Pre-Test #2

Question 1

A cubic foot of water weighs _____lbs

a) 8.333
b) 10
c) 62.4
d) 64.2

Answer 1

62.4

Question 2

A US gallon of water weighs ____lbs

a) 8.33
b) 10
c) 62.4
d) 64.2

Answer 2

a

Question 3

The specific heat of water is?

Answer 3

1

Question 4

The latent heat of fusion of water (ice) is _______btu/lb

Answer 4

144

Question 5

The latent heat of vaporization of water (steam) is _____btu/lb

Answer 5

970

Question 6

The opening force on a TXV is?

a) spring pressure
b) bulb pressure
c) suction pressure
d) head pressure

Answer 6

b) bulb pressure

Question 7

The TXV regulates refrigerant flow to the evaporator based on?

a) heat of compression
b) superheat
c) external equalization pressure

Answer 7

superheat

Question 8

An external equalizer is used when?

a) the pressure drop across the evaporator is too great
b) the liquid line pressure becomes too great
c) the receiver is too full of refrigerant
d) pressure drop at the axe is too great

Answer 8

a) pressure drop across the evaporator is too great

Question 9

When the load on the evaporator increases, the txv?

Answer 9

a) increases the flow of refrigerant

Question 10

To determine superheat with a blended refrigerant the correct formula is superheat is equal to

a) measured vapour temp minus dew point temp
b) measured vapour temperature minus bubble point temp

Answer 10

a)

Question 11

To determine superheat with an azeotropic refrigerant (no glide) the correct formula is superheat is equal to:

a) measured liquid temperature minus saturation temperature
b) measured vapour temperature minus saturation temperature

Answer 11

b)

Question 12

To determine sub-cooling with a blended refrigerant the correct formula is

a) measured liquid temp minus dew point temp
b) bubble point temp minus measured liquid

Answer 12

b)

Question 13

In the b52 code a refrigerant of A3 classification indicates

a) a toxic refrigerant that burns easily
b) a non toxic refrigerant that burns easily
c) a toxic refrigerant that cannot be burned

Answer 13

b)

Question 14

The term toxic as used in b52 refers to:

a) causes damage to surfaces
b) dangerous to use in a hermetic system
c) hazardous to human health
d) causes ozone layer damage

Answer 14

c)

Question 15

When converting R12 to R134, one must always;

a) install new filter drier
b) check txv is compatible
c) check oil
d) all of the above

Answer 15

d)

Question 16

the term glide when referring to blended refrigerants means

a) alkyl benzene oil must be used
b) temp difference between dew point and bubble point at constant temperature
c) amount of txv calibration

Answer 16

b)

Question 17

3412 btus is equal to

a) 1 watt
b) 3.4 watts
c) 1 kw
d) 3.4 kw

Answer 17

c) 1kw

Question 18

A typical heat pump will have a high pressure switch to shut the unit off if head pressure becomes high. The control action of this switch closes the contacts on a pressure:

a) rise at comp discharge
b) fall at comp discharge
c) difference between high and low side

Answer 18

b)

Question 19

Which of the following is the correct formula for determining wattage in a resistive electrical circuit?

a) W=E x I
b) W=E/I
c) W=IR

Answer 19

a

Question 20

The RPM of a motor is determined by

a) motors voltage
b) amperage
c) number of poles

Answer 20

c)

Question 21

An ohmmeter reading of infinity across switch contacts means?

a) open
b) closed
c) good
d) bad switch

Answer 21

a)

Question 22

Contractors are rated according to max amperage through the

a) coil
b) contacts
c) thermostat
d) fuse

Answer 22

b) contacts

Question 23

Lowering airflow over a coil will

a) increase temp drop and increase moisture removal
b) decrease temp drop and increase moisture removed

Answer 23

a)

Question 24

On which would the following most likely be powered by 240v single phase

a) natural gas furnace
b) residential condensing unit
c) roof top unit
d) residential humidifier

Answer 24

b)

Question 24

Which of the following would be the best place to mount a thermostat a) kitchen b) bathroom c) exterior wall d) near a return air grille

Answer 24

d)

Question 25

Condensate piping must be properly trapped to prevent a) ice formation b) condensate running off evaporator coil c) overflowing d) excessive air noise

Answer 25

d)

Question 26

Which of the following would only be used on an induced draft condensing furnace? a) electronic fan control b) hot surface ingnition c) induced draft blower motor d) secondary heat exchanger

Answer 26

d)

Question 27

Which precaution should an installer perform to keep copper from oxidizing internally while brazing? a) hold torch flame steady b) purge tube with nitrogen c) increase heat

Answer 27

b)

Question 28

Charles law states a) at constant pressure, volume of gas varies directly with absolute temp b) total pressure of a confined mixture of gasses is the sum of the pressures of each gas

Answer 28

a)

Question 29

How is compressor compression ratio determined? a) discharge psia/suction psia b) discharge pig/suction psig

Answer 29

a)

Question 30

Where in the system is the excess superheat added that must be removed before condensation in the condenser can take place? a) start of evaporator and end of receiver b) end of receiver and start of txv c) end of evaporator and in comp

Answer 30

c)

Question 31

Fresh air intakes ducts, used to route outdoor air to inside, connect to the a) vent piping b) combustion air duct c) supply side of cut d) return side of duct

Answer 31

d)

Question 32

Daltons law states a) constant pressure, the volume of gas varies with absolute temp b) total pressure of a confined mixture of gasses is the sum of the pressures of each of the gasses in the mixture

Answer 32

b)

Question 33

What are three commonly used metering devices for residential and light commercial air conditioning? a) TXV, AXV, Low side float b) high side float, low side float, cap tube c) cap tube, txv, piston type

Answer 33

c)

Question 34

The external equalizer connection to the suction line, should be located a) next to the txv sensing bulb b) 6 to 8 inches upstream from the txv sensing bulb c) 6 to 8 inches downstream from the txv sensing bulb d) none of the above

Answer 34

c)

Question 35

Which of the following refrigerants is a HCFC? a) R12 b) R22 c) R-502 d) R-134a

Answer 35

b)

Question 36

Technician arrives on a call for an air to air heat pump during heating season. He notes the system operates until defrost energizes. System stays in defrost for approx 10 min when there is no ice? a) defrost timer is defective b) defrost termination switch stuck closed c) defrost termination switch stuck open

Answer 36

c)

Question 37

What are the symptoms of an air conditioning system that has a low charge? a) evaporator coil will be partially frosted and discharge pressure will increase b) suction line will sweat and low side pressure will decrease c) low side pressure will decrease and the evaporator coil will be partially frosted

Answer 37

c)

Question 38

An AC has an inoperable blower. When the stat is set below room temperature, there is 24v across R and G. What is the problem? a) bad blower motor b) bad blower relay c) bad thermostat d) any of the above

Answer 38

c)

Question 39

With belt driven equipment, alignment of the motor and driven equipment pulleys: a) is not critical because belts flex b) accomplished using straight edge c) when belts are parallel d) using dial indicator

Answer 39

b)

Question 40

Compressor capacity controlled by cylinder unloading a) may result in compressor overheating b) used only on hermetic comp c) does not save energy

Answer 40

a)

Question 41

Most compressors are positive displacement. Name a negative

Answer 41

Centrifugal

Question 42

The ratio of actual volume of vapour pumped to the theoretical displacement volume is known as a) volumetric efficiency b) volumetric ratio c) compression efficiency

Answer 42

a)

Question 43

Compressor in which the compressor and motor are both sealed is known as?

Answer 43

hermetic

Question 44

Compressor capacity decreases as: a) discharge pressure increases b) suction pressure decreases c) compressor speed decreases d) all of the above

Answer 44

d)

Question 45

Scroll compression does what? a) vapour enters from outside and exits centre b) enters from centre and exits outside

Answer 45

a)

Question 46

Capacity control on a screw compressor is obtained using a) inlet vanes b) hot gas c) variable speed motors d) a sliding valve

Answer 46

d)

Question 47

Bearings in an operating centrifugal compressor can be checked by a) sliding the impeller back and forth to check for slop b) trying to move the shaft at right angles to bearing c) checking the temperature of the oil returning from the bearing

Answer 47

c)

Question 48

As a rule of thumb, for every 12,000btuh of cooling capacity in an open drive compressor air conditioning system, the heat rejection is roughly a) 12,000btuh or 1 times the NRE b) 9,000btuh, or .75 NRE c) 15,000btuh or 1.25 NRE

Answer 48

c)

Question 49

A decrease in condensing temperature will a) increase condensing pressure, increase suction temperature and increase capacity b) decrease condensing pressure, decrease suction temperature and increase system capacity

Answer 49

b)

Question 50

Subcooling in the condenser will a) increase system capacity b) decrease system capacity c) not affect system capacity

Answer 50

a) increase

Question 51

A possible cause of high head pressure is a) dirty condenser b) insufficient water flow c) air and non condensibles d) all

Answer 51

d)

Question 52

In order to protect a load, safety limit devices are most often wired a) parallel b) series c) upstream

Answer 52

b)

Question 53

A flow switch safety control is for a) control of amount of flow b) turn on a pump or fan c) divert fluid flow d) prove flow

Answer 53

d)

Question 54

What is a disadvantage of a mercury bulb switch a) they are unreliable b) they must be level c) they tend to burn contacts

Answer 54

b)

Question 55

A thermostat is properly calibrated when a) set point and control point are equal b) room temp is comfortable c) no dead band d) control point and thermometer are equal

Answer 55

a)

Question 56

With a change in temperature, a thermistor will change a) resistance b) voltage c) current d) impedance

Answer 56

a)

Question 57

A gauge where an increase in pressure straightens the tube a) whiskey tube b) bimetal tube c) bourdon tube

Answer 57

c)

Question 58

In a TXV, three forces act on the diaphragm in the power head, which is connected to the valve. Evaporator pressure acts to _____ the valve, spring pressure acts to ____ the valve, and the bulb pressure _____ the valve

Answer 58

close, close, open

Question 59

A common indication of a defective potential starting relay on a single phase motor is a) motor hums but does not start b) motor starts, runs normal, then shuts off c) motor runs at half of speed

Answer 59

a)

Question 60

Level of voltage created by the back EMF that opens contacts on a potential relay is called a) lift voltage b) open voltage c) run voltage d) pick-up voltage

Answer 60

d)

Question 61

As the evaporator temperature of any vapour compression system is lowered a) compressor suction vapour density increases b) volume of suction vapour decreases c) compressor capacity is lowered

Answer 61

c)

Question 62

When charging a chilled water system, charge as a liquid. However, the machine is deep in vacuum, initial charge shall be vapour. why? a) faster b) allows pressure to stabilize and prevent shock c) prevents condensation d) charge until system temp above freezing prevents freezing of water in tubes

Answer 62

d)

Question 63

A special valve used to prevent evaporator temperature from falling below a predetermined minimum temperature regardless of suction pressure is the a) EPR b) pressure reducing valve c) suction pressure regulator

Answer 63

a)

Question 64

In general, a greater number of rows in an evaporator a) air leaving closer to refrigerant b) more dehumidification c) colder the leaving air will be d) all of the above

Answer 64

d)

Question 65

Increasing air flow over an evaporator a) increases capacity b) decrease evaporator capacity c) does not affect evaporator capacity d) none of the above

Answer 65

a)

Question 66

A hermetic motor should never be energized or tested with a merger while in a deep vacuum because a) electric arcs can contaminate freon b) motor could draw too much amp c) vacuum pump could be damaged d) dielectric strength of the motors insulation would be greatly reduced

Answer 66

d)

Question 67

Term used to describe a pumps ability to draw a vacuum. Pump must create a vacuum in itself lower than the system. The point at which a pump can no longer create a pressure difference is a) dead head b) blank off c) blocked tight static d) point of no pressure difference

Answer 67

b)

Question 68

The oil pressure safety is operated by a) oil pressure alone b) sum of oil pump discharge and crankcase pressure c) difference in crankcase pressure and oil pump discharge pressure

Answer 68

c)

Question 69

In order for an oil failure control to operate correctly, it must be wired so that it gets power to the heater circuit a) all times b) only when comp running c) only when good oil pressure d) after oil change

Answer 69

b)

Question 70

When the compressor has adequate oil pressure, the contacts between L and M are?

Answer 70

closed

Question 71

Most common cause of low oil pressure is?

Answer 71

failed pump

Question 72

The coil of a current relay is open. The compressor has a start capacitor but no run capacitor. The problem noted is a) overload trips due to high current in start winding b) compressor draws no current and fails to start c) compressor starts when pressure equalizes

Answer 72

b)

Question 73

If the temperature of the air being handled by a forward curved fan is reduced substantially a) cfm increases b) static pressure increases c) cfm decreases d) motor amperage increases

Answer 73

d) amps up because the cold air is more dense causing the motor to work harder