The E300 Electronic Overload Relay (Bulletin 193/592) reports trips and warnings with a Trip/Warn LED that blinks in groups of long and short blinks, and it records the reason in its parameters. Below: how to read the LED, look up the code, read the trip history and reset correctly. Codes, parameters and pages are from the Rockwell Automation E300 user manual,
1. The two LEDs to look at first: Power and Trip/Warn
The E300 communication modules and the Operator Station both have two diagnostic LEDs: Power and Trip/Warn (
| Power LED | Meaning |
|---|---|
| Blinking green | Ready (Ready Mode) |
| Solid green | Running, current detected (Run Mode) |
| Solid red | Device Error |
| Blinking red | Communication error, Operator Station only |
| Blinking green/red | CopyCat in progress, Operator Station only |
The Trip/Warn LED tells you the type of event (p. 209):
- Blinking red = trip. Outputs configured as a Trip Relay open (p. 120).
- Blinking yellow = warning. An alert only, not yet a trip.
The LED blinks a group of long blinks and short blinks. Count both and look them up in section 2. Example: 0 long, 2 short is Phase Loss.
2. Blink codes and common causes
Blink code = long–short (Table 51, pp. 210–211). Trip History = the code written to the trip history (Table 35, pp. 162–163); — means Table 35 has no single matching code (for hardware faults it lists several, for example 55 "Hardware configuration fault"). Causes and checks follow the Trip/Warn LED Troubleshooting table (pp. 212–213) and chapter 5.
| Name in the manual | Blink code | Trip History | Common causes | What to check |
|---|---|---|---|---|
| Overload | 0–1 | 1 | Motor overloaded; wrong parameter settings | Load, mechanical transmission, motor bearings; FLA Setting (171), Trip Class (172) |
| Phase Loss | 0–2 | 2 | Missing supply phase; poor connection; contactor | Blown fuse, tighten terminations from the branch protection to the motor, contactor; Single/Three Phase (176) |
| Ground Fault Current | 0–3 | 3 | Conductor or winding shorted to ground; decayed insulation; foreign object; core balance sensor wired wrong | Insulation resistance; sensor cable |
| Stall | 0–4 | 4 | Motor not at full speed by the end of Stall Enabled Time (249) | Excessive load, failed transmission; 249 set too short; FLA Setting (171) |
| Jam | 0–5 | 5 | Running current above Jam Trip Level (253) | Mechanical jam; 253 set too low; FLA Setting (171) |
| Underload | 0–6 | 6 | Current below normal operating level | Torn conveyor belt, damaged fan blade, broken shaft, worn tool (p. 126) |
| Current Imbalance | 0–7 | 7 | Imbalanced supply; winding imbalance; motor idling; contactor/breaker | Supply, fuses; Current Imbalance Trip Level (261) |
| Under Voltage / Over Voltage | 1–1 / 1–2 | 17 / 18 | Line voltage below or above the trip level | Supply |
| Phase Rotation Mismatch | 1–4 | 20 | Supply phases rotated | Phase sequence |
| Test | 3–1 | 49 | Test/Reset button held for 2 seconds | Press Test/Reset to clear |
| PTC | 3–2 | 50 | Stator windings overheated; thermistor leads shorted or open | Overload, blocked cooling, ambient, starts per hour; thermistor leads |
| Remote Trip | 3–5 | 53 | External sensor contact closed (for example a vibration switch) | Fix the cause, check the sensor and wiring |
| Blocked Start | 3–6 | 54 | Starts per hour reached (205) or Starts Interval (206) not yet elapsed | Read Time to Start (31) and wait, or change the configuration |
| Hardware Fault | 3–7 | — | Sensing module firmware not compatible with control module; hardware configuration failure | Module firmware revisions, pins between modules |
| Configuration | 3–8 | — | Invalid configuration value; parameter 176 set to single phase while current is sensed in L3; no Trip Relay assigned in "Overload (Network)" mode | Read parameters 38 and 39; check 176 and 202…204 |
| Nonvolatile Memory | 3–14 | — | Firmware downgrade corrupted memory; internal failure | Section 6 |
Voltage trips (group 1) exist only with a voltage-sensing module such as
3. Reading Trip Status, Warning Status and the trip history
Parameters can be read on the Diagnostic Station (control module firmware v3.000 or later, p. 25) or the EtherNet/IP module's web server when enabled (p. 175). The full parameter list is a spreadsheet attached to the manual's PDF (Preface, p. 9).
| Parameter | No. | Use |
|---|---|---|
| Percent Thermal Capacity Utilized | 1 | Thermal capacity used (%TCU); 100% gives an overload trip |
| Time to Trip | 2 | Estimated time left to an overload trip; 9,999 s when current is below the trip rating |
| Time to Reset | 3 | Time left until an overload trip can be reset |
| Current / Voltage / Power / Control Trip Status | 4 / 5 / 6 / 7 | Trip bits by group (p. 155) |
| Analog Trip Status | 8 | Analog trip bits (p. 146) |
| Current / Voltage / Power / Control Warning Status | 10 / 11 / 12 / 13 | Warning bits by group (p. 155) |
| Analog Warning Status | 14 | Analog warning bits (p. 146) |
| Device Status 0 | 20 | Bit 0 = trip present, bit 1 = warning present (pp. 120, 156) |
| Invalid Configuration Parameter / Cause | 38 / 39 | Which parameter is invalid and why (p. 32) |
| Trip History 0…4 | 127…131 | Last 5 trips, 0 is the most recent (p. 164) |
| Warning History 0…4 | 133…137 | Last 5 warnings (Table 38, p. 166) |
| Trip Snapshot | 156…162 | Line voltages, kW, kVAR, kVA and PF at the most recent trip (p. 166) |
- The history keeps the last 5 trips and 5 warnings in nonvolatile memory (p. 161).
- The Trip History Masks (139…143) select which trips are logged (p. 164). If a trip is missing from the history, check the mask.
- Trip Snapshot is overwritten at the next trip, including a test trip (p. 166). Record it before you try the Test button.
4. Checks by trip type
Overload (0–1)
- Read %TCU (parameter 1) and Trip Class (172).
- Check the load, the mechanical transmission and the motor bearings (p. 212).
- Compare FLA Setting (171) with the motor nameplate. Outside the USA and Canada, MCR motors are set to the nameplate full-load current; for star-delta, divide the nameplate current by 1.73 (p. 121).
Phase Loss (0–2)
- Look for an open line, for example a blown fuse.
- Tighten every termination from the branch circuit protection to the motor, including the
E300-to-contactor connection. - Inspect the contactor.
- Single-phase applications need Single/Three Phase (176) set to "single phase" (p. 212).
- If it trips during starting, review Phase Loss Inhibit Time (239) and Phase Loss Trip Delay (240) (p. 123).
Configuration Fault (3–8)
Read Invalid Configuration Parameter (38) and Invalid Configuration Cause (39), correct that value, then reset (pp. 32, 212). In the "Overload (Network)" operating mode, one of the Output Assignments (202…204) must be set to "Trip Relay" (p. 212).
Loss of communication
Network loss is not in the Trip/Warn blink table. Look at the MS and NS LEDs on the communication module (pp. 208–209). On EtherNet/IP: NS blinking green means no connection is established, so check the scanner's scan list; NS blinking red means a connection timed out; solid red NS can mean a duplicate IP address. When communication is lost, output relays assigned as Normal or Control go to the state set in the Communication Fault Mode parameters (pp. 36–37).
5. Resetting a trip
A reset does not fix the cause. The manual says to correct the cause before resetting (p. 211). A reset can restart the machine; follow the plant's lockout and permit-to-work rules.
Ways to reset (p. 211):
- Press the blue Trip/Reset button on the communication module.
- Press the Reset button on the Operator Station.
- Set the Trip Reset bit in the Output Assembly over the network.
- Apply a reset signal to a digital input assigned to "Trip Reset" (parameters 196…201, p. 40).
- Set Trip Reset (parameter 163) to 1. This only works once all conditions for the trip have cleared (p. 149).
- Set Overload Reset Mode (parameter 173) to "Automatic" so the E300 resets itself after an overload trip.
An overload trip can only be reset once %TCU (parameter 1) is below Overload Reset Level (parameter 174) (p. 211). Parameter 174 is adjustable from 1 to 100% TCU (p. 122). Read Time to Reset (parameter 3) to see how long to wait. The reset mode in parameter 173 applies to overload and PTC trips (p. 121). In explosive environments the manual requires parameter 173 to be set to Manual (p. 123).
Do not run Clear Command (parameter 165) "Clear History Logs" before you have recorded the history. It sets Trip History and Warning History to zero (p. 153).
6. When it is a hardware problem
- Solid red MS (EtherNet/IP): the power-up diagnostic test failed. Cycle power; if it persists, replace the device (p. 208).
- Hardware Fault (3–7): check that control module and sensing module firmware are compatible and update the control module to v2.0 or later; check that the modules are connected properly and that the pins between the sensing module and control module are not bent (p. 212). Each module has its own firmware (p. 201).
- Nonvolatile Storage Fault (3–14): after a firmware downgrade, run the Clear Command for Operating Statistics, History Logs and % TCU; for an internal failure, consult the factory (p. 212).
7. What to record before calling support
- Trip/Warn LED colour and the number of long and short blinks; the state of the Power, MS and NS LEDs.
- Trip History 0…4, Warning History 0…4 and Trip Snapshot 156…162.
- %TCU (1), and the values of Trip Status 4…8 and Warning Status 10…14.
- FLA Setting (171), Trip Class (172), and parameters 173, 174 and 176.
- Catalog numbers and firmware revisions of the sensing, control and communication modules (see the E300 catalog).
- Whether the motor was starting or running when it tripped, and how it was reset.
Need an engineer on site: request support.
Frequently asked questions
What does a blinking red light on an E300 mean?
A blinking red Trip/Warn LED means the E300 has tripped; blinking yellow is a warning. Count the long and short blinks and look them up in Table 51 of
What should I check when an E300 shows Phase Loss?
Look for an open line such as a blown fuse, tighten the terminations from the branch circuit protection to the motor and the
Why will an E300 not reset after an overload trip?
An overload trip can only be reset once Percent Thermal Capacity Utilized (parameter 1) is below Overload Reset Level (parameter 174) (p. 211). Time to Reset (parameter 3) shows how long you still have to wait.
Where do I find the E300 trip history?
Trip History 0…4 are parameters 127…131, with 0 the most recent trip (p. 164). The codes stored there are listed in Table 35 (pp. 162–163); for example 1 is overload, 2 is phase loss and 3 is ground fault.
Sources
- Rockwell Automation,
193-UM015F-EN-P , E300 Electronic Overload Relay User Manual, 08/2018 — pp. 9, 25, 32, 36–37, 40, 119–126, 129, 143, 146, 149, 153, 155–156, 161–166, 175, 201, 207–213
Read 8 November 2026. This article paraphrases the sources and does not quote them; read the original documents before designing or working on a system.