WorksheetsUA Star Part 1.1
Total questions: 96
Worksheet time: 48mins
An unrepaired leak will cause which of the following conditions?
high head pressure
high subcooling
high superheat
low superheat
If mechanical refrigeration and a cooling coil are used dehumidification, the system may require which of the following?
High limit control
recooling
reheat
zero voltage switching
Which is the response when dirty filters in an air conditioning system reduce the quantity of air flowing over the DX coil?
the compressor will compensate for the change
the condenser will compensate for the change
the system capacity will decrease
the system capacity will increase
In an air-cooled system with capacity control, compressor unloading will cause which of the following to happen?
discharge pressure will rise, and energy consumption will decrease
suction pressure in discharge pressure will fall
suction pressure will fall, and energy consumption will decrease
suction pressure will rise, and discharge pressure will fall
Which is the only acceptable refrigerant to be used as a trace gas when checking for leaks?
R11
R12
R22
R500
After January 2019, what is the acceptable annual leak rate of a comfort cooling system if this circuit contains more than 50lbs of refrigerant?
25%
35%
40%
For what purpose is a cold trap installed in a series with a vacuum pump?
cool the vacuum pump oil
permit a pressure below 100 microns to be developed
reduce the rate at which water vapor is drawn into the vacuum pump's oil
reduce the systems deep vacuum requirement
When recovering “bad” R-12 and R-22, how or where should it be stored?
a used disposable cylinder
an ARI 700 cylinder
an ISO guideline cylinder
an ARI 720 cylinder
What is cleaning refrigerants to ARI 700 standards called?
reclaiming
recovering
recycling
reuse
How often should the oil in a vacuum pump be changed?
after 100 hours or when oil starts to bubble
after the vacuum pump can no longer achieve desired vacuum level
annually
the oil should only be changed when it is no longer clear
Which of the following DOT designations would be acceptable to use on a recovery cylinder when recovering R410a?
4BA200
4BA300
4BW275
4BW400
What is the best way to drive refrigerant from a cylinder into a unit being charged?
heat the cylinder with a flame
immerse the cylinder in warm water
set the cylinder on the top of a hot plate
warm the cylinder in an oven
Incorrect rotation of a scroll compressor will cause which of these events?
broken valves
excessive discharge pressure
liquid slugging
tripping of the compressor's internal protector
A hermetic compressor internal overload senses which of the following?
an overcharge of refrigerant
compressor motor temperature
excessively high pressure
low side refrigerant temperature
What is the purpose of pulling a system into a proper vacuum?
make it easier for refrigerant to be charged in the system
make it easier for refrigerant to flow in the system
remove air and non condensable in the system
remove particulate contaminants
Which of these is true of three phase alternating current?
the currents are 60 cycles apart
the currents are out of phase by 120 electrical degrees
the currents cancel each other out
the currents have no fixed relationship to one another
What happens to the current when the voltage goes up?
decreases
goes to zero
increases
remains the same
Worn sleeve bearings can be quickly checked by which of these methods?
check the centrifugal switch points
check the squirrel-cage rotor
check the stator
try to move the shaft at right angles to the bearings
What does a pillow block allow a bearing to do?
be self aligning
resist high temperature
handle light loads
set direction of fans
The word ________ is used to describe the amount of wobble on a rotating shaft as read by an indicator.
alignment
backlash
runout
none of the above
Which is the correct tool for removing bearings without damaging the shaft?
ball ping hammer
bearing puller
pipe wrench
sledgehammer
Which is the final step in installing a pillow block bearing?
align bearings
align shaft
tighten bearings to the frame
tighten bearings to the shaft
Which of these are the most important parts of a mechanical seal?
drive collars
elastomers
mating seal faces
springs
While lubricating large electric motors, the relief plug should be?
left out to allow for moisture drainage
removed
replaced with a greased fitting
tightened
Which of the following is not a cause of premature V-belt failure?
improper alignment
improper belt tension
rotation of motor
slipping
What should you do to increase airflow on a variable pitch pulley installed on the drive side?
decrease diameter
increase diameter
loosen belt tension
use a larger belt to increase distance between two shafts
After replacing belts and sheaves, which of the following does not need to be checked as a part of start up?
alignment
current draw
tightening of belt
torque of pillow block bearings
For maximum life expectancy of bearings, the pulley should be installed where?
anywhere on the shaft
as close to the bearing as possible
farthest from bearing
in the middle of the shaft
Which of the following is NOT an efficient method for aligning a single belt drive?
Laser alignment
Straight edge
string alignment
visual alignment
When checking for shaft alignment on a motor or a pump, which part of the dial indicator is placed against the shaft?
Bezel
contact point
dial face
swivel
What is the first step of shaft alignment of an open drive compressor?
angular
parallel
radial
perpendicular
Dial indicator measurements are in ________ inch increments.
.001
.101
¼
½
What is an acceptable shaft runout on a 5-horsepower electric motor?
.001"
.025"
.375"
.5"
Which of the following types of coupling require the most critical alignment?
flexible
rigid
Roller chain
Shaft
Which of the following types of couplings requires a minimum alignment?
Flexible
Rigid
Roller Chain
Shaft
Which step should be taken before replacing or installing couplings with electric motors?
Drain the pump casing
Grease the motor bearings
Lockout and tag out the motor
Lubricate the hold-down bolts
Which is the device used in electrical circuits to prevent damage from current overloads?
Fuse
Overload detector
Switch
Thermistor
What is the maximum safe amperage draw of the secondary winding of a 40 v-a transformer output of 25 volts?
7 amps
1.2 amps
1.6 amps
2.8 amps
Which is the acceptable voltage drop across an energized contactor?
0 volts
5 volts
10 volts
15 volts
How would one reverse rotation of a 3-phase motor?
Reverse any 2 power leads
Reverse leads on start capacitor
Reverse terminals number 3 and number 8
Rotate brushes
Which of the following devices changes energy from one form to another?
Transducer
Transformer
Transistor
Vacuum tube
A PSC motor has more starting torque than which of the following?
CSR
CSIR
Shaded pole motor
3 phase motor
A 3 phase motor to be used with a part-winding starter must have ______ windings?
2
3
4
6
Which is applicable when replacing defective circuit boards?
Replace with a compatible board with all jumpers and switches in proper position
Replace with a similar board
Switch with any other board available
Take one out of a machine next to it
When troubleshooting a control board you find there is no control power. Which of these is most likely the cause?
Bad relay
Bad resistor
Blown control fuse
Dirty filter
When trouble shooting 480v 3-phase starters at approximately what voltage should you find phase to phase?
240v
277v
480v
1/3 of total voltage
What is the meaning of closed transition starting?
The machine is started with inlet vanes closed
The motor is never disconnected from the line during starting
The motor is only temporarily disconnected during startup
The starter has timed-closed circuits
As compared to across the line starters, reduced voltage starters reduce _______?
Accelerating time
Inertial loads
Starting current inrush
Starting torque required
Why is a surge suppressor used on a contactor coil?
For a faster and smoother start
To prevent damage to the control circuit
To prevent damage when contacts close
To smooth out circuit wave forms
Contactors contain which two sets of contacts?
DC and AC
High voltage and low voltage
Pilot and line voltage
Stationary and moveable
Why should terminal screw be retightened on a contactor?
It increases voltage and gives lower current flow
It prevents voltage drop and high current overheating wire
Tightening screws has no effect on current
start capacitor open
While troubleshooting an HVAC system, if the voltage across a potential relay's contacts remains at 0 volts even when the compressor cycles on its internal overload, what could be a possible reason?
Closed (welded) contacts in the potential relay
Expansion valve stuck closed
Open contacts in the potential relay
Start capacitor open
When the motor of a two-wire spring return actuator is operating the spring, what is the spring doing?
Helps the motor to turn
Is being wound
Is temporarily disconnected
Opens the cam operated switch
When using a magnehelic to set up or calibrate a velocity controller, to which port or ports do you connect?
Both low and high pressure ports
High pressure port
Low pressure port
It does not matter
Which of the following is the most common instrument used to verify flow of a pump?
Auxiliary contacts
Differential pressure switch
Manometer
Paddle switch
Outdoor reset of hot water temperature for heating provides which of the following options?
Hottest water during milder weather
Hottest water during coldest weather
Hottest water only in the morning
Night set back
The symbol shown here is used to indicate which type of switch?
Flow
Pressure actuated
Spring loaded
Temperature actuated
A bourdon tube is used for which type of measurement?
Electrical resistance
Humidity
Pressure
Temperature
Which type of gauge reads pressure both above and below atmospheric pressure?
Compound
Micron
Test pressure
Vacuum
Which of these devices does NOT sense temperature?
Infrared thermometer
photoeye
RTD
Thermocouple
Operation of the flame rectification combustion control system is based on which of these principles?
A. A flame will conduct electrical current
B. Gas flames are harder to see than oil flames
C. Light travels faster than heat
D. Ultraviolet flames are harder to sense
How should safety controls be wired?
A. Across the line
B. In parallel with operating controls
C. In series with operating controls
D. Independently of other controls
The oil pressure safety control operates on which 2 pressures in the refrigeration system?
A. Discharge pressure only
B. Oil pump discharge pressure and discharge pressure
C. Oil pump discharge pressure and suction pressure
D. Suction pressure and discharge pressure
A pneumatic thermostat must be selected for a normally closed chilled water valve. Which type of action will the thermostat have?
A. Delayed response
B. Direct acting
C. Reverse acting
D. Single acting
Which of the following is a digital output?
A. Fan status
B. Humidity sensor
C. Lighting control
D. VFD spd control
Which of the following is NOT a digital input?
A. Condensate float switch
B. Fan status
C. Space temperature
D. VFD fault alarm
Which of these control modes does NOT provide modulating control?
A. Derivative
B. Integral
C. Proportional
D. 2 position
Why should low water cut off controls on a steam boiler be blown down routinely?
A. Brings clean water into the steam boiler
B. Makes room for boiler water chemical
C. Prevents sediment build up that would limit proper operation
D. None of the above
Suction gas temperature minus saturated suction temperature is equal to?
condensing temperature
evaporator operating temperature
superheat
subcooling
The boiling point of refrigerant in the condenser is the same as which of these?
compressor suction pressure
condensing temperature
discharge pressure
evaporator temperature
Which is the correct term for a coil using a TXV capillary tube or restrictor?
adiabatic
balanced
direct expansion coil (DX coil)
transverse
In what form does refrigerant leave the expansion valve?
a mixture of liquid and saturated vapor
a mixture of liquid and superheated vapor
a subcooled liquid
a superheated vapor
The purpose of taking a pressure drop reading across a suction line filter dryer is to determine the _____?
contaminated loading of the filter dryer
proper size and change
superheat readings
None of the above
What results when you reduce water flow to a water-cooled condenser?
a decrease in condenser pressure
an increase in the temperature difference between entering and leaving water
an increase in condenser capacity
a decrease in the temperature difference between entering and leaving water
Which of these should be used when chemically cleaning a water-cooled condenser?
a hydrochloric acid solution
an inhibited acid
hydrochloric acid
uninhibited acid
An evaporative cooling tower's bleed rate is adjusted to maintain which of the following?
A water seal in the drain line trap
Return water temperature
The desired concentration of total dissolved solids
The desired leaving water temperature
Which is NOT an acceptable way for capacity control on a cooling tower?
Basin heater
3 way valves
2 speed fan
VFDs
A customer would like all of their HCFC R-22 equipment retrofitted to HFC refrigerants. Which of the following refrigerants would be an acceptable replacement?
MP-39
R-12
R-134A
R-407C
Which of the following oils is the most hygroscopic?
Alkyl-benzene
Mineral oil
Petroleum base oils
Polyester oil
Which is a proper way to check the rotation on a screw compressor?
Calculate amp draw
Perform a bump check
Use a phase rotation meter
It is not necessary to check rotation on a screw compressor
Which of the following is NOT an acceptable way for capacity control of a centrifugal compressor?
Modulating diffuser vane
Liquid line solenoid valve
Modulating inlet guide vanes
VFD
Which device is used to protect a large condenser against excessive compressor discharge pressure?
Fusible plug
Magnetic check valve
Ruptured disk
Spring loaded pressure relief valve
When calculating superheat for an HFC refrigerant with a large temperature glide using a pressure/temperature chart, which column on the chart is used?
Bubble point
Dew point
Saturation point
Wet bulb temperature
What is a disadvantage of a variable refrigerant flow (VRF) system?
Does not allow for future expansion
Flexible capacity control
Increased capacity
Increased installation cost
Which of the following is true of natural gas?
It has a natural odor of its own
It has a sweet, pleasant odor
It has an odor added to it to make it detectable
It has no chance of leaking into a boiler room
When is the pilot light on in an intermittent pilot system?
During post-purge
During pre-purge
Only during the pilot trial for ignition
Throughout the main flame cycle
Most appliance gas valves require inlet natural gas pressure NOT to exceed which measurement?
1 psi
3.5" wc
14" wc
28" wc
What is the name for the safety control that shuts down a furnace or other gas heating devices when the plenum temperature exceeds the design of the system?
Fan switch
High limit switch
Thermocouple
Thermostat
1 watt = 3.413 btu/hr. A 30 kw electric heater will produce how many btu's per hour in this space?
102.3 btu/h
2838 btu/h
30,000
While working on a make-up air unit, what may have caused the unit to shut down if the customer notifies you that their direct-fired process equipment has just shut down?
A. A timer has shut off the equipment
B. The low ambient temperature has shut off the unit
C. The thermostat is not satisfied
D. There is an open interlock between the MAU and the process equipment
Which of the following is a cause leading to premature heat exchanger failures on gas-fired units?
A. Clogged air filters and loose fan belts
B. High air flow from supply fan
C. High outside air temperature
D. Low btu content of natural gas
In a high-pressure steam boiler, which of the following is controlled by surface blowdown?
A. Sediments
B. Flue stack temperatures
C. Total dissolved solids
D. Remove scale
Low pressure steam boilers are classified as those having operating pressures below how many psi?
A. 15 psi
B. 30 psi
C. 50 psi
D. 100 psi
You should use which of these devices to protect large condeners agasit excessive compressor discharge
Either a fusible plug or ruptured disk
Fusible plug
magnetic check valve
Spring loaded pressure relief valve
A constant __________ is maintained by the txv
Coil pressure
Coil Temperature
Expansion rate
Super heat
Which is the fast way to recover refrigerant?
Liquid only recovery
Vacuum pump only recovery
Push and pull method
Vapor only recovery
