Siemens 3RU21261EJ0 Thermal Overload Relay
Thermal Overload Relay Positioning
The 3RU21261EJ0 is a SIRIUS thermal overload relay sized for S0 contactor mounting. In a motor branch, it sits between the contactor and the motor feeder, providing Class 10 overload protection by responding to heat generated by excess current flow through its bimetal strips. The catalog entry records an adjustment range of 2.8–4 A and ROHS3 Compliant status.
Key Parameters (3RU21261EJ0)
| Parameter | Value |
|---|---|
| Accessory Type | Thermal Overload Relay |
| Series | SIRIUS |
| Base Product Number | 3RU2126 |
| Current Adjustment Range | 2.8–4 A |
| Encapsulation | Box |
| For Use With | Contactors |
| RoHS | ROHS3 Compliant |
| Product Status | Active |
Catalog Comparison — Adjacent Current Ranges
The following catalog peers share the same SIRIUS 3RU2126 base product number and thermal overload relay type but differ in adjustment range. All require user-side qualification before use.
| Parameter | 3RU21261EJ0 (primary) | 3RU21261EC0 | 3RU21261FJ0 | 3RU21261DJ0 |
|---|---|---|---|---|
| Current Range (A) | 2.8–4 | 2.8–4 | 3.5–5 | 2.2–3.2 |
| Encapsulation | Box | Box | Box | Box |
| Series | SIRIUS | SIRIUS | SIRIUS | SIRIUS |
| For Use With | Contactors | Contactors | Contactors | Contactors |
| Similarity | — | 0.91 | 0.87 | 0.87 |
Why the Alternates Are Catalog-Neighbors
- 3RU21261EC0 carries the same 2.8–4 A band as the primary; the trailing "SP" suffix indicates a separate packaging variant, sharing all other spec anchors and the SIRIUS series family.
- 3RU21261FJ0 steps up to a 3.5–5 A band while holding the same Box encapsulation, thermal overload type, and SIRIUS contactor compatibility.
- 3RU21261DJ0 steps down to 2.2–3.2 A but retains the identical series, base product number, and Box form factor.
Each alternate shares the same mechanical envelope and contactor mounting interface; the selection variable is purely the current calibration window.
Additional Catalog Adjacents (3RU21261GJ0, 3RU21261CJ0, 3RU21261HJ0, 3RU21261JJ0, 3RU21261KJ0)
These parts complete the SIRIUS 3RU2126 thermal overload relay family coverage from 1.8 A through 12.5 A, all in the Box encapsulation and all designed for contactor integration. The adjustment ranges are 1.8–2.5 A, 4.5–6.3 A, 5.5–8 A, 7–10 A, and 9–12.5 A respectively. They share the same accessory type, series, and base product number as the primary part; selection proceeds by matching the motor full-load current to the appropriate band.
FAQ
Q: What motor full-load current range is covered by the 3RU21261EJ0? A: The adjustment dial covers 2.8 A to 4 A. The relay trips thermally at approximately 120% of the dial-set current, consistent with Class 10 timing.
Q: Can the 3RU21261EJ0 mount directly to any SIRIUS contactor? A: The record states the relay is for use with contactors and sized to S0; matching to the specific contactor coil voltage and aux contact configuration requires user-side coordination.
Q: Is the 3RU21261EJ0 ROHS3 compliant? A: Yes; the catalog record lists ROHS3 Compliant status.