47
Instructional Book
MN01301003E
Effective July 2011
Series NRX Low Voltage Power (Air)
Circuit Breakers User Manual
EATON CORPORATION
www.eaton.com
Section 7: Troubleshooting
Introduction
Table 7
will help to determine the probable causes of simple circuit
breaker problems and possible corrective actions. Possible problems
associated with the electronic trip unit are covered in a companion
publication, IL01301051E (Digitrip 520) or IL01301064E (Digitrip 1150).
If the problem cannot be resolved with the aid of one or both of these
guides, contact the Eaton service center for more in-depth assistance.
Table 7. Circuit Breaker Troubleshooting Guide
Symptom
Probable Cause
Corrective Action
The circuit breaker trips open (red fault trip
indicator button is out and/or fault indicator LED
is lighted) when closed on a load current
Rating plug not installed and load current through the
breaker
Install appropriate rating plug compatible with frame rating module
Repeated closing on transient (in-rush) current with thermal
memory active
Wait for circuit breaker (and loads) to cool before reclosing
An overload or fault current condition
Use status and fault indicators to help locate and remove overload or fault
condition
Circuit breaker opens (fault trip indicator button is
not out)
Undervoltage release operates; voltage too low or zero
Check and correct the UVR supply voltage (85–110% rated voltage)
Shunt trip opens
Check control signal(s) to shunt trip; correct if necessary
Trip latch is defective
Inspect latch condition and engagement before closing; consult Eaton
Circuit breaker cannot be opened remotely, but can
be opened locally
Shunt trip control signal absent or too low
Check supply voltage exceeds 70% of rated voltage when signal is applied to
shunt trip
Shunt trip is faulty or improperly installed
Check voltage supplied to shunt trip; make sure ST is seated in its tray; check
for ST motion; replace ST if faulty
Secondary wiring problem
Make sure electrical connections are properly made and verify proper wiring
Circuit breaker cannot be opened locally
OPEN pushbutton locked
Remove lock
Faulty mechanism or main contacts welded
Contact Eaton
Circuit breaker makes no attempt to close with either
local (manual) or remote controls; springs do
not discharge
Closing spring not fully charged (check SPRING CHARGED
indicator)
Charge spring manually; check voltage to electrical operator; replace operator
if faulty
If equipped with undervoltage release, undervoltage
release is not energized or is faulty
Remove left accessory tray containing UVR and retry closing operation; if OK,
check voltage supply to UVR (>85%); replace UVR if faulty
Circuit breaker locked in OPEN position
Check reason for lock
Drawout position interlock is operating; levering screw
Make sure circuit breaker is at a position that permits closure; check that
shutter door over levering screw is fully closed
Circuit breaker interlocked with another circuit breaker or
device
Check for presence of an interlocking scheme (cable or key); check to see if
interlocked circuit breaker is CLOSED
Circuit breaker can’t be closed remotely (can be
closed locally)
Spring release (closing) coil supply voltage low or SR faulty
Check power supply voltage; replace spring release if faulty
Secondary contact wiring problem
Make sure electrical connections are properly made and verify proper wiring
Spring release closing coil signal blocked
Clear Digitrip 1150 relay contact
Circuit breaker can’t be closed locally (can be closed
remotely)
Opening and/or closing pushbuttons locked
Check reason for lock
Circuit breaker does not recharge electrically but will
recharge manually
Charging motor supply voltage absent or too low (<85%)
Check charging motor electrical circuit voltage (under load)
Charging motor faulty
Replace motor assembly
Drawout circuit breaker will not lever in
Cell rejection code plate
Breaker rating not compatible with cassette requirement
Levering-in screw not fully in DISCONNECT position at
insertion
Rotate levering handle counterclockwise to DISCONNECT position,
then insert circuit breaker fully into cassette
Circuit breaker not pushed into cassette far enough
Push circuit breaker in as far as possible
Protective shutters jammed/locked
Position detent is engaged
Clear problem
Reset detent system
General