The Siemens 3RF3320-1DA02 is a SIRIUS 3RF33 series solid-state contactor, 1-pole, rated AC-1 / 20 A at 40 °C. It accepts a universal control voltage of 24-230 V AC/DC, and specifically 24 V DC for the logic input. The contactor is designed as short-circuit-proof when paired with a B-curve miniature circuit breaker, and terminates via screw terminals.
The AC-1 / 20 A rating at 40 °C means this contactor handles resistive loads — heaters, incandescent lighting, resistive banks — up to 20 A continuous without derating at typical panel ambient. If you're switching motor loads (AC-3 duty), you'll need to derate significantly; this is a 1-pole device, so single-phase resistive switching is its sweet spot. The universal control voltage (24-230 V UC) covers both AC and DC control circuits. The 24 V DC low end pulls in reliably on a standard 24 VDC PLC output without a dropping resistor. Short-circuit-proof with B-curve MCB means you don't need a separate upstream fuse for semiconductor protection — the B-curve breaker's fast trip characteristic limits let-through energy below the thyristor's I²t rating. Saves a fuse holder and a line item on the BOM.
Compliance and shipping reality
RoHS compliant since 15-Jan-2024, with a REACH Article 33 notification for Lead (CAS 7439-92-1) above 0.1% w/w in one or more homogenous materials. Packaging dimensions are 105 x 27 x 122 mm, single unit.