SECTION 9-Fused Breakers (Cont.)
9.3 OPEN FUSE LOCKOUT DEVICE
This device automatically trips the fuse breaker if one of
the fuses opens. When this happens, the breaker is locked
open until the reset button of the phase involved is pushed.
The breaker should not be reclosed, of course, until the
opened fuse is replaced.
Type D breakers use the Open Fuse Lockout (OFLO)
shown in Fig. 55. Type A and B breakers use the OFLO
shown in Fig. 56A & 568. Both OFLO's work on the same
design. When the fuse opens, the resulting open c ircuit
voltage activates the OFLO phase solenoid when the
voltage level reaches approximately 90 VAC (the functional
test in the factory is accom p lished using 1 20VAC). The
solenoid armature then d rives a tri pping rod against a trip
paddle which is attached to the trip shaft. This causes the
breaker to open. The armature also d rives the reset button
forward indicating what phase is involved. The reset
button linkage also holds the tripping rod against the trip
paddle. The button must be pushed i n to release the
tripping rod.
9.3 . 1 TYPE A AND B BREAKER OFLO
ADJUSTMENT
To adjust the Type A and B breaker O FLO (Refer to Fig
56A):
a) Back off tripping rod so that it will not hit the trip
paddle when a solenoid is activated.
b) Using the maintenance handle, close the breaker.
c) Manually close the Left pole armature. Screw tripping
rod forward until it moves the trip paddle enough to open
the breaker. Add two full additional turns.
d) Close the breaker.
e) Manually close the Left pole armature again. The
breaker must open and the reset button pop out. In this
condition close the breaker, it should trip-free.
f) Reset the OFLO, the breaker must now be able to
close.
g) Repeat for Center and Left poles.
h) Check for a . 1 25" minimum clearance between trip
ping rod and trip paddle with the OFLO reset. Check for
.032" minimum overtravel after tripping rod trips breaker.
i) Hold tripping rod in position and tighten its locknut.
FIG. 55- TYPE D B R EAKER OFLO DEVICE
9.3.2 TYPE D BREAKER OFLO
ADJUSTMENT
To adjust the Type D breaker O FLO :
a) With the breaker in the C LOSED position and the
OFLO reset
,
adjust the dimension between the end of the
tri p ping rod and the trip paddle to .1 00" - . 1 40 " .
b ) With the O FLO energized, the breaker must TRIP
and the R ESET button must move forward to the front
plate. In this condition, the breaker must be held trip-free.
43
www
. ElectricalPartManuals
. com