Siemens 3RT20231FB40 Size S0 Contactor
Overview
In a motor-branch control cabinet, the 3RT20231FB40 combines main power contacts and auxiliary contacts in a single Size S0 device for DC coil control circuits. This Siemens SIRUS 3RT2 series contactor carries a 9 A contact rating with a 24 VDC coil drawing 245.8 mA at pick-up and dissipating 5.9 W when energized.
Key Specifications
| Parameter | Value |
|---|---|
| Coil Voltage | 24 VDC |
| Coil Current (typical) | 245.8 mA |
| Coil Power | 5.9 W |
| Coil Resistance | 97.6 Ω |
| Must Operate Voltage | 19.2 VDC |
| Contact Rating (main) | 9 A |
| Contact Form | 3PST-NO (3 Form A) |
| Auxiliary Contacts | 1 NO + 1 NC |
| Mounting | Chassis mount, DIN rail |
| Encapsulation | Bulk |
The must-operate voltage of 19.2 VDC defines the minimum coil voltage required to guarantee contact closure. The 24 VDC coil is designed to pull in reliably at roughly 80% of nominal supply—a common threshold in industrial 24 VDC control systems.
Engineering Verification Checklist
- Control circuit supply is 24 VDC; verify nominal voltage and ripple specifications at the coil terminals
- Confirm must-operate voltage of 19.2 VDC is satisfied under worst-case supply conditions
- Verify auxiliary contact configuration (1 NO + 1 NC) matches the schematic requirement for the specific control function
- Confirm the 9 A contact rating is appropriate for the intended load type and coordination requirements
- Verify DIN rail or chassis mounting provisions are compatible with the physical installation envelope
- Check that coil power dissipation of 5.9 W will not cause thermal concern in enclosed panels
- Confirm unit quantity and packaging form (bulk) meet procurement and storage requirements
- Verify the main contact arrangement (3PST-NO) is suitable for the motor or resistive load being switched
Similar Catalog Parts
The following parts share the same base product number (3RT2023) and fall within the same Siemens SIRUS 3RT2 Size S0 family. Similarity scores reflect catalog-level parametric overlap; all candidates require the reader's own qualification against the specific application.
| MPN | Coil Voltage | Coil Power | Aux Contacts | Encapsulation | Similarity |
|---|---|---|---|---|---|
| 3RT20231FB40 (primary) | 24 VDC | 5.9 W | 1NO/1NC | Bulk | — |
| 3RT20231FB443MA0 | 24 VDC | 5.9 W | 2NO/2NC | Box | 1.0 |
| 3RT20231BB40 | 24 VDC | 5.9 W | 1NO/1NC | Bulk | 1.0 |
| 3RT20231DB40 | 24 VDC | 5.9 W | 1NO/1NC | Box | 1.0 |
| 3RT20231KB40 | 24 VDC | 4.5 W | 1NO/1NC | Box | 1.0 |
3RT20231FB443MA0 differs primarily in auxiliary contact count: two NO and two NC (2NO/2NC) versus the primary's 1NO/1NC. This variant suits applications requiring more auxiliary contacts for indication or interlock circuits. Box encapsulation is standard versus bulk.
3RT20231BB40 shares the same bulk encapsulation and 1NO/1NC auxiliary arrangement. Operating temperature range appears as 25°C ~ 60°C in the catalog record—otherwise identical coil and contact ratings.
3RT20231DB40 matches on coil voltage, power, contact rating, and auxiliary configuration but specifies an operate time of 170 ms and uses box encapsulation.
3RT20231KB40 shares the same 1NO/1NC configuration and nominal 24 VDC coil but lists a lower coil power of 4.5 W and a lower must-operate voltage of 16.8 VDC, indicating a different coil class within the same frame size.