Appendix B: Troubleshooting
Symptom
Probable Cause
Possible Solution(s)
References
Unit Status LED is
not blinking
Current through breaker is less than 100A
(single-phase) or 35A (three-phase)
No problem. Status LED will not operate
with breaker currents less than 100A
(single-phase) or 35A (three-phase)
Current is not flowing through the circuit
breaker sensors to the trip unit.
C24 Vdc and ground auxiliary
power to circuit breaker terminals 21 and
22 and observe status LED
Trip unit is malfunctioning
Replace trip unit
Unit Status LED is
steadily on
Light loading
No problem. Status LED will not flash until
above 35A
See Section 5: Principles of operation for
trip and operational indicators
Trip unit is malfunctioning
Replace trip unit
When current starts flowing through the
breaker, it trips. The orange (not red)
instantaneous trip LED lights
Rating plug is not installed or is loose
Install rating plug and/or check for loose
connections
Rating plug is open internally
Replace rating plug
LED does not light when Battery Check
button
is pressed
Battery installed backwards
Install correctly
See Section 9: Trip unit battery
Dead battery
Replace battery
Frame module is malfunctioning
Check with your Eaton representative for
factory assistance
Breaker trips on
ground fault
There actually is a ground fault
Find location of the fault
On three-pole, four-wire residual systems,
the neutral current sensor may not have the
correct ratio or be properly connected
Check connections at terminals 15 and
16. Check that the connections from the
neutral current sensor to the breaker are
not reversed. Check terminal 19 and 20 for
correct programming of jumper
See Section 5: Principles of operation
and Section 6: Programming Settings for
ground fault protection
See
Table 10
High inrush phase currents may cause
fictitious ground pickup momentarily
If zone interlocking function is employed,
connect a jumper from Zout to Zin to
provide some time delay
See Section 6: Programming Settings for
zone interlocking on ground fault systems.
Trip unit is malfunctioning
Replace trip unit
Breaker trips too rapidly on ground fault
or short delay (zone selective interlocking
not used)
Jumper connection is missing on Digitrip
unit
Check jumper connections
Refer to Appendix A: Zone Selective
Interlocking Examples, Note
Trip unit settings are
not correct.
Is I
2
t slope or Flat selected?
Change settings
Verify settings and refer to Time Current
Curve for intended trip time.
Trip unit is malfunctioning
Replace trip unit
Breaker trips too rapidly on long delay
Long Time Memory selected
Turn off Long Time Memory
Refer to Section 6: Programming Settings
for Long Delay Time setting
Trip unit settings are
not correct
Change settings. Long Time Delay setting
is based on 6 × I
r
Primary injection testing pick up and trip
times are not correct
Primary injection current source is not
putting out the correct current
Use an oscilloscope with a current probe
to accurately verify current values, times
and that there are no inrush spikes of
current observed.
Single phase testing
When testing single phase the current can
“bleed” into other un-energized phases
and reduce the value of current in the
testing phase.
It is possible when using high current
“pulse” testing technique to create a
long time memory trip as a result of the
cumulative action of the short duration
currents.
Disable the Long Time Memory feature
Refer to Section 6: Programming Settings
for Long Delay Time setting
Precise pickup levels are hard to control and
repeat for primary injection testers at high
current levels
Use a secondary injection test kit
Effective September 2013
Instructional Leaflet IL01301064E
Operating Manual for Series NRX
Digitrip Trip Units 1150 / 1150i
40
EATON
www.eaton.com
