the breaker rated continuous current
to each pole. The significant part of
this test is the automatic opening of
the circuit breaker and not tripping
times as these can be greatly affected
by ambient conditions and test condi-
2.2.5. Mechanical operation.- The
mechanical operation of the breaker
should be checked by turning the
breaker on and off several times.
SECTION 3 - MAINTENANCE OF
LOW-VOLTAGE CIRCUIT BREAKERS
3.1. FREQUENCY OF MAINTENANCE.-
Low-voltage circuit breakers operating at
600 volts alternating current and below
should be inspected and maintained very
1 to 3 years, depending on their service
and operating conditions. Conditions that
make frequency maintenance and
inspection necessary are:
a. High humidity and high ambient
b. Dusty or dirty atmosphere.
c. Corrosive atmosphere.
d. Frequent switching operations.
e. Frequent fault operations.
f. Older equipment.
A breaker should be inspected and
maintained if necessary whenever it has
interrupted current at or near its rated
3.2. MAINTENANCE PROCEDURES. -
Manufacturer's instructions for each cir-
cuit breaker should be carefully read and
followed. The following are general pro-
cedures that should be followed in the
maintenance of low-voltage air circuit
a. An initial check of the breaker
should be made in the TEST position
prior to withdrawing it from to enclo-
b. Insulating parts, including bush-
ings, should be wiped clean of dust
c. The alignment and condition of the
movable and stationary contacts
should be checked and adjusted ac-
cording to the manufacturer's
d. Check arc chutes and replaces
any damaged parts.
e. Inspect breaker operating mecha-
nism for loose hardware and missing
or broken cotter pins, etc. Examine
cam, latch, and roller surfaces for
damage or wear.
f. Clean and relubricate operating
mechanism with a light machine oil
(SAE-20 or 30) for pins and bearings
and with a nonhardening grease for
the wearing surfaces of cams, rollers,
g. Set breaker operating mechanism
adjustments as described in the
manufacturer's instruction book. If
these adjustments cannot be made
within the specified tolerances, it may
indicate excessive wear and the need
for a complete overhaul.
h. Replace contacts if badly worn or
burned and check control device for
freedom of operation.
(FIST 3-16 1/92)