Page
5
4.
MANUAL OPERATIONAND TRIP UNIT
ADJUSTMENT
ManualOperation
Manualoperation of the circuit breaker is controlled by
the MCP handle and the PUSH
-
TO
-
TRIP button in the
trip unit. The MCP handle has three positions,two of
which are shown on the cover with raised letteringto indi
-
cate
ON
and OFF. On the handle,
ON,
OFF, and TRIP
are also shown by a color
-
coded strip for each MCP han
-
dle position: red for
ON,
white for TRIP, and greenfor
OFF (see Fig. 4
-
1).
MCP Reset
After a trip operation, the MCP is reset by movingthe
MCP handleto the Reset (extreme OFF) position.
Note: Inthe event of an automatictripping operation,
no MCP should be reclosed until the cause of trip is
known and the situation rectified.
PUSH
-
TO
-
TRIPButton
The PUSH
-
TO
-
TRIP buttonoperatesthe MCP tripping
function and may be usedto periodicallyexercisethe
operating mechanism.The rating plug in electronictrip
unitscontains the PUSH
-
TO
-
TRIPbuttonwhich is oper
-
ated by finger pressure.
ElectronicTrip Unit Adjustment
The instantaneoustrip level of the trip unit can be
adjusted by rotatingthe adjustment switchon the front
face of the trip unit with a screwdriver. The switch has
several settings as indicatedon the nameplatewith let
-
ters A through H (Fig.4
-
1). The ampere settings are
shownonthe MCP nameplateand in Table4
-
1. To adjust
the setting, rotatethe switch clockwise until arrow on
switch pointsto desired setting.
Trip Units
For additional informationon electronictrip units, referto
5.
INSPECTIONAND FIELDTESTING
MCPs are designedto provideyears of almost
maintenance
-
freeoperation.The following procedure
describes how to do a limited amount of field inspection
and testing of an MCP.
Inspection
MCPs in service should be inspectedperiodically.The
inspectionshould includethe followingchecks 5
-
1
through
5
-
8.
a
WARNING
THE VOLTAGES IN ENERGIZEDEQUIPMENTCAN
CAUSE SEVERE PERSONAL INJURY
OR
DEATH.
BEFORE INSPECTINGTHE MCP IN AN ELECTRICAL
SYSTEM, MAKE SURE THE MCP
IS
SWITCHEDTO
THE
OFF
POSITIONAND THAT THERE
IS
NO
VOLTAGE PRESENTWHERE WORK
IS
TO BE
PERFORMED.
A
A
CAUTION
SOME COMMERCIAL CLEANING AGENTS WILL
DAMAGETHE NAMEPLATES
OR
MOLDED PARTS.
MAKE SURE THAT CLEANINGAGENTS
OR
SOLVENTS USEDTO CLEANTHE MCP ARE
SUITABLE FOR THE JOB.
5-1.
5-2.
5-3.
5-4.
5-5.
Remove dust, dirt, soot, grease, or moisturefrom
the surfaceof the MCP using a lint
-
free dry cloth,
brush, or vacuum cleaner.
Do
not blow debris into
MCP. If contamination is found, look for the source
and eliminatethe problem.
Switch MCPto
ON
and OFF several times to be
sure that the mechanical linkagesoperatefreely
and do not bind. If mechanicallinkagesdo not oper
-
ate freely, replace MCP.
With the MCP in the
ON
position, pressthe PUSH-
TO
-
TRIP buttonto mechanicallytrip the MCP. Trip,
reset,and switch MCP
ON
several times. If mecha
-
nism does not reset each time the MCP is tripped,
replacethe MCP.
Check base,cover, operating handle,and handle
barrierfor cracks, chipping, and discoloration. MCP
should be replaced
if
cracksor severe discoloration
is found.
Checkwireconnectingterminals andothertype bus
bar connectors for loosenessor signs of overheat
-
ing.Overheatingwill show as discoloration,melting,
or blisteringof conductor insulation,or as pitting or
meltingof conductorsurfacesdue to arcing. If there
is no evidenceof overheatingor looseness,do not
disturb or tighten the connections. If there is evi-
40752-081(1) Effective2/03
Instruction Leaflet 40752-072
