What it is and where it fits
The Siemens SIRIUS 3RT2037-1AF00-ZX95 is a Size S2 power contactor, the core switching element for motor loads in a control panel. It mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 60715, which is the standard rail in most industrial enclosures. The S2 frame size tells you it handles the mid-range of the SIRIUS contactor family — above the S0, below the S3 — and the 65 A rating at 480 V AC-3 means it's sized for a 30–40 hp motor on a 480 V line, typical for pumps, fans, or conveyors in a 480 V plant. The -ZX95 suffix is a Siemens special version code — it doesn't change the electrical ratings, but it flags a specific variant (often a customer-specific or custom-logged build). The base contactor carries an auxiliary switch as standard, with coil terminals as screw-type. Wire acceptance is 2x 0.5–1.5 mm² or 2x 0.75–2.5 mm² solid/stranded, which covers most panel wiring up to 12 AWG.
Key ratings and what they mean for fit
The headline number is 65 A at 480 V — that's the AC-3 (motor starting) rating. AC-3 means switching a squirrel-cage motor: high inrush on make, lower current on break. For resistive loads (AC-1), the contactor can cycle more often — 800 ops/hour — but the AC-3 duty cycle of 700 ops/hour is the one that governs motor switching. The AC-4 rating (plugging/reversing) drops to 200 ops/hour, so if your application does frequent inching or reversing, derate the switching rate accordingly. The auxiliary contacts are rated across a range of voltages: 10 A at 24 V, 2 A at 48 V and 60 V, 1 A at 110 V, 0.9 A at 125 V, 0.3 A at 220 V, 3 A at 400 V, 0.6 A at 440 V, and 2 A at 500 V. That covers standard control voltages in both 24 VDC and 120/240 VAC control circuits. The 10 hp rating at 230 V gives a quick rule-of-thumb for 230 V single-phase motor loads. Mechanical life is typical 10 million operations. Arcing time is 10–20 ms, and operate time at AC is 10–18 ms. These are fast enough for most motor control circuits; the contactor closes and opens cleanly within a half-cycle of 50/60 Hz.
Mounting and clearances
Physical footprint: 114 mm high, 55 mm wide, 130 mm deep. That's the body dimensions; you need clearance for arc chutes and wiring. Required free space: 10 mm upwards, 10 mm forwards, 10 mm downwards, and 6 mm to the side. On a 35 mm DIN rail, the S2 width of 55 mm means it occupies about 3.1 standard 18 mm module spaces — plan your rail layout accordingly. Mounting position is flexible: +/-180° rotation on a vertical surface, and can be tilted forward/backward by +/-22.5° on a vertical surface. That covers most panel orientations, including horizontal rails in a vertical enclosure. Operating temperature range is -25 to +60 °C; storage range is -55 to +80 °C. The storage range is wider — that's the handling/shipping limit, not the running limit.