Multi-Amp CB-832 User manual

Part 12470
Rev. 2 3/25/99
INSTRUCTION MANUAL
For
HIGH CURRENT TEST SET
MODEL CB-832
It is essential that this instruction book be read thoroughly before putting the equipment in service.
Advanced Test Equipment Rentals
www.atecorp.com 800-404-ATEC (2832)
®
E
s
t
a
b
l
i
s
h
e
d
1
9
8
1

Part 12470
Rev. 2 3/25/99
IMPORTANT
The information and data contained within this instruction manual are proprietary with MULTI-
AMP Corporation. The equipment described herein may be protected by one or more U.S. letters
patent. MULTI-AMP specifically reserves to itself all rights to such proprietary information aswell
as all rights under any such patent, none of which is waived by the submission of this instruction
manual to anyone.
The recipient, if a Government agency, acknowledges that this instruction book and the equipment
described were procured with "Limited Rights" to technical data as described in ASPR 9-203 (b).
Copyright MULTI-AMP Corporation, 1983,1984 ,1985,1986,1987,1988,1989,1991

Part 12470
Rev. 2 3/25/99
i
TABLE OF CONTENTS
SECTION PAGE
I. INTRODUCTION ............................................................................................................. 1
A. Specifications.............................................................................................. Bulletin
B. General Information............................................................................................... 1
C. About This Manual................................................................................................ 1
D. Safety Precautions.................................................................................................. 2
II. THEORY OF OPERATION.............................................................................................. 3
A. Description of Controls.......................................................................................... 3
B. Selection of Output Terminal ................................................................................ 6
C. Selection of Output Leads...................................................................................... 6
D. Overload Capacity .................................................................................................. 7
III. TEST PROCEDURES....................................................................................................... 8
A. Maintenance of Motor Overload Relays................................................................ 8
1. Planned Maintenance Program................................................................. 10
2. Time Delay................................................................................................ 11
3. Instantaneous Element.............................................................................. 13
B. Maintenance of Molded Case Circuit Breakers........................................ 15
1. Planned Maintenance Program................................................................. 15
2. Thermal Element....................................................................................... 16
3. Instantaneous Element.............................................................................. 18
4. Ground Fault Element............................................................................... 19
IV. SERVICE DATA 21
A. Service and Repair Order Instructions.................................................................. 22
B. Preparation for Reshipment .................................................................................. 23
C. Operational Errors/Troubleshooting..................................................................... 23
D. Warranty ............................................................................................................... 25
V. SCHEMATICS................................................................................................................. 26

Part 12470
Rev. 2 3/25/99
1
SECTION I
INTRODUCTION
GENERAL INFORMATION
TheMulti-AmpModelCB-832is aself-containedtest setwhichincorporatesavariablehighcurrent
output and appropriate control circuitry and instrumentation for testingthermal ,magnetic, or solid-
state motor overload relays, molded-case circuit breakers and ground fault trip devices.
ABOUT THIS MANUAL
This manual provides the user with all of the necessary information for complete working
understanding of the CB-832 test set. It is divided into five main sections.
SECTION I Gives a description of the test set. Gives basic guidelines on the
different applications performed with it.
SECTION II Is a detailed guide to all the controls and operating modes of the CB-
832. This section is by far the most important for understandinghow
to use the test set.
SECTION III Contains selected test procedures for motor overload relays and
molded case circuit breakers.
SECTION IV This section contains a troubleshooting guide and service and repair
information.
SECTION V This section contains a schematic drawing of the test set.

Part 12470
Rev. 2 3/25/99
2
SAFETY PRECAUTIONS
Every consideration has been given to the designand constructionof the Multi-Amp ModelCB-832
Portable High Current Test Set to make it a safe piece of test equipment as well as one that is
accurate, reliable, and easy to use.
WARNING
The Model CB-832 is not designed for use on energized circuits. For the safety of the operator and
protection of the instrument, do not connect it to circuits that are energized. This includes circuits
that could become energized during the course of a test procedure utilizing this instrument.
It must be remembered that the test set is capable of producing voltageand currentlevelsthat can be
deadly if personnel come in contact with them.
For safe operation, it is absolutely essential that the technician properly and effectively ground
(earth) the test set. This is accomplished by connecting the input line cord to a properly grounded
receptacle.
CAUTION
The input voltage of this instrument is not selectable. All the units are shipped from the factory set
up for operation from either a nominal 115 volt or 230 volt source. If the unit is to be used on a
voltage source different than the nameplate specifies, major changesin thetest set arerequired. It is
necessary for the technician to contact the factory to obtain the necessary parts and instructions
before attempting to change the input voltage of the test set.
The CB-832 should be properly operated by qualified personnel who have familiarized themselves
with the test set and thoroughly read the instruction manual provided with it.
If questions arise concerning the care, operation, maintenance or application of the test set, contact
the Multi-Amp Corporation for assistance.

Part 12470
Rev. 2 3/25/99
3
SECTION II
THEORY OF OPERATION
DESCRIPTION OF CONTROLS
This section of the instruction manual describes thefunctionsof allthe variouscontrol switches, etc.
which are located on the control panel of the Model CB-832. All controls are clearly marked and
logically grouped so that continual reference to the instruction manualshouldnot benecessaryafter
the operator has become acquainted with the operation of the test set.
POWER ON/OFF Switch
Controls input power to the test set. The self-protected switch resets
after an overload, when placed in the OFF position. Displays will
light when the switch is ON.
MAIN FUSE
Protects power output circuit of CB-832 against overloads.
CONTROL FUSE
Protects instrumentation and control circuitry against overloads.
OUTPUT CONTROL
Variable autotransformer provides continuous non-stepped output
froma varietyof current-ratedterminals. Outputsystemiscontrolled
by a combination of timer STOP MODE and OUTPUT MODE
Switch positions.
OUTPUT ON Lamp
Lights whenever output control circuit is energized.
OUTPUT Terminals:
A combination of the COMMON terminal and any one of the three
current-designated terminals provides an output circuit. Refer to
other sections of the text for an explanation of the output
characteristics of these terminals.
NOTE: Thecurrentdesignationoftheseterminalshasno bearingontheactualcurrentoutput
capability of each. Much higher currents can be achieved depending on test circuit
impedance and duration of the test.

Part 12470
Rev. 2 3/25/99
4
OUTPUT MODE Switch
Initiates the output circuit in conjunction with the appropriate Timer
STOP MODE Switch position.
MOMENTARY
Momentary on position with spring return to OFF. Output will
remain energized as long as switch is held in MOMENTARY
position and is de-energized when released. Timerstartsand stops in
the same manner. Used for jogging the output circuit.
MAINTAIN
Maintained on position with spring return to OFF. Output will
remain energized until appropriate STOP MODE function occurs,
switch is moved to OFF position or current drops below threshold
requirement.
OFF
Test set input power remains energized but output current remains
de-energized and timer will not count.
AMMETER
LED displays show the numeral one in the left most position when
the meter is over-ranged.
RANGE SWITCH
Decimal of display shifts one digit to the right for each increase in
range selection.
DISPLAY MODE Switch
Selects either the NORMAL or MEMORY mode of the ammeter.
NORMAL
Ammeter updates reading continually as long as the output is
energized. Reading is lost when the output is de-energized.
MEMORY
Ammeter retains the highest peak value attained during current
output operation above 8% of the full scale of range selected.
Reading is retained until the output is reinitiated or RANGE
SWITCH position is changed.
TIMER
Automatically resets each time output is reinitiated.
CYCLES/SEC. Switch
Selects cycles or seconds mode.

Part 12470
Rev. 2 3/25/99
5
CYCLES Position
The timer counts in whole
cycles and uses the power
input line frequency as timing
reference.SEC. Position
The timer counts in two selectable increments and uses an internal
10kHz oscillator as timing reference.
.01/.001 Switch
Selects one of two counting increments available for the timer SEC.
mode.
NOTE: Changing the position of the CYCLE/SEC. Switch (or the .01/.001 Switch while in
the SEC. position) during timer operation will produce erroneous readings.
CONTACTS Binding Posts
Circuit controls output and timer in the normally open or normally
closed positions of the STOP MODE Switch.
NOTE: Do not connect CONTACTS binding posts to an energized circuit.
STOP MODE Switch
Selects either current actuated position to stop the current output and
timer, or either of the two external contact stop mode positions.
NORM. OPEN
With CONTACTS binding posts connected to normally open
contacts, output circuit will remain energizedand timerwill continue
to run until contacts close.
NORM. CLOSED
With CONTACTS binding posts connected to normally closed
external contacts, output circuit will remain energized and timer will
continue to run until contacts open.
CURRENT
Timer will initiate only when the output circuit is completed and a
threshold current of approximately 8% offull scale of ammeter range
selected is exceeded. Timer will continue to run until output circuit
opens, current drops below threshold level or output is de-energized.

Part 12470
Rev. 2 3/25/99
6
SELECTION OF OUTPUT TERMINAL
Three output terminals at various voltage and current ratings are provided to adapt the CB-832 to a
wide variety of test circuit impedances.
TheMulti-AmpModelCB-832circuitbreakertestset hasthreecurrentoutputterminalstoprovidea
wide range of current-voltage capabilities. The terminal with the lower current rating provides an
output with the highest voltage for testing devices of low current requirements but with high
impedance characteristics. This tap also has the highest output resolution capable of fine current
adjustments. The highest current rated output terminal provides high current availabilityfor testing
devices of high current requirements of relatively low impedance. This tap offers the highest
resolution for voltage applications. Should the current required for the device to be tested exceed
the ability of the lowest tap or the impedance of the device to be tested require more voltage to
"push" the current than is available from the highest current tap, the medium range current tap can
be utilized to provide the current or voltage necessary to perform the desired test. Selection of the
output terminal depends entirely on the characteristics of the device to be tested, therefore, proper
selection will require some experimentation and will be easier as familiarity increases.
NOTE: There is no relationship between the ammeter ranges and the ratings of the output
terminal. All ammeter ranges can be used in conjunction with any of the output
terminals.
SELECTION OF OUTPUT LEADS
Model CB-832 is equipped with output connecting bars for attachment of the high current testleads
provided or any others suitable for the test application.
The following information on the selection of output leads will provide the user with a guide for
choosing the proper test leads for his application.
Due to the voltage drop from the inductive reactance of the test circuit, a significant loss of
current will result for each inch of test lead. Therefore, when choosing test leads, the length
and size of leads chosen will determinethe maximumavailable test current. It isworthwhile
to sacrifice cross section of test leads for the sake of reducing length. Everyinch of lead that
can be eliminated provides worthwhile increase in available test current. Heating is not a
significant problem in testing, even though the leads become hot. Paralleling of sufficient
cables provides highertest currents. Each cable can befittedwitha compressionlug oneach
end, then bolted to the output terminals or stab board of the test set and the breaker.
The two cables between the test set and the breaker should be twisted together or bundled
with tape or cord to maintain the close proximity, which minimizes inductive reactance.
OVERLOAD CAPACITY

Part 12470
Rev. 2 3/25/99
7
Model CB-832 is rated at 1.75 kVA output and is equippedwith three output terminals, each capable
of supplying its rated current. The current rating of these output terminals may be exceeded for
short durations provided the voltage rating is sufficient to "push" the desired current through the
device under test and the connecting test leads. The overload capacity, represented by multiples of
rated current, versus TIME ON and TIME OFF are given below.
%Rated Maximum Minimum
Current Time ON Time OFF
100 (1x) 30 minutes 30 minutes
200 (2x) 3 minutes 8 minutes
300 (3x) 30 seconds 4 minutes
400 (4x) 7 seconds 2 minutes
Model CB-832 also can be used continuously for any reasonable length of time at 70.7% of the
current rating of the output terminal.
EXAMPLE:
Consider the terminal rated at 500 amperes:
a. 500 amperes may be drawn at any voltage from 0-3.5 volts for 15 minutes provided
the test set is subsequently de-energized for 30 minutes.
b. 353.5 amperes (70.7% of 500 amperes) may be continuously drawn at any voltage
from 0-3.5 volts for any reasonable length of time.
c. Thefollowingoverloadcurrentsmaybe drawnat anyvoltagefromzeroto maximum
volts for the Time ON indicated, followed by the indicated Time OFF. The
maximum output voltage available when the current rating of the output terminal is
exceeded (overloaded) will be less than the rated value due to the regulation of the
transformer in the test set. For example, when drawing 750 amperes from the 500
ampere terminal, the maximum voltage available is approximately 2.9 volts.
500 Ampere Time ON Time OFF
750 amperes 6 minutes 13 minutes
1000 amperes 3 minutes 8 minutes
It should be noted that because of the impedance of the device under test and the connecting test
leads, the maximum practical test current available from the terminal rated 500 amperes is

Part 12470
Rev. 2 3/25/99
8
approximately 1000 amperes. Higher currents are usually available from the terminal rated 500
amperes; HOWEVER, these higher currents are availableonlyfor very short durations asillustrated
in the overload capacity table above. For example, it is possible to get 1800 amperes from this
terminal through a typical 225 ampere molded case circuit breaker for an instantaneous trip test.
SECTION III
TEST PROCEDURES
MAINTENANCE OF MOTOR OVERLOAD RELAYS
The prime function of the motor overload relay is to prevent operation of a motor for too long a
period of time when an overload condition exists.
In general, motor starters are applicable to a given horsepower range of motors. The voltage and
current requirements of the application will "size" the starter under NEMA requirements, but the
actual starting current, running current and ambient temperature will determine the overload relay
rating required to protect the motor without nuisance tripping.
Selection of the properly rated overload relay can be made by reference to tables or charts supplied
by the manufacturer of the overload relays and motors. Whenever a motor trips out, it is poor
practice to uprate the overload relay indiscriminately; the motor may actually be working under an
overload condition or the overload relay may be operating improperly. Uprating the overload relay
could permit an overloadto continue, resultingin deteriorationof the motorinsulation and reduction
in motor life. Therefore, careful analysis should be made as to the cause of the nuisance trip before
changing the rating of the overload relay.
Operating characteristics ofthe motor overloadrelayshouldbe verifiedat regularintervals. Typical
practice dictates inspection of overload relays at periods of one to two years, with an actual test of
tripping time to be made at intervals of two years. The test interval can vary with thetype of service
involved and the importance of the motor to process or production.
Motor overload relays incorporate an element which actuates a set of contacts connected to the
motor control circuit. These contacts open the circuit of the holding coil in the motor starter and
interrupt the power to the motor.
In general, there are three types of motor overload relays in use:

Part 12470
Rev. 2 3/25/99
9
1. Thermal - melting alloy or solder pot
2. Thermal - bimetallic strip
3. Electromagnetic
In thermal type relays, time-current characteristics are obtained by the thermal properties of the
melting alloy or bimetallic strip. In the magnetic type, a damped plunger or moving iron device is
used to produce time delays.
1. Thermal - melting alloy or solder pot
In this type, tripping is the result of heat generated bythe motor loadcurrent passingthrough
a "heater" in the overload relay. This overload relay consists of a brass shaft which is
surrounded by solder. Fixed to one end of the shaft is a small ratchet wheel.
As long as the solder is solid, this assembly is immobile. When the motor control circuit
contacts are closed, a spring is held compressed by the immobility of the ratchet wheel. An
overloaded condition in the motor increases the current through the heater, thus melting the
solder and releasing the energy in the spring. This interrupts the circuitof the holdingcoil in
the motor starter and shuts down the motor.
The starter may be reset only after the temperature of the heater has cooled sufficiently to
permit the solder to solidify and again make the ratchet and shaft immobile. Reset isusually
accomplished by an external pushbutton on the face of the starter. Many heaters offer a
selection of either manual or automatic reset.
2. Thermal - bimetallic strip
This type uses a bimetallic strip - two pieces of dissimilar metal bonded together. An
increase in heat will cause movement of this bimetallic unit and eventually open a set of
contacts in the motor control circuit, thus opening the holding coil circuitand shuttingdown
the motor.
The principle of operation is the same as the melting alloy type. When the bimetallic
element has cooled sufficiently, the motor control circuit may be reset either manually or
automatically.
3. Electromagnetic
In this type of motor overload relay, a damped plunger or moving iron device is used to
produce the delays required and initiate the trip signal to the interrupting device. The most

Part 12470
Rev. 2 3/25/99
10
common typeof magnetic overload relay utilizesa plungeror ironcore pistonwhichextends
from an oil filled dashpot into the operating coil of the relay.
When the electromagnetic field produced by the operating coil is strong enough, the piston
moves through the oil and opens the contacts of the relay. A time-delay is achieved by the
oil in the dashpot, retarding the movement of the piston. Usually magnetic overload relays
with oil dashpots have facilities which permit adjusting their minimum operating current
(pick-up point) and their time delay characteristics.
PLANNED MAINTENANCE PROGRAM
A scheduled program for maintenance of motor overload relays consists primarily of "good
housekeeping" in conjunction with visual inspections and electrical tests. A brief outline is given
below:
1. Clean
All types of motor overload relays should be cleaned periodically to ensure continued,
reliable operation. It is possible for dirt or dust,created byconditionsin theplant,to prevent
parts of the relay from moving. These same conditions can also prevent the proper
dissipation of normal heating, resulting in unnecessary operation of thermal type overload
relays.
2. Tighten Connections
This is particularly important in thermal overload relays. Loose electrical connections can
cause extra heat which may result in a nuisance operation of the relay.
3. Inspect Heater Size
Determine that the specified heater is used in thermal overload relays. Too often, oversized
heaters are arbitrarily installed to eliminate unexplained trips. Actually, the original heaters
may have oxidized after a period of time and become smaller in cross section. In that event,
the heat required to operate the relay is provided by a smaller amount of current than that
intended by the original design. This may make the relay trip prematurely and the heater
appear undersized.
4. Inspect Settings (Where applicable)
Most magnetic overload relays have adjustable settings for minimum operating current and
time delay characteristics. These should be adjusted to the specified settings.

Part 12470
Rev. 2 3/25/99
11
5. Test
The motor overload relay should be subjected to a simulated overload and the tripping time
measured. This should be compared to the manufacturer's specifications or the relay's time
curves to make certain that the relay is operating properly. A tolerance of + 15% is usually
acceptable. If the relay's curves or specifications are not available, it is suggested that the
Heat Damage Curve of the motor be used as a guide for maximum trip time at 300% of
motor full load current. TIME DELAY OF MOTOR OVERLOAD RELAYS
TIME DELAY
1. Set-up CB-832 with:
a. POWER ON/OFF Switch in OFF position (instrument displays off).
b. OUTPUT CONTROL knob at minimum `0' position.
c. OUTPUT MODE Switch in center OFF position.
2. Connect one end of a high-current lead to one side of thermal element or current coil
in overload relay. Connect other end of this lead to the COMMON terminal of test
set.
3. Connect one end of second high-current lead to other side of thermal element or
current coil in overload relay. Connect other end of this lead to the appropriate
output terminal (see SELECTION OF OUTPUT TERMINAL).
4. Connect test set to suitable single-phase power supply.
5. Turn test set on with POWER ON/OFF Switch (instrument displays should light).
6. Use RANGE Switch to select ammeter range so test current will be near full scale
and no less than 10% of full scale.
7. Put ammeter DISPLAY MODE Switch in MEMORY position.
8. Connect a pair of light leads (timer leads) from Normally Closed Contacts or
Normally Open Contacts of overload relay to binding posts of test set labeled
CONTACTS.
9. Select appropriate timer STOP MODE.
10. Select desired timer display mode and range.
11. Rotate OUTPUT CONTROL knob clockwise and momentarily press OUTPUT
MODE Switch in MOMENTARY and release. Observe current reading retainedby
ammeter.
12. Continue to rotate OUTPUT CONTROL knob clockwise while jogging (repeatedly
moving to MOMENTARY position and releasing) OUTPUT MODE Switch until
desired test current is reached. Suggestedtest currentis three times(3x) the ratingof
thermal relays or three times (3x) the pick-up current of magnetic relays.
If the relay utilizes a high impedance thermal element or operating coil and the

Part 12470
Rev. 2 3/25/99
12
desired test current cannot be reached, transfer output lead to the next higher voltage
(lower current) terminal, and repeat Steps 11 and 12. If test current is still not
reached,transferoutputleadto terminallabeled25A,andrepeatSteps11 and12(see
SELECTION OF OUTPUT TERMINAL).
NOTE: Before starting test, allow time for thermal element to cool; or in the case of
magnetic overload relays, for the piston to reset. Incorrect tripping time may
otherwise result.
13. Put ammeter DISPLAY MODE in NORMAL position.
14. Start test by moving OUTPUT MODE Switch to MAINTAIN position.
NOTE: Test current may decrease (fall off) during the test because the resistance or
impedance of the test circuit increases as it heats up. Rotate OUTPUT CONTROL
knob clockwise to keep test current at desired value.
15. When overload relay trips, timer stops and output is de-energized. Timer indicates
total elapsed time of the test in seconds or cycles.
16. Turn test set OFF with POWER ON/OFF Switch.
17. Record test results.
IMPORTANT
In order to obtain accurate tripping times with some types of magnetic overload relays, particularly
those using high viscosity oil, it may be necessary to "preheat" the relay by running rated current
through the relay for a few minutes.
INSTANTANEOUS ELEMENT
1. Set-up CB-832 with:
a. POWER ON/OFF Switch in OFF position.
b. OUTPUT CONTROL knob at minimum, `0' position.
C. OUTPUT MODE Switch in center OFF position.

Part 12470
Rev. 2 3/25/99
13
2. Connect one end of a high-current lead to one side of instantaneous element in
overload relay. Connect other end of this lead to the COMMON terminal of test set.
3. Connect one end of second high-current lead to other side of instantaneous element
in overload relay. Connect other end to the appropriate output terminal (see
SELECTION OF OUTPUT TERMINAL 4).
4. Connect test set to suitable single-phase power supply.
5. Turn test set on with POWER ON/OFF Switch (instrument displays should light).
6. Use RANGE Switch to select ammeter range so test current will be near full scale
and no less than 10% of full scale.
7. Put ammeter DISPLAY MODE in MEMORY position.
8. Connect a pair of light leads (timer leads) from Normally Closed Contacts or
Normally Open Contacts of overload relay to binding posts of test set labeled
CONTACTS.
9. Select appropriate timer STOP MODE.
10. Select desired timer display mode and range.
11. Rotate OUTPUT CONTROL knob clockwise and momentarily press OUTPUT
MODE Switch in MOMENTARY and release. Observe current reading retainedby
ammeter.
NOTE: If the relay utilizes a high impedance instantaneous element and the desired test
current cannot be reached, transfer output lead to the next higher voltage, lower
current terminal, and repeat Step 11.
12. Continue Step 11 until overload relay trips. Observe current reading retained on
ammeter. Timer indicates elapsed time of test in cycles or seconds.
NOTE: To avoid tripping error caused by interference of time delay element, allow thermal
element to cool; or in the case of magnetic overload relays, for the piston to reset.
13. Repeat test, starting with OUTPUT CONTROL knob at position just below trip
current of instantaneous element observed in Step 12.

Part 12470
Rev. 2 3/25/99
14
14. When overloadrelay trips,timerstopsand outputis de-energized. Currentreadingis
retained on ammeter. Timer indicates elapsed time in seconds or cycles.
15. Turn test set OFF with POWER ON/OFF Switch.
16. Record results.
IMPORTANT
Refer to manufacturer's instructions for instantaneous trip time. If increasing test current does not
decrease tripping time, current at which minimum tripping time was first observed is the
instantaneous trip current value. Additionally, the test method outlinedaboveis sometimesreferred
to as the "jogging" or "step" method. For nearly all applications, this method works best; however,
there is another method referred to as the "run-up" method. Instead of the OUTPUT MODESwitch
being in the MOMENTARY position, it is placed in the MAINTAIN position and the ammeter is
placed in the NORMAL position. When the output is initiated, rotate OUTPUT CONTROL knob
clockwise and observe current reading on ammeter. When the device trips, record trip current. If
this method is used, it should be noted that the device is being heated with continuous current,andit
is hard on the variable auto transformer windings and brush(es) (can cause premature wear-down of
the brush(es) and carbon buildup - see SERVICE DATA).

Part 12470
Rev. 2 3/25/99
15
MAINTENANCE OF MOLDED CASE CIRCUIT BREAKERS
The molded case circuit breaker essentially consists of two separate elements. One element is a set
of contacts and suitable mechanical linkage for manual operation of the breaker as a switch in an
electrical circuit. The other element is a device that senses and reacts to anoverload orshortcircuit.
Normally, the time delay overload device is thermal and the instantaneous overload device, when
supplied, is magnetic. The thermal element usually uses a bimetallic strip; two pieces of dissimilar
material bonded together. An overload causes an increase in heat which will result in moving the
bimetallic unit and eventually trip the circuit breaker. The magnetic element operates with no
intentional time delay to provide instantaneous protection against high magnitude faults.
PLANNED MAINTENANCE PROGRAM
A scheduled program for maintenance of molded case circuit breakers consists primarily of "good
housekeeping" in conjunction with visual inspections and electrical tests. A brief outline is given
below:
1. Clean
All types of molded case circuit breakers should be externally cleaned so that the heat
produced in normal operation can be dissipated properly. It is possible for dirt or dust
caused by normal plant conditions to accumulate and prevent proper dissipation of heat,
resulting in a nuisance operation of the breaker.
2. Tighten Connections
This is particularly important because loose electrical connections can cause extra heat
which may result in an unnecessary operation of the breaker.
3. Test
The molded case circuitbreakershouldbe subjected toa simulated overloadand the tripping
time measured. This is important because after a period of inactivity, the overload device
may become stiff or inoperable. The only wayto determine this condition and eliminate the
stiffness is to electrically operate the breaker on a periodic basis. Manually opening and
closing the main contacts of the breaker does not move any of the mechanical linkage
associated with the overload device. Testing may beas often as every 6months or aslongas
every three or four years, depending upon conditions where the breaker is installed.
THERMAL ELEMENT

Part 12470
Rev. 2 3/25/99
16
1. Set-up CB-832 with:
a. POWER ON/OFF Switch in OFF position (instrument displays OFF).
b. OUTPUT CONTROL knob at minimum, `0' position.
c. OUTPUT MODE Switch in center OFF position.
2. Connect one end of a high-current lead to one pole of circuit breaker. Connect the
other end of this lead to the COMMON terminal of test set.
3. Connect one end of the second high-current lead to the other side of the same pole of
the circuit breaker. Connect other end of this lead to the appropriate output terminal
(see SELECTION OF OUTPUT TERMINAL).
4. Connect test set to suitable single-phase power supply.
5. Turn test set on with POWER ON/OFF Switch (instrument displays should light).
6. Use RANGE Switch to select ammeter range so test current will be near full scale
and no less than 10% of full scale.
7. Put ammeter DISPLAY MODE Switch in MEMORY position.
8. Place timer STOP MODE Switch in CURRENT position.
9. Select desired timer display mode and range.
10. Rotate OUTPUT CONTROL knob clockwise and momentarily press OUTPUT
MODE Switch in MOMENTARY and release. Observe current reading retained by
ammeter.
11. Continue to rotate OUTPUT CONTROL knob clockwise while jogging (repeatedly
moving to MOMENTARY position and releasing) OUTPUT MODE Switch until
desired test current is reached. Suggestedtestcurrentis three times(3x) the ratingof
the circuit breaker.
If desired test current is not reached with OUTPUT CONTROL knob at maximum
clockwise rotation, return knob to zero and transfer output lead to the next higher

Part 12470
Rev. 2 3/25/99
17
voltage/lower current terminal. Proceed with currentadjustment as in Steps 10 and
11 (see SELECTION OF OUTPUT TERMINAL).
NOTE: Before starting test, allow time for the thermal element to cool, otherwise incorrect
tripping time may result.
12. Put ammeter DISPLAY MODE in NORMAL position.
13. Start test by moving OUTPUT MODE Switch to MAINTAIN position.
NOTE: Test current may decrease (fall off) during the test because the resistance or
impedance of the test circuit increases as it heats up. Rotate OUTPUT CONTROL
knob clockwise to keep test current at desired value.
14. When circuit breaker trips, timer stops and output is de-energized. Timer indicates
total elapsed time of the test in seconds or cycles.
15. Turn test set OFF with POWER ON/OFF Switch.
16. Record test results on Test Record Card.
IMPORTANT
Some types of circuit breakers are intended to trip only under high current fault condition, usually
ten times (10x) rated current. They have only instantaneous characteristics and therefore will not
trip using usual procedure described above.
INSTANTANEOUS ELEMENT
1. Set-up CB-832 with: