Siemens 3RT20281AL24 Contactors
Engineering verification checklist
- Confirm coil voltage matches control circuit nominal (230VAC). The must-operate threshold is 195.5 VAC.
- Verify load current does not exceed 38 A continuous rating for the target motor or feeder.
- Check contact configuration: this unit provides 3PST-NO main poles plus 2NO/2NC auxiliary contacts per title.
- Confirm mounting: chassis or DIN rail compatible per chassis mount specification.
- Validate operate time of 40 ms is acceptable for the circuit's timing constraints.
- Confirm enclosure ambient stays within 25°C to 60°C operating range; do not assume derating if ambient approaches upper limit.
- Verify coil power draw of 79VA does not overload the supplying control transformer or supply.
- For applications requiring specific agency ratings (UL, CSA, IEC), confirm those certifications apply to the installed configuration.
Contact selection parameters
| Parameter | Value |
|---|---|
| Rated current | 38 A |
| Contact form | 3PST-NO (3 Form A) |
| Auxiliary contacts | 2NO/2NC |
| Must-operate voltage | 195.5 VAC |
| Coil power | 79 VA |
| Operate time | 40 ms |
| Operating temperature | 25°C – 60°C |
The 3RT20281AL24 is an S0-frame AC contactor from Siemens, drawing 79 VA at 230 VAC coil and delivering 38 A through three normally-open poles. The integrated auxiliary block (2NO/2NC) suits auxiliary interlock or pilot-duty routing without adding separate relay layers. Operate time of 40 ms aligns with common industrial coil pull-in times for this frame size.
Comparable Siemens S0 contactors
Readers must qualify each alternate independently for their specific installation. The table below uses similarity scores derived from catalog parameters; they do not indicate interchangeability.
| MPN | Coil Voltage | Auxiliary | Packaging | Similarity |
|---|---|---|---|---|
| 3RT20281AL24 | 230VAC | 2NO/2NC | Box | — |
| 3RT20281AL243MA0 | 230VAC | 2NO/2NC | Box | 1.00 |
| 3RT20281AL20 | 230VAC | 1NO/1NC | Bulk | 1.00 |
| 3RT20281AN24 | 220VAC | 2NO/2NC | Box | 1.00 |
| 3RT20281AG24 | 110VAC | 2NO/2NC | Box | 1.00 |
| 3RT20281AC24 | 24VAC | 2NO/2NC | Box | 1.00 |
| 3RT20281AU20 | 380VAC | 1NO/1NC | Box | 1.00 |
| 3RT20281AH20 | 48VAC | 1NO/1NC | Box | 1.00 |
| 3RT20281AV04 | 400VAC | 2NO/2NC | Box | 1.00 |
- 3RT20281AL243MA0: Same voltage, same auxiliary count; differs only in trailing suffix (likely special packaging or test option). Near-parametric match.
- 3RT20281AL20: Same 230VAC coil; reduces auxiliary contacts to 1NO/1NC and ships in bulk packaging rather than box.
- 3RT20281AN24: Drops to 220VAC coil; must-operate shifts to 187 VAC accordingly. Otherwise matches 2NO/2NC and box packaging.
- 3RT20281AG24: 110VAC coil option with 2NO/2NC; must-operate 93.5 VAC. Useful for lower-voltage control systems.