NEC Class 2 compliant — the rating limit that lets the 24 V rail land directly on Class 2 field devices without an extra isolating barrier.
Panel clearance, stacking, and reliability budget
Snap-on fastening to DIN rail EN 60715 35x7.5/15 is supported, with direct mounting in different mounting positions — clearance envelope is 20 mm top and bottom, 0 mm left and right, so adjacent SITOP units can be butted side-by-side without thermal penalty. MTBF is 2 938 542 h at 40 °C — the figure panel builders carry into the reliability block of the project FMEA; I²t maximum is 0.8 A²·s, the inrush budget the upstream breaker characteristic must accommodate.
Approvals — where the supply lands without paperwork fights
The unit carries CE marking, EAC approval, and DNV GL marine approval — panel builders specifying into shipboard or EAC-supervised cabinets do not need a separate deviation request. ATEX, IECEx, FM, and UL hazloc approvals are not on the listing — for Zone-classified or hazardous-location cabinets a different SITOP variant is required, not this part number.
Sourcing posture
Lifecycle status reads current, so independent distribution quotes against the BOM; lead time, package quantity, and volume pricing are confirmed at RFQ — no stockholding or immediacy claim is made on the page.