Siemens 3RT20171AD02 Electromechanical Contactor

The Siemens 3RT series denotes a.Size S00 contactor family, and the 3RT20171AD02 specifically represents a 42VAC coil variant with one normally-open (1NO) auxiliary contact alongside three main power poles. The device is packaged for chassis and DIN rail mounting, enclosing a box-configuration relay with auxiliary contact features and a 12A current rating.

Contact ratings and switching thresholds

• Main pole configuration: 3PST-NO (3 Form A) — three independent NO contacts for motor or load branch switching.
• Continuous current rating: 12 A per pole.
• Must-Operate Voltage: 35.7 VAC — coil must receive at least this level to ensure pull-in.
• Coil data: 42VAC nominal coil voltage, 33VA inrush/sealed power draw.
• Operate/Release timing: 35 ms operate; release time appears consistent within the series.

Physical and environmental parameters

• Operating temperature range: 25°C ~ 60°C.
• Mounting type: Chassis mount with DIN rail adapter support.
• Encapsulation: Box packaged unit.
• Contact form summary: The primary poles are 3PST-NO; the auxiliary section carries 1NC (one normally closed auxiliary contact noted in the title suffix — verify exact aux configuration against the plant single-line drawing before committing to panel layout).

Catalog peer comparison (selection screening only)

• 3RT20171AD01: Same coil voltage and current rating, but the auxiliary contact configuration swaps NC for NO — critical when the control circuit expects a specific aux state.
• 3RT20171AH02: 48VAC coil — sits near the 42VAC class; suitable when control-system nominal is 48VAC rather than 42VAC; the must-operate threshold shifts to 40.8 VAC.
• 3RT20171AB02: 24VAC coil variant (20.4 VAC must-operate) — useful for reduced-voltage control circuits or low-voltage SELV control; coil power differential noted in series (37VA vs 33VA).

Key selection trade-offs within the 3RT2017 series

1. Coil voltage selection drives panel-level coordination: the 42VAC model (3RT20171AD02) requires a 35.7 VAC must-operate threshold — ensure upstream control transformers or PLC outputs match or exceed this.
2. Auxiliary contact polarity (NO vs NC) governs feedback or interlock wiring: the seed carries one NC auxiliary; switching to a 1NO variant (e.g., 3RT20171AD01) reverses logic in the feedback path.
3. Current class differs across voltage coil variants: higher coil voltage variants may carry adjusted continuous-current capability — check the specific order-code rating against branch coordination requirements.
4. DIN mount vs chassis-only orientation: all listed variants support DIN rail clip attachment, but mechanical enclosure depth clearance should be verified independently for the 42VAC coil model.
5. Operating temperature ceiling is 60°C: when mounted in enclosed panels near motor starters or drive blocks, thermal margins should be assessed against actual panel ambient.

FAQ

What distinguishes the 3RT20171AD02 from other variants in the 3RT2017 family? It carries a 42VAC control coil, 12A main poles in 3PST-NO arrangement, and one NC auxiliary contact. The must-operate threshold sits at 35.7 VAC, differentiating it from 24VAC (20.4 VAC) and 48VAC (40.8 VAC) counterparts within the same base series.

Can the auxiliary contact configuration be substituted by a NO variant? Functionally, yes — but the NC → NO polarity change alters interlocks, feedback, or seal-in logic. Selection depends on whether the control circuit requires a normally-closed or normally-open state under de-energized coil conditions.

Is the 12A rating consistent across all coil voltage options in this series? The 12A rating appears on both the 42VAC and 48VAC variants. Other coil voltages (e.g., 230VAC) may carry different current ratings — verify against the specific order-code listing before applying to higher-load branches.