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Eaton XTOB vs XTOT Overload Relays: Current Range & Trip Class
Motor control · Selection guide
Understand the difference between bimetallic and current-transformer-operated overload relays, then select the current range, trip class, mounting and control contacts for the motor application.
Eaton’s XT overload relay range is used to protect motors against sustained overload. The XTOB and XTOT designations identify different sensing arrangements, so the full model code matters as much as the current setting.
- XTOB identifies a bimetallic overload relay.
- XTOT identifies a current-transformer-operated overload relay.
- Verify trip class, reset mode, phase-failure behavior and accessory compatibility by part number.
Official Eaton product image · XTOB family · View product details
Quick answer:In this guide- XTOB and XTOT compared
- Current range and trip class
- Phase-failure protection
- Auxiliary contacts and control circuit
- Selection checklist
- FAQ
1. XTOB and XTOT: what is the difference?
| Designation | Sensing principle | Typical use | What to verify |
|---|---|---|---|
| XTOB | Bimetallic thermal overload relay | Direct mounting to a compatible XT contactor or separate mounting, depending on model. | Motor current setting range, frame, trip class, reset and permitted contactor combination. |
| XTOT | Current-transformer-operated overload relay | Higher-current applications where the CT-operated arrangement is specified. | CT/relay rating, selected current range, trip class and wiring requirements. |
The family code helps identify the operating principle, but it does not establish the exact overload range or the complete motor-protection performance. Use the current Eaton catalog selection table for the full part number.
2. Match the motor current and trip class
Eaton catalog literature describes XTOB thermal overload relays for direct connection up to 250 A and the broader XT overload-relay line for applications extending higher, including CT-operated types. Published overview material may state a family-level maximum that differs from individual catalog selection tables; the exact part number and current regional catalogue are controlling.
| Selection item | What it means | Practical check |
|---|---|---|
| Overload range | The adjustable current band of the selected relay. | Motor nameplate current must fit the exact model’s setting range. |
| Trip class | Defines the relay’s overload response characteristics. | Eaton catalog codes distinguish Class 10A and Class 30 variants; verify the code on the selected model. |
| Mounting | Direct-to-contactor or separate mounting, depending on version. | Confirm contactor frame, mounting base and terminal accessories. |
| Reset mode | Manual or automatic reset, depending on model. | Choose based on the machine’s restart risk assessment and control design. |
The original source table mixed current ranges, relay type and sensing principle in several rows. Those row-level values have therefore not been presented as a verified part-number matrix; confirm them against the current Eaton catalog before publication or ordering.
3. Phase-failure behavior: check the exact model
Phase-loss protection is an important motor-protection requirement, but it should not be inferred solely from the word “thermal” or “CT-operated.” Confirm that the selected relay’s datasheet explicitly documents the required phase-failure sensitivity and operating behavior for the intended motor and starter arrangement.
- Review the manufacturer's functional description and trip characteristics.
- Check the application’s overload and phase-loss protection requirements.
- Confirm the relay is coordinated with the contactor and short-circuit protective device.
- Use the specified reset mode and test procedure in the installation manual.
4. Auxiliary contacts and the control circuit
The XTO range is offered with auxiliary contact configurations that can be used in a contactor control circuit to signal a trip or interrupt the contactor coil circuit. Check the selected relay’s contact diagram and terminal numbering before wiring. A normally closed contact is often placed in series with the contactor coil in a conventional stop-on-overload arrangement, but the actual circuit must follow the machine’s control and safety design.
Also verify whether the relay mounts directly to the selected contactor or requires a separate base. Frame size, terminal arrangement and mounting hardware are model-specific; accessory family names should not be treated as universal compatibility guarantees.
5. XTO selection checklist
- Record motor nameplate current, voltage, duty and starting conditions.
- Select XTOB or XTOT according to the required relay type and current range.
- Choose a setting range that includes the motor current and confirm trip class.
- Verify documented phase-failure behavior if it is required by the application.
- Check contactor frame, direct/separate mounting, reset mode and auxiliary contacts.
- Validate coordination with the short-circuit protective device using Eaton tables.
Frequently asked questions
Does XTOB mean an electronic overload relay?
No. Eaton’s catalog designates XTOB as a bimetallic overload relay and XTOT as a current-transformer-operated overload relay.
Can I choose a relay based only on its ampere rating?
No. The setting range, trip class, mounting, reset mode, contactor combination and protective coordination all matter.
Does every XTO relay cover the same current range?
No. The range depends on the model and frame. Use the exact catalog number and current Eaton selection table.
Manufacturer referencesCatalog values vary by frame and regional edition. Verify the exact model before design approval or purchase.
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TAG: Eaton XTO XTOB XTOT thermal overload relay CT overload relay motor protection trip class 10A trip class 30