Asco 4900 Load Bank User manual

P/N: 1251794
4900 Load Bank
User Manual

ASCO MODEL 4900
OUTDOOR RESISTIVE LOAD BANK
Part Number 1251794
2500 kW, 480 VAC, 3 PH, 60 Hz
© 2018 ASCO Power Technologies, Inc. April 18, 2018
Cleveland, Ohio

6255 Halle Drive, Cleveland, OH 44125-4615 -216.573.7600 -f: 216.573.5953
www.avtronloadbank.com Form 831B-LB Rev. 11-16
PROPRIETARY NOTE
This document contains information PROPRIETARY TO Avtron
Load Bank branded products and systems by ASCO Power
Technologies, LP. It is furnished solely to provide information
sufficient for instruction, operation, maintenance, evaluation,
and testing of the equipment herein disclosed; is not to be used
for manufacturing or procurement; and is not to be disclosed to
anyone other than persons in the Division, or the Company, or
the Government, as the case may be, responsible for action
relating to this document without the express written permission
of ASCO Power Technologies, LP.
WARRANTY
The last page of this document contains an express limited
warranty. The provisions of this warranty cover any and all rights
extended to holders of Avtron Load Bank branded products and
systems by ASCO Power Technologies, LP.

ASCO POWER TECHNOLOGIES, INC.
Cleveland, Ohio
ASCO MODEL 4900
OUTDOOR RESISTIVE LOAD BANK
Part Number 1251794
TABLE OF CONTENTS
Page
Section I SAFETY CONSIDERATIONS...............................................................1-1
Section II DESCRIPTION........................................................................................2-1
Section III INSTALLATION ....................................................................................3-1
Section IV OPERATION........................................................................................... 4-1
Section V MAINTENANCE....................................................................................5-1
Section VI REPLACEMENT PARTS LIST.............................................................. 6-1
APPENDIX - Load Bank Troubleshooting Guide
DRAWINGS
SB3833 Outline Drawing, Load Bank
1252846 Schematic Diagram
D24712 Resistor Assembly
D26614 Resistor Assembly
SUPPLEMENTAL VENDOR MANUALS
Froment Intelligent Handheld Terminal (IHT) Quickstart Guide
-i-

1-1
ASCO MODEL 4900
OUTDOOR RESISTIVE LOAD BANK
Part Number 1251794
SECTION I
SAFETY CONSIDERATIONS
Throughout this manual, you will find WARNING and CAUTION statements. Personal injury or
death may occur to an operator using or repairing the equipment if a WARNING statement is
ignored. Damage to the equipment and potentially hazardous conditions for personnel may occur if
a CAUTION statement is ignored.
Each ASCO unit is safety checked for opens and shorts, and the insulation is high potential tested to
ensure safe operation. All fuses, safety interlocks, and related safety equipment have been proven
reliable as part of the testing procedure of each unit.
As part of your safety program, an initial inspection after receiving the unit(s) and periodic
preventive maintenance and safety inspections should be conducted to ensure the reliability and
safety built into your ASCO equipment.
The Load Bank is an industrial test unit designed to be used outdoors safely. However, because the
purpose of the Load Bank is to dissipate electrical energy, there are inherent dangers to operators
and equipment. These dangers are outlined in this section.
Electrical energy is transformed into heat by the resistors. This heat must be removed from the Load
Bank by the cooling blowers. If there is any restriction or stoppage of airflow, the Load Bank may
overheat and may even start a fire. It is recommended that:
1. The operator should read the manual before using the Load Bank.
2. Run an approved ground wire from the Load Bank ground lug to the generator frame. Run
an approved ground wire from the generator frame to a good earth ground.
3. Do not bypass the AIRFLOW safety switches or the OVERTEMPERATURE safety
switches to prevent nuisance tripping. The switches drop out if insufficient air is reaching
the load elements.

Safety Considerations ASCO 4900 Outdoor Resistive Load Bank • Part Number 1251794
1-2
4. Replace any burned out bulbs on the Control Panel. Each lamp is an indication that a system
is active or has failed and is important to the operation of the Load Bank and safety of the
operator.
5. Maintenance personnel must always exercise caution when the access panels are removed.
Personal injury from electrical shock or from the moving blower blades may result if all
sources of power are not disconnected before servicing. Maintenance work must be done
only by qualified personnel.
6. The Load Bank must be used in a cool, well ventilated area as described in the
INSTALLATION section of this manual. Do not allow exhaust air to recirculate through the
Load Bank.
7. Venting the heated air from the exhaust toward overhead cables, sprinkler systems, or into a
room with insufficient volume or "Make-Up" air is a potential hazard. The Load Banks
should be used in a cool, well ventilated area.
8. Allow cool room air to pass into the unit to cool the elements. Do not allow the unit to be
placed where hot exhaust air can recirculate back through the unit causing a constant rise in
cooling air temperature.
9. After running a load test, residual heat may be removed fromthe Load Bank by allowing the
blower to operate for a few minutes after the load is removed. This procedure is not required
for maintaining Load Bank integrity, but it may guard operating personnel from possible
burn injuries.
10. The operator should avoid coming in contact with the resistor elements or surrounding
covers during and for some time after operation. These portions of the Load Bank become
quite hot and may result in a serious burn should contact be made with them.
11. Do not allow objects to enter or block the air intakes or exhausts of the Load Bank. A
blockage would cause Load Bank overheating. If an object enters the screens, it will cause
damage to the resistor elements, possibly shorting them and causing shock and/or fire
hazards.
12. Consideration should be given to mounting surface material due to hot air exhaust.
13. Operators must not operatethe Load Bank with the access panels or screens removed. To do
so would expose the operator and other persons to possible personal injury from electrical
shock or from the moving fan blades.
14. Emergency Shutdown Procedure
A. In an emergency, press the STOP/RESET button located on the remote control panel,
this will disconnect both the load steps and fan/motor.

Safety Considerations ASCO 4900 Outdoor Resistive Load Bank • Part Number 1251794
1-3
15. An approved electrical fire extinguisher should be on hand at all times.
16. It is the responsibility of the customer to take diligent care in installing the Load Bank. The
National Electrical Code (NEC), sound local electrical and safety codes, and the
Occupational Safety and Health Act (OSHA) should be followed when installing the
equipment to reduce hazards to persons and property.
17. The load bank has special quick connect cam-lok style connectors for load connection. All
connectors must be fully engaged and share current before load is applied. Keep connector
covers on all locations when not in use, during transit, and during storage.
18. Louver cover plates must be removed from all four locations prior to operation. Replace
covers for storage and transport.
19. Read and heed all WARNING and CAUTION statements in the manual.

Description ASCO 4900 Outdoor Resistive Load Bank • Part Number 1251794
2-1
SECTION II
DESCRIPTION
ASCO Load Bank is an outdoor unit designed to absorb a balanced resistive load of unity power
factor, at a specified 3-phase voltage. The total load capability of the K975A Load Bank is 2500 kW
at 480 VAC, 3-phase, 60 Hz. The load steps are 50, 50, and (24) at 100 kW.
The Load Bank contains two 15 H.P. blower motors that operate from480 volts, 3-phase, 60 Hz, and
provide the necessary cooling air for the load elements. The blower motors derive voltage from the
main bus and are controlled by motor starter contactors. Overcurrent protection is provided by fuses
and overload relays. When an external source is used for blower and control power, its voltage may
be independent of the LOAD voltage of the generator under test. The blower air delivery is
27,000 CFM at 1.4 inch of static pressure.
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C A U T I O N
This Load Bank should never be used without the fan blower motors
operating. Inadequate cooling airflow will result in resistor elements
overheating and a definite fire hazard.
*************************************************************
Two airflow switches are provided to monitor the flow of cooling air. These differential pressure
switches are electrically interlocked with the load application controls to prevent load application if
the blowers are not working properly.
Two thermocouples are provided to sense the exhaust air temperature. The sensors are located at the
top of each exhaust heater case. The thermocouples are wired to an adjustable temperature sensor
set at a trip point of 350F. If the trip point is exceeded, it will prevent load application.

Description ASCO 4900 Outdoor Resistive Load Bank • Part Number 1251794
2-2
*************************************************************
C A U T I O N
Voltage must not be connected to the Load Bank resistance elements
if the airflow switches have not closed. It is the customer’s
responsibility to ensure all load is dropped if an air failure is detected.
DO NOT jumper out any air switches to prevent nuisance tripping.
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C A U T I O N
Voltage must not be connected to the Load Bank resistive elements if
any fault (overtemperature, motor overload, air failure) is indicated.
It is the customer’s responsibility to ensure all load is dropped if any
fault or alarm is detected.
*************************************************************
The K975A Load Bank is fabricated using heavy-gauge aluminized sheet steel to make a rigid
structure. Mounted within the structure are the load element resistor assemblies, the blower
assemblies, and the necessary load step contactors, motor starters, motor overload relays, fuses, and
customer connection bus bars. The cooling air is drawn in from one end, forced across the resistor
elements, and exhausted out the opposite end. The component enclosure compartment has a
temperature controlled heater that may be used toprevent condensation on the insideofthecontactor
enclosure of the Load Bank.
The units are equipped with louvers (with travel/storage covers) on the inlet and outlet openings that
protect the motors and resistor assemblies from the weather. The Load Bank uses a formed sheet
metal base to facilitate handling by a forklift truck. Bolt holes are supplied in the base to permit
permanent mounting to a pad.

Description ASCO 4900 Outdoor Resistive Load Bank • Part Number 1251794
2-3
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W A R N I N G
Never exceed the rated voltage as this will cause the Load Bank to
overheat.
Do not apply DC voltages as the contactors do not have arc blowout
magnets.
*************************************************************
Lower voltages may be applied to the load circuit of the Load Bank. The applied kW with a lower
voltage is computed with the following formula:
)
RatedVoltage(
)
AppliedVoltage(
kW
=
kW 2
2
RatedApplied 
CONTROL PANELS
The Load Bank utilizes two local, integrally mounted control panels. The first local control panel is
the interface between the Load Bank and the Intelligent Handheld Terminal (IHT), and is used the
unit is operating under Sigma control. The control panel contains a STATUS: UNIT ONT TEST
light, START pushbutton, a STATION SELECT switch, and a STOP/RESET pushbutton. The
control panel also includes the connection for the IHT.
The second control panel is a manual control panel that is used as a toggle-switch back-up for the
Sigma control system. A key-switch selects between the Sigma control panel and the Manual
control panel.
The manual control panel contains the OPERATION CONTROL Key-Switch, a CONTROL
POWER Switch, the BLOWER START and STOP pushbuttons, as well as a MASTER LOAD
switch, and toggle switches of 2 x 50 KW and 24 x 100 KW. Indicators include lamps indicated
TOP AND BOTTOM OVERTEMPERATURE, TOP AND BOTTOM AIR-FAIL, and BLOWER
POWER.

Installation ASCO 4900 Outdoor Resistive Load Bank • Part Number 1251794
3-1
SECTION III
INSTALLATION
BEFORE INSTALLATION
Inspect the Load Bank for obvious damage such as broken wires, broken or dented panels, cracked
ceramic insulators, or any other component breakage that may have occurred in shipment.
*************************************************************
W A R N I N G
It is vitally important to install the Load Bank properly. Installation
errors may result in a catastrophic failure. The airflow switches, a
protective device in the Load Bank, will guard against some of these
problems. If protective circuitry prevents application of the load,
determine the source of the problem. DO NOT DISABLE the
AIRFLOWorOVERTEMPERATURE SWITCHES. This will cause
a safety hazard and will void our warranty. The following
installation instructions are critical to the safe operation of the Load
Bank. Refer to the SAFETY CONSIDERATIONS section of this
manual.
*************************************************************
LOCATION
The Load Bank must be used in a cool, well ventilated area. It must be installed where cool air is
continually available and where hot exhaust air will not be recirculated through the Load Bank. If
the Load Bank is operated in a closed space, ventilation of 60,000 CFM or greater is required.
Exhaust temperature can exceed 280in approximately 3 minutes without the proper ventilation.
The exhaust air may be in excess of 280F under full load conditions. The unit must not be installed
near any equipment, wiring, or plumbing which may be damaged by high air temperatures or which
may constitute a fire hazard. Care should also be taken so as not to set off a sprinkler system by
exposing it to hot exhaust air.

Installation ASCO 4900 Outdoor Resistive Load Bank • Part Number 1251794
3-2
Do not install the Load Bank in any area where standing water can pool or accumulate. Do not
install near: a drainage basin, surface/ground or roof runoff, sewer collection, or any location where
water can back up or collect. If flooding can occur, we recommend a different location or raised
platform sufficiently above high water level. Do not operate if any portion of the Load Bank is
submerged. Always install above grade.
The Load Bank should be mounted outdoors in a free field. A prerequisite to approval of site
location is to read the next section titled AIRFLOW CONSIDERATIONS. If the installation
dictates mounting in close proximity to any external or adjacent device, transformer, generator set,
building, structure or protuberance, follow these guidelines:
1. Position the Load Bank with a minimum of 36 inches of clearance on both sides. This is in
line with the airflow to allow access for service (Figure 3-1).
2. The inlet requires a free unobstructed hemispherical zone. The radius of this sphere must be
at least 6 feet. Refer to Figure 3-1. If a unit is backed into a corner, the 6 feet is no longer
sufficient. Consult ASCO Engineering to review prior to installation. The intake must not
ingest heated air from another source. The maximum ambient intake air temperature is
120F.
3. Provide a minimum of 8 feet from any obstruction for exhaust clearance to prevent air
restrictions and to limit air recirculation. For thermal considerations, provide a minimum
clearance of 30 feet from any temperature sensitive object. The heated exhaust air stream
will damage temperature sensitive items if they are positioned within the 30 foot clearance
area. Refer to Figure 3-1.
4. Load Banks mounted into a channel, trough, hollow, well, pit, or exhausting into a full wall
or corner require special considerations even if the above conditions are met. In these cases,
provide detailed site layout drawings to ASCO for inspection and comments.
5. Locations which have full or partial perimeter fence necessitate a review. The fencing
material should have at least 75% open area. The 36" minimum side clearances shown in
Figure 3-1 still apply. Clearance on intake and exhaust can be adjusted only after approval
by an authorized ASCO representative. Painted or plated metal chain link fence is the
preferred material. All nonmetallic fencing materials are not recommended.

Installation ASCO 4900 Outdoor Resistive Load Bank • Part Number 1251794
3-3
Figure 3-1. Load Bank Installation Airflow Clearance Requirements
ADDITIONAL LOCATION NOTES
1. Do not stack, tier, or layer Load Banks without ASCO approval, as air recirculation will
occur.
2. Indoor installations will always require review. Make up air must be by a supplemental air
moving device. The Load Bank cooling system cannot be used for any purpose other than
cooling the Load Bank.
3. In northern climates with snow depths exceeding 6 inches, a physical inspection of the Load
Bank intake and exhaust is required prior to operation. Any significant snow drifts or snow
depths must be cleared prior to operation.
4. Standard Load Banks are designed for operation between sea level and 2,000 feet maximum
altitudes. Operation at altitudes over 2,000 feet above sea level requires special
consideration. Contact ASCO for assistance.
5. In general, these guidelines also apply to portable or trailer mounted Load Banks.
FAILURE TO FOLLOW THESE GUIDELINES WILL VOID THE WARRANTY.
AIRFLOW CONSIDERATIONS
Even with an ample supply of cooling air, the Load Bank may overheat if it is not properly installed.
There are two types of airflow problems that should be avoided:

Installation ASCO 4900 Outdoor Resistive Load Bank • Part Number 1251794
3-4
1. Recirculating Airflow - If the hot, exhausted air is permitted to recirculate through the Load
Bank, it will reach such a high temperature and low density that it will no longer cool the
elements. A Load Bank should not be installed so close to any surface as to reflect the
exhausted air back to the air intake. When two or more Load Banks are being used, care
must be taken in positioning the Load Banks so that the exhausted air of one unit does not
feed the air intake of another. If a Load Bank is to be mounted on a raised structure, a shield
must be incorporated in the structure to prevent exhaust air from being drawn back under the
unit.
2. Restriction of Cooling Air - Any obstruction located within the outlined parameters listed in
the previous LOCATION section of the manual will restrict the Load Bank’s airflow. Do
not modify louvers or screens on intake and exhaust. Ducting or diverting of airflow will
increase system airflow resistance and will void the warranty. If ducting is mandatory,
obtain written approval from ASCO prior to installation. Airflow is also restricted when two
or more Load Banks have air inlets positioned close to each other. This competition for
cooling air causes a low pressure area, restricting adequate airflow.
When operating a Load Bank outdoors, the wind can work for or against the Load Bank cooling
system. If the Load Bank is positioned with the prevailing wind opposing the airflow from the
blowers, inadequate cooling may result and damage to the Load Bank can occur. Improper
positioning may also result in the air switches being deactivated, thus dropping the load.
ENCLOSURE HEATERS
Each section in the Load Bank containing control components has a 100 watt strip heater and a
temperature switch. This heater may be used to prevent problems caused by condensation.
The strip heaters are powered from an externally supplied 120 VAC, 1 PH, 60 Hz source. Refer to
the Load Bank schematic diagram.
LOCAL CONTROL PANEL
The local control panel is mounted to the lower access panel covering the lower resistor assemblies
on the right side of the Load Bank (when facing the intake) and is wired to the Load Bank.
The control circuit operates from a 120V, single phase, 60 Hz, 15 amp source that is derived from
the main load bus from a 3000 VA, 480/120V control transformer.

Installation ASCO 4900 Outdoor Resistive Load Bank • Part Number 1251794
3-5
FAN/BLOWER MOTOR CONNECTION
The fan/blower circuit consists of fuses, a motor starter contactor, an overload relay, and the fan
motor. The blower input power connections are wired to TB2(1-3) located on the relay panel
assembly and are then wired directly to the main Load Bank bus.
Required power for the blower motor is 480V, 3-phase, 60 Hz, 42 amps/phase.
Make sure that the correct phase rotation is wired to the fan motor. Improper phase rotation will
cause the fan to run in the reverse direction. The cooling air should be pushed from the fan, across
the resistor elements, and out the top exhaust hood/duct. This phase rotation check is mandatory
each time the source or fan connections are changed.
If external 480 volt power is provided, safe practice dictates that the fan power be wired through a
safety disconnect switch that can be locked out.
LOAD CONNECTIONS
Quick connect cam-lok style connectors are installed on the outside corner of the Load Bank frame.
All nine connections per phase and the three ground connections must be made prior to applying any
load. The connectors are provided with mating connectors. Use these mating connectors on
interconnection load cable. Interconnection cable (by others) should be 4/0 cable.
*************************************************************
W A R N I N G
Cam-lok style connectors are factory-wired internally to theloadbus
within the Load Bank. Unused connections will be live. It is
mandatory to use all nine connections per phase. Any exposed
connection requires a factory-provided protective cap be installed.
Any lost, damaged, or heat stressed cam-lok style connector or cover
must be replaced prior to use. Failure to follow these precautions
may result in death or injury to personnel.
*************************************************************
The ampacities of these load connections are shown on schematic diagram..
After installation/connections are complete, verify proper phase to phase clearances on all load
wiring, bus bar, and hardware. Adjust or insulate to suit if required.

Installation ASCO 4900 Outdoor Resistive Load Bank • Part Number 1251794
3-6
GROUNDING
A permanent ground conductor must be connected to the Load Bank enclosure by an individual
ground wire to prevent a potential above ground on the enclosure. There is a ground nut in the Load
Bank, located within the control compartment, for this connection. This ground conductor shouldbe
run with the load power conductors to provide the lowest impedance fault path. The ground must be
connected to both the power source frame and to a good earth ground. The ground conductor should
be sized per the National Electrical Code Table 250.122, if not superseded by local codes.
INSTALLATION CHECKOUT PROCEDURE -
TO BE DONE PRIOR TO OPERATION
This Installation Checkout Procedure is intended to be used upon initial receipt of equipment and
following any relocation of a permanent mounted Load Bank. These procedures apply to Load
Banks in general and may include steps not relevant to the specific unit being installed. Disregard
those procedures which do not apply.
*************************************************************
W A R N I N G
THE FOLLOWING TESTS ARE TO BE ACCOMPLISHED BY A
QUALIFIED ELECTRICIAN OR TECHNICIAN USING
EXTREME CAUTION AS POTENTIALLY LETHAL VOLTAGES
ANDDANGEROUSROTATINGCOMPONENTS ARE PRESENT.
IF ASSISTANCE IS REQUIRED, ASCO CAN PROVIDE START
UP SERVICE AT A NOMINAL CHARGE. ASCO ALSO WILL
PROVIDE TELEPHONE ASSISTANCE IF REQUIRED BY
CALLING [phone].
*************************************************************
1. Verify the Load Bank placement meets the installation requirements found in the
INSTALLATION section of the instruction manual:
A. Check the clearance from both intake and exhaust to any obstruction.

Installation ASCO 4900 Outdoor Resistive Load Bank • Part Number 1251794
3-7
B. If the location has a prevailing wind, make the wind aid in the cooling of the resistor
elements.
C. If the Load Bank is elevated, a plate under the Load Bank will be needed to block hot
exhaust from returning to the intake.
D. Remove louver travel/storage covers.
2. Check the mechanical integrity of all customer-supplied interconnection wiring:
A. Ensure lugs are properly crimped. On units supplied with cam-lok mating
connectors, these devices must be used. On K975A 994213 unit, the mating
connector cam-lok devices which are factory supplied must be used.
B. Check terminations that they are properly torqued.
3. Utilize system schematics to ohmout customer-supplied interconnection control wiring and
safety circuits:
A. If control wiring is all the same color, ohm out each individual wire to confirm
proper labeling and placement.
C A U T I O N
Control wiring must be a minimum of 14 AWG for wire runs
under 50 feet. Consult ASCO, for wire sizing when wire run
exceeds 50 feet.
B. Confirm the correct wire gauge has been used for interconnection wiring. Control
wiring should be a minimum of 14 AWG for control panel to Load Bank lengths of
50 feet or less. For lengths greater than 50 feet, consult ASCO.
C. If a Control Transformer is the source of control power, disconnect the control
transformer before proceeding.

Installation ASCO 4900 Outdoor Resistive Load Bank • Part Number 1251794
3-8
C A U T I O N
When control power is supplied by a transformer within the
Load Bank, it must be disconnected before running this
installation checkout procedure. Failure to disconnect the
control transformer may damage the Load Bank.
4. Energize the source of control power only:
A. Check the control voltage and confirm it is within 10% of the required voltage.
*************************************************************
W A R N I N G
Control power is present on terminal block in steps 4 through 6.
*************************************************************
B. Operate the safety circuitry with a jumper across the air switch contact at its
termination at the terminal block.
5. Turn on the POWER switch and verify the proper relays energize with each individual load
switch.
A. Turn on each load step individually and observe that each relay (or relays) pulls in
without chatter or hesitation.
B. Turn on all the load steps. If chatter or hesitation is observed, locate the cause of the
voltage drop causing the problem.
6. While the load relays are energized, remove the jumper across the air switch. All the load
contactors should drop out as soon as the jumper is removed. Leave the jumperoff theair
switch.
7. Apply the rated fan voltage. Start blower and verify that air is exiting the resistor assembly
end.

Installation ASCO 4900 Outdoor Resistive Load Bank • Part Number 1251794
3-9
This checkout procedure is intended to be a guide to Load Bank installations in general. Special
installation considerations not addressed herein may be necessary due to installation site or
environment. Any questions or concerns regarding Load Bank installation should be directed to
ASCO Field Service at [phone].

Operation ASCO 4900 Outdoor Resistive Load Bank • Part Number 1251794
4-1
SECTION IV
OPERATION
Refer to the Intelligent Handheld Terminal (IHT) Quickstart Guide for operation of the Load Bank.
*************************************************************
C A U T I O N
DO NOT operate the Load Bank over the rated voltage as this will
cause catastrophic failure in the Load Bank.
Do not apply DC voltages as the contactors do not have arc blowout
magnets. Also, the reactive load sections will react as low impedance
short circuit paths, resulting in a definite fire hazard.
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*************************************************************
C A U T I O N
The operation of the blower is vital to the safe operation of this Load
Bank. When the BLOWER is turned ON, the AIR FAILURE light
will come on momentarily until the blower accelerates up to its
operating speed, at which time the light will go off.
If the air switch prevents the load from being applied (AIRFAILURE
indicator light on), do not bypass the air switch. This will cause the
Load Bank to burn up. Do not attempt to operate the unit until the
problem is corrected. Refer to the SAFETY CONSIDERATIONS
section of this manual.
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