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 TM 5-684/NAVFAC MO-200/AFJMAN 32-1082
Table 8-2. Troubleshooting chart for power circuit breakers
Remedy
Cause
Trouble
--
Overheating
Poor condition of contacts:
(1) Contacts should be lined up and adjusted
(1) Out of proper alignment and adjustment.
properly.
(2) Burned and pitted contacts should be
(2) Burned and pitted because of lack of at-
dressed up, if practical, or replaced with new
tention after many heavy operations, or too
parts. (High-pressure butt-type contacts usu-
frequent operation.
ally do not require dressing. Silver-to-silver
contacts should be dressed very carefully and
only when actually required.))
(3)) Circuit breaker kept closed (or open) for
(3) Operate circuit breaker more frequently to
wipe contacts clean. It may be advisable to
too long a period (copper contacts).
consider the installation of new silver-to-silver
contacts. The nearest manufacturer's
should be consulted.
(4) If the circuit breaker is overheating be-
(4) Overloading (continuous or prolonged
current in excess of circuit breaker rating).
cause of excess current, one of two remedies
can be followed:
(a) Replace with circuit breaker having an
adequate rating for the present or future load.
(b) Arrange circuits to remove the excess
load.
(5) If the bars or cables overheat because of
(5) Transmission of heat to the circuit break-
current in excess of their capacity, this can be
ers from overheated or inadequate cables or
remedied by increasing the carrying capacity
connection bars.
(that is, increasing the size or number of con-
ductors) or by removing the excess current
from the circuit.
(6) Tighten.
(6) Loose connections or terminal connectors.
(7) Relocate in a cooler place, or arrange some
(7) Ambient temperature is too high.
means of cooling.
(1) Lubricate mechanism. Adjust all mechani-
(1) Mechanism binding or sticking. Caused
Failure to trip
cal devices, such as toggles, stops, buffers, and
by lack of lubrication or mechanism out of
opening springs, according to the instruction
adjustment.
book.
(2) Examine the latch surface. If worn or cor-
(2) Failure of latching device.
roded, it should be replaced. Check latch wipe,
and adjust according to the instruction book.
(3) Replace damaged coil.
(3) Damaged trip coil.
(4) Replace blown fuse.
(4) Blown fuse in control circuit (where trip
coils are potential type).
(5) Faulty connections (loose or broken wire)
(5) Repair faulty wiring. See that all binding
in trip circuit.
screws are tight.
(6) Dress or replace damaged contacts or
(6) Damaged or dirty contacts on tripping
device.
clean dirty contacts.
(1) Mechanism binding or sticking because of
(1) Lubricate mechanism. Adjust all mechani-
Failure to close or to latch closed
lack of lubrication or improper adjustment of
cal devices, such as toggles, stops, buffers, and
the circuit breaker mechanism.
opening springs, to specifications in the circuit
breaker instruction book.
(2) Burnout of operating (closing) coil (of
(2) Replace damaged coil and teach the users
the proper method of operation. A better rem-
electrically operated breakers) caused by op-
erator holding the control switch closed too
edy would be to change the connections to in-
clude an auxiliary switch, which automatically
long.
cuts off the closing coil as soon as the circuit
breaker closes.
(3) Closing relay sticking.
(3) Check or adjust the closing relay.
8-13
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