Model 6 Motor Control Centers – Instruction Bulletin PDF
80459-641-01, Rev. 09

Section 11-Troubleshooting

DANGER
Hazard of Electric Shock, Explosion, or Arc Flash
  • Apply appropriate personal protective equipment (PPE) and follow safe electrical work practices. See NFPA 70E, NOM-029-STPS-2011, or CSA Z462.
  • This equipment must only be installed and serviced by qualified electrical personnel.
  • Turn off all power supplying this equipment before working on or inside equipment.
  • Always use a properly rated voltage sensing device to confirm power is off.
  • Replace all devices, doors, and covers before turning on power to this equipment.
Failure to follow these instructions will result in death or serious injury.

The following table lists problems encountered with MCCs, their causes, and remedies. This table is of a general nature and covers only the main causes of problems.

Misapplication of a device can result in serious problems; however, rather than list this cause repeatedly below, note that misapplication is a major cause of motor control problems and must always be questioned when a device is not functioning properly.

Actual physical damage or broken parts can usually be quickly located and replaced.

NOTE: Damage caused by water ingress or flood conditions requires replacement of the equipment.
NOTE: Damaged, arc-rated MCCs must be inspected, repaired, and requalified by Schneider Electric Services personnel to maintain the arc containment ratings.

Contact the Schneider Electric Customer Care Center for repair services, replacement parts, or equipment replacement:se.com/us/en/work/support/ , or by calling 888-SQUARED (888-778-2733), Monday–Friday, 8:00 a.m. to 8:00 p.m. ET.

Motor Control Center Troubleshooting Chart

Part Problem Cause Remedy
Contacts Contact Chatter (also see Noisy Magnet)
  1. Poor contact in the control circuit.
  2. Low voltage.
  1. Replace the contact device or use a holding circuit interlock (3-wire control).
  2. Check the coil terminal voltage and voltage dips during starting.
Welding or Freezing
  1. Abnormal inrush of current.
  2. Rapid jogging.
  3. Insufficient tip pressure.
  4. Low voltage which prevents the magnet from sealing.
  5. Foreign matter prevents the contacts from closing.
  6. Short circuit or ground fault.
  1. Check for grounds, shorts, or excessive motor load current, or use larger contactor.
  2. Install a larger device rated for jogging service.
  3. Replace contacts and springs. Check contact carrier for deformation or damage.
  4. Check the coil terminal voltage and voltage dips during starting.
  5. Clean the contacts with an environmentally safe (CFC-free) contact cleaner.
  6. Remove the cause of the event. Ensure that the fuse and circuit breaker sizes are correct.
Short Trip Life or Overheating or Trips
  1. Filing or dressing.
  2. Interrupting excessively high currents.
  3. Excessive jogging.
  4. Weak tip pressure.
  5. Dirt or foreign matter on the contact surface
  6. Short circuit or ground fault.
  7. Loose connection in the power circuit.
  8. Sustained overload.
  1. Do not file the silver tips; rough spots or discoloration do not harm tips or impair their efficiency.
  2. Install a larger device or check for grounds, shorts, or excessive motor currents.
  3. Install a larger device rated for jogging service.
  4. Replace contacts and springs; check the contact carrier for deformation or damage.
  5. Clean contacts with a CFC-free contact cleaner. Reduce the entry of foreign matter into the enclosure.
  6. Remove the cause of the event; ensure that the fuse and circuit breaker sizes are correct.
  7. Clear and tighten the connection.
  8. Check for excessive motor load current or install a larger device.
Coils Open Circuit Mechanical damage. Replace the coil; handle and store replacement coils carefully.
Overheated Coil
  1. Overvoltage or high ambient temperature.
  2. Incorrect coil.
  3. Shorted turns caused by mechanical damage or corrosion.
  4. Undervoltage; magnet will not seal in.
  5. Dirt or rust on the pole faces.
  6. Mechanical obstruction.
  1. Check the coil terminal voltage. It should not exceed 110% of the coil rating.
  2. Install the correct coil.
  3. Replace the coil.
  4. Check the coil terminal voltage. It should be at least 85% of the coil rating.
  5. Clean the pole faces.
  6. With power off, check for free movement of the contact and armature assembly.
Thermal Overload Relays Tripping
  1. Sustained overload.
  2. Loose or corroded connection in the power circuit.
  3. Incorrect thermal units.
  4. Excessive coil voltage.
  1. Check for excessive motor currents or current unbalance; correct cause.
  2. Clean and tighten the connection.
  3. Replace the thermal units with the correct size for the application.
  4. Voltage should not exceed 110% of the coil rating.
Not Tripping
  1. Incorrect thermal units.
  2. Mechanical binding, dirt, corrosion, etc.
  3. Relay previously damaged by a short circuit.
  4. Relay contact welded or not in series with the contactor coil.
  1. Check the thermal unit selection table. Install the proper thermal units.
  2. Replace the relay and thermal units.
  3. Replace the relay and thermal units.
  4. Check circuit for the cause of the event and correct the condition. Replace the contact or the entire relay as necessary.
Motor Logic™ Overload Relays Overload relay trips on start-up (after more than 3 seconds).
  1. Load is too heavy for motor horsepower.
  2. Wrong overload trip class selected for application.
  3. Incorrect overload FLA setting.
  4. Use of electronic DC injection brake.
  1. Remove excessive motor load or resize motor.
  2. Use Trip Class 20 overload relay instead of Trip Class 10.
  3. Set FLA adjustment according to motor full-load current.
  4. Do not use electronic DC injection brakes with solid-state overload relay.
Overload relay trips on start-up (in less than 3 seconds).
  1. Motor branch circuit fuse blown.
  2. Loose motor branch circuit.
  3. Motor circuit is not 3-phase.
  4. Voltage unbalance on feeder.
  5. Motor winding damage in one or more windings.
  6. Phase loss in primary of wye-delta or delta-wye transformer.
  7. One or more load lead(s) is not routed through relay window or is routed in opposite direction.
  8. Number of load lead passes are different.
  1. Replace blown motor branch circuit fuse(s).
  2. Tighten motor branch circuit connection.
  3. Select different type of overload relay for non 3-phase applications.
  4. Correct voltage unbalance in feeder.
  5. Check motor winding impedance. Rewind if necessary.
  6. Replace blown fuses or tighten connections.
  7. Pass each load lead through its respective window in the same direction.
  8. Each load lead must be looped the same number of passes.
Overload relay trips while running normally.
  1. Load is too heavy for motor horsepower.
  2. Incorrect overload FLA setting.
  3. Use of electronic DC injection brake.
  4. Incorrect overload FLA setting. (Multiple pass applications.)
  1. Remove excessive motor load or resize motor.
  2. Set FLA adjustment according to motor full-load current.
  3. Do not use electronic DC injection brakes with solid-state overload relay.
  4. Recalculate FLA adjustment and set according to motor full-load current and number of looped passes.
TeSys™ T Motor Controller Minor internal detected errors Invalid configuration Indicates either a bad checksum or good checksum but bad data (Invalid configuraion). Both caused by hardware misoperation. Take the following steps:
  1. Cycle power and wait 30 s.
  2. Reset the configuration settings to factory settings.
  3. If the condition persists, replace the TeSys T motor controller.
Configuration checksum (EEROM) incorrect
Loss of internal network communications These messages indicate a hardware misoperation. Take the following steps:
  1. Cycle power and wait 30 s.
  2. If the condition persists, replace the TeSys T motor controller.
A/D out of range
Diagnostic Start command check Check the following:
  • relay outputs
  • all wiring, including:

    • control wiring circuit, including all electromechanical devices

    • power wiring circuit, including all components

    • load CT wiring.

After all checks are complete:
  1. Perform a reset.
  2. If the condition persists, cycle power and wait 30 s.
  3. If the condition still persists, replace the TeSys T motor controller.
Stop command check
Stop check back
Run check back
Wiring/configuration CT reversal Correct the polarity of the CTs. Be sure that:
  • all external CTs face the same direction
  • all load CT wiring passes through windows in the same direction
After all checks are complete:
  1. Perform a reset.
  2. If the condition persists, cycle power and wait 30 s.
  3. If the condition still persists, replace the TeSys T motor controller.
TeSys™ T Motor Controller Wiring/configuration errors Current/voltage phase reversal Check:
  • L1, L2 and L3 wiring connection to be sure wires are not crossed
  • Motor Phases Sequence parameter setting (ABC versus ACB)
After all checks are complete:
  1. Perform a reset.
  2. If the condition persists, cycle power and wait 30 s.
  3. If the condition still persists, replace the TeSys T motor controller.
Phase configuration incorrect
PTC connection
Check for:
  • short circuit or open circuit in the motor temp sensor wiring
  • wrong type of motor temp sensing device
  • improper configuration of parameters for selected device
After all checks are complete:
  1. Perform a reset.
  2. If the condition persists, cycle power and wait 30 s.
  3. If the condition still persists, replace the TeSys T motor controller.
Voltage phase loss Check for:
  • improper wiring, such as loose terminations
  • blown fuse
  • cut wire
  • single-phase motor configured for 3-phase operation
  • Single phase motor not wired through both A and C load CT windows
  • Loss of power source (for example, utility power outage)
After all checks are complete:
  1. Perform a reset.
  2. If the condition persists, cycle power and wait 30 s.
  3. If the condition still persists, replace the TeSys T motor controller.
Magnetic And Mechanical Parts Noisy Magnet
  1. Broken shading coil.
  2. Dirt or rust on magnet faces.
  3. Low voltage.
  1. Replace the magnet and armature.
  2. Clean the magnet with a clean, dry cloth.
  3. Check the coil terminal voltage and voltage dips during starting.
Does Not Pick Up and Seal
  1. No control voltage.
  2. Low voltage.
  3. Mechanical obstruction.
  4. Open or overheated coil.
  5. Wrong coil.
  1. Check the control circuit wiring for a loose connection or poor contact continuity.
  2. Check for the proper coil terminal voltage and voltage dips during starting.
  3. With the power off, check for free movement of the contact and armature assembly.
  4. Replace the coil.
  5. Replace the coil.
Does Not Drop Out
  1. Gummy substance on the pole faces.
  2. Voltage not removed.
  3. Worn or corroded parts causing binding.
  4. Residual magnetism due to the lack of an air gap in the magnet path.
  5. Welded contacts.
  1. Clean the pole faces with a clean, dry cloth.
  2. Check the coil terminal voltage and the control circuit.
  3. Replace the parts.
  4. Replace the magnet and armature.
  5. See Contacts—Welding or Freezing
Pneumatic Timers Erratic Timing Foreign matter in the valve. Replace the complete timing head, or return the timer to the factory for repair and adjustment.
  Contacts Do Not Operate
  1. Maladjustment of the actuating screw.
  2. Worn or broken parts in the snap switch.
  1. Adjust according to the instructions in the service bulletin.
  2. Replace the snap switch.
Limit Switches Broken Parts Over-travel of the actuator. Use a resilient actuator, or operate within the tolerance of the device.
Manual Starters Does Not Reset Latching mechanism worn or broken. Replace the starter.
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