WorksheetsStudy Assistant E (MowExE)
Total questions: 177
Worksheet time: 6hrs 54mins
Where is refrigerant vapour charged into a system?
Liquid line.
Condensate line.
Hot gas line.
Suction line.
What is used in a system which has an evaporator equipped with a distributor?
Crankcase pressure regulating valve.
Externally equalized thermostatic expansion valve.
Evaporator pressure regulating valve.
Internally equalized thermostatic expansion valve.
Which operating condition applies to start windings in split phase motors?
Out of phase with the run winding.
Always disconnected from the circuit.
In phase with the run winding.
Never disconnected from the circuit.
A condensing unit requires 6 lb. - 8 oz.; the evaporator requires 2 oz.; the line set is 50 feet long, the liquid line contains 0.48 oz. per foot; and the suction line contains 0.10 oz. per foot. What is the required system charge?
9 lb. - 9 oz
8 lb. - 5 oz
9 lb. - 4 oz
8 lb. - 7 oz
What happens when the bulb temperature of a maximum operating pressure (MOP) thermostatic expansion valve rises above a maximum point?
Pressure stops rising quickly, then rises extremely slowly.
Pressure stops rising, then decreases due to adsorption.
Pressure stops rising, then decreases due to condensation.
Pressure stops rising, then rises suddenly and bursts the bulb.
How are refrigerant suction lines sloped?
Against direction of flow.
Away from the compressor.
Towards the evaporator.
With direction of flow.
What is the function of a compressor crankcase heater?
Boils vapour refrigerant out of the oil.
Warms the oil to ensure it flows easily.
Minimize refrigerant migration to the compressor.
Reduce the viscosity of the oil.
What is indicated by a discolored electrical connection?
Faulty electrical connection.
Excessive amount of moisture present.
Short circuit in the system.
Insulation has broken down.
Which position are the cylinder valves in, when the piston is approaching the bottom of its stroke in a reciprocating compressor?
Suction valve open, discharge valve closed.
Suction valve open, discharge valve open.
Suction valve closed, discharge valve open.
Suction valve closed, discharge valve closed.
When is superheat added to a refrigerant?
As it changes from a vapour to a liquid.
After all the liquid has evaporated.
When the temperature of the liquid is rising.
As it changes from a liquid to a vapour.
What is Ohm's Law?
Voltage varies directly as the square of the applied electromotive force.
Current varies directly to the applied voltage if the resistance is constant.
Current varies inversely with the resistance when the voltage is constant.
Voltage varies inversely to the current when the resistance is constant.
What is the pressure of a full acetylene tank?
500 psi
2200 psi
250 psi
1000 psi
What is the output of an electric heater that has a 240 volt supply and draws 50 amps?
1,200 kW
12 kW
12,000 kW
120 kW
In Table PT1, what is the design evaporating pressure for an R-22 comfort cooling system?
92.6 psig
54.9 psig
68.5 psig
84.0 psig
What is a British Thermal Unit (BTU)?
Heat that when added to or removed from a substance causes a change of temperature.
Amount of heat required to change the temperature of one pound of a substance by 1?F.
Heat that when added to or removed from a substance causes a change of state.
Amount of heat required to change the temperature of one pound of water by 1?F.
Which condition effects the operation of a cooling tower?
Entering air dry bulb temperature.
Entering air wet bulb temperature.
Leaving air wet bulb temperature.
Leaving air dry bulb temperature.
What is the controlling factor of a potential relay?
Current drawn in the run winding.
Current drawn in the start winding.
Back EMF across the start winding.
Back EMF across the run winding.
What does a filter remove at the inlet of a capillary tube?
Solids.
Moisture.
Excess oil.
Air.
Refer to Table PT1, what is the design evaporating pressure for an R-410A comfort cooling system?
107.5 psig
118.5 psig
142.7 psig
156.0 psig
Where is the bulb of a thermostatic expansion valve installed on a 1-1/8" OD suction line?
At a 90 degree angle from the top of the suction line.
At a 45 degree angle from the bottom of the suction line.
On the top of the suction line.
On the bottom of the suction line.
What are dirt and oxides which are trapped in welds?
Blowholes
Inclusions
Exclusions
Penetrants
In Electrical Diagram 1, what type of control is LPPD?
Operating
Proportional
Disconnect
Derivative
Which factors determine the capacitance of electrolytic capacitors?
Thickness of the plates and the type of dielectric.
Thickness and area of the dielectric and the direction of the current flow.
Area of the plates and the type of dielectric.
Area of the plates and the type and thickness of the dielectric.
In Electrical Diagram 1, what type of safety circuit is demonstrated?
Normally Open Lockout
One time pump out.
Normally Closed Lockout.
Recycling pumpdown
What is the normal position of starting relay contacts?
Current normally open, potential normally open.
Current normally closed, potential normally closed.
Current normally closed, potential normally open.
Current normally open, potential normally closed.
What is the function of isolating valves in refrigeration systems?
Protects against excessive pressure.
Reduces refrigerant loss.
Reduces pressure drop.
Protects components against freezing.
What is the primary rating of a transformer which has a turns ratio of 5 to 1 and a secondary output of 24 volts and 20 amps?
120 volts, 4 amps
240 volts, 2 amps
120 volts, 100 amps
240 volts, 50 amps
Which light rays can burn or blister eyeballs?
Visible
Infrared
Gamma
Ultraviolet
Which method is used to refill a partially discharged comfort cooling system which has a fixed orifice metering device?
Remove the remaining refrigerant and weigh-in the total system charge.
Add refrigerant until the specified superheat is obtained.
Add refrigerant until frost just appears on the suction line.
Add refrigerant until the sight glass indicates that it is full.
A 1750 rpm motor with a 4 inch pulley is driving a compressor with a 10 inch flywheel at 700 rpm. What size motor pulley is required to drive the compressor at 875 rpm?
3.2 inch diameter.
3.7 inch diameter.
4.5 inch diameter.
5.0 inch diameter.
What happens when a conductor is moved through a magnetic field?
Magnetic field collapses.
Voltage is induced in the conductor.
Magnetic field is induced in the conductor.
Current is induced in the conductor.
Why is the valve on an oxygen cylinder opened for an instant before connecting the regulator?
Blows dirt out of the tank connection.
Blows moisture out of the tank.
Ensures the cylinder is not empty.
Ensures there is no air in the tank.
How much heat is added to 10 pounds of ice at - 20F degrees to change it to water at 70 degrees F?
208 Btu
2080 Btu
1880 Btu
2340 Btu
What is the function of a cylinder regulator?
Maintains cylinder pressure to working pressure.
Raises cylinder pressure to working pressure.
Prevents torch from popping.
Prevents reverse flow of gases.
Which is caused by a loose thermostatic expansion valve bulb?
Excessive evaporator superheat.
Higher evaporator temperature.
Floodback to the compressor.
Increased liquid subcooling.
What is measured using a sling psychrometer?
Dry bulb and wet bulb temperatures.
Relative humidity and moisture content.
Air volume and velocity.
Specific volume and specific density.
Which process uses is a neutral flame?
Hard surfacing.
Brazing copper.
Searing cast iron.
Flame cutting.
When the pressure difference across a capillary tube increases, what is the effect on the refrigerant flow?
Becomes erratic.
Increases.
Decreases.
Remains the same.
Which material is used to connect a vacuum pump and micron gauge to a system?
Aluminum tubing.
Heavy duty manifold hose.
Copper tubing.
Light flexible manifold hose.
Which substance depletes stratospheric ozone?
Carbon atoms.
Hydrogen atoms.
Fluorine molecules.
Chlorine molecules.
What is the relationship between locked rotor amperage (LRA. and running current)?
LRA is 7 to 9 times greater.
LRA is 1 to 3times greater.
LRA is 4 to 6 times greater.
LRA is 10 to 12 times greater.
What is a micron?
One millionth of a meter.
One thousandth of a kilometer.
One millionth of a kilometer.
One thousandth of a meter.
What is the colour of an acetylene hose?
Green
Orange
Red
Black
What happens when a capillary tube is replaced with one of the same length but with a smaller inside diameter?
Evaporator temperature and pressure are higher and the compressor runs at a higher than normal current.
Evaporator pressure and temperature are higher and the compressor runs at a lower than normal current.
Evaporator pressure and temperature are lower and the compressor runs at a lower than normal current.
Evaporator temperature and pressure are lower and the compressor runs at a higher than normal current.
Where is the liquid line drier located?
Metering device outlet.
Condenser inlet.
Receiver outlet.
Evaporator inlet.
Which oil is used with HFC refrigerants?
Capella HD.
Alkylbenzene
Polyolester
Mineral
What is in the tube and what is in the shell of a shell and tube condenser?
Refrigerant in the tube and condensing medium in the shell.
Condensing medium in the tube and refrigerant in the shell.
Medium being cooled in the tube and evaporating medium in the shell.
Evaporating medium in the tube and medium being cooled in the shell.
When any branch circuit in a parallel network opens, what is the effect on total current?
Decreases
Fluctuates.
Increases.
Remains the same.
Which parallel combination is used as a substitute for a 330 v - 140 mfd capacitor?
220 v - 20 mfd and 550 v - 50 mfd
440 v - 180 mfd and 220 v - 80 mfd
440 v - 40 mfd and 550 v - 100 mfd
220 v - 80 mfd and 330 v - 60 mfd
Which identifies a single phase motor with only one capacitor that remains in the circuit when the motor runs?
CSR (Capacitor Start Capacitor Run).
PSC (Permanent Split Capacitor).
ISIR (Induction Start Induction Run).
CSIR (Capacitor Start Induction Run).
Which type of copper is used for refrigeration lines?
Type M-ACR.
Type G-ACR
Type DWV.
Type L-ACR
When does oil foam in a compressor?
When the head pressure becomes excessive.
When the pressure drops in the crankcase.
When moisture is trapped in the crankcase.
When there is a hydraulic slug.
Which temperature effects the operation of an air-cooled condenser?
Entering air wet bulb temperature.
Entering air dry bulb temperature.
Leaving air dry bulb temperature.
Leaving air wet bulb temperature.
What is the purpose of a compressor in a mechanical cooling system?
Raises the temperature and pressure of the refrigerant.
Raises the pressure of the liquid refrigerant and vapour.
Regulates the flow of refrigerant in the system.
Causes the refrigerant to flow in the system.
How far does a conductor extend inside a junction box?
3 inches.
6 inches.
12 inches.
9 inches.
What is the capacitance of two 20 mfd capacitors connected in series?
40 mfd
30 mfd
10 mfd
20 mfd
What is thermostat temperature differential?
Difference between the set point and the cut in point.
Difference between the room temperature and the cut out point.
Difference between the room temperature and the set point.
Difference between the cut in point and cut out point.
How is absolute pressure determined?
Atmospheric pressure minus gauge pressure.
Gauge pressure plus atmospheric pressure.
Gauge pressure minus atmospheric pressure.
Atmospheric pressure divided by gauge pressure.
What is the resistance of two 20 ohm loads connected in series?
40 ohms.
10 ohms.
20 ohms.
30 ohms.
What is the relief pressure of an oxygen cylinder valve rupture disk?
3000 psi
4200 psi
4000 psi
3200 psi
Which describes the fumes when welding galvanized steel?
Caustic.
Acidic.
Toxic.
Explosive.
What is caused by an oversized suction line?
Oil logging in the evaporator.
Excessive off cycle refrigerant migration.
Excessive oil leaving the compressor.
Liquid slugging on start up.
What is the total current flow through a 120 volt circuit, with one 10 ohm resistor in series and two 10 ohm resistors connected in parallel with each other?
8 amps.
15 amps.
4 amps.
12 amps.
How far is tubing inserted into a swaged joint?
Depth equal to ¼ times the outside diameter of the tubing.
Depth equal to ½ times the outside diameter of the tubing.
Depth equal to 1 times the outside diameter of the tubing.
Depth equal to 1 ½ times the outside diameter of the tubing.
Which wire has the largest diameter?
#12 AWG.
#8 AWG.
#14 AWG.
#10 AWG.
Which component rejects the most latent heat?
Evaporator
Compressor
Condenser
Metering device.
Refer to Diagram 1, What type is the diagram?
Connection
Pictorial
Field wiring.
Ladder (Schematic)
What happens to the capacity of an air-cooled condenser when the volume of constant temperature air decreases when passing through the condenser?
Fluctuates.
Increases.
Decreases.
Remains the same.
What is a characteristic of parallel circuits?
Current reading will be the same no matter where it is taken in the circuit.
Voltage drop across each load is less than the voltage applied to the circuit.
Total resistance of the circuit is less than the smallest resistance in the circuit.
Total resistance of the circuit is the sum of each individual resistance in the circuit.
What is the function of a pressure limiting thermostatic expansion valve?
Controls the suction pressure below a preset maximum.
Prevents overloading the compressor motor.
Maximizes the compressor capacity.
Limits the discharge pressure above a preset minimum.
What is the function of the J-tube in a suction line accumulator?
Improves oil return.
Prevents refrigerant migration.
Increases superheat.
Prevents oil return.
Which component adds the most heat to the refrigerant?
Compressor
Metering device
Suction line
Evaporator
Which values are multiplied to determine wattage in AC inductive circuits?
Voltage, amperage, and resistance.
Voltage and power.
Voltage, amperage, and power factor.
Voltage and amperage.
What is the effect on the resistance of a conductor when the temperature rises?
Fluctuates
Increases
Decreases
Remains the same
What is the "Law of Electrical Charges"?
Like charges attract, unlike charges repel.
Number of protons always equals the number of neutrons.
Number of neutrons always equals the number of electrons.
Like charges repel, unlike charges attract.
When cutting, how is regulator pressure determined?
Cylinder pressure.
Size of hose.
Type of metal.
Thickness of metal.
Where is flux applied when silver brazing?
Brazing rod.
Male and female parts.
Female parts.
Male parts.
What is the procedure for setting the cut-out pressure on a low pressure control?
Cut-out equals differential minus cut in.
Cut-out equals cut in minus differential.
Cut-out equals cut in plus range.
Cut-out equals cut in plus differential.
Which pressures are measured using a compound gauge?
Gauge and absolute.
Gauge and vacuum.
Atmospheric and specific.
Suction and discharge.
Which components make up a standard refrigeration gauge and testing manifold?
2 gauges, 2 valves, and 4 ports.
2 gauges, 2 valves, and 1 port.
2 gauges, 2 valves, and 3 ports.
2 gauges, 2 valves, and 2 ports.
What is the voltage drop across a closed switch in an energized electrical circuit?
0 volts.
120 volts.
240 volts.
2 to 5 volts.
An extension ladder placed against the side of a 20 ft. high building must open to a minimum of what length?
23 feet 8 inches
25 feet
24 feet
24 feet 8 inches
What causes some liquid refrigerant to return to a running compressor?
Insufficient evaporator superheat.
Undercharged system.
Excessive airflow through the evaporator.
Undersized metering device.
Where is a muffler installed in a refrigeration system?
Between the evaporator and the condenser.
Between the compressor and the condenser.
Between the condenser and the receiver.
Between the evaporator and the compressor.
Why is nitrogen purged through refrigerant piping during brazing?
Prevents the copper from oxidizing.
Prevents discolouration.
Reduces the risk of explosion.
Reduces exterior scale formation.
Why are liquid lines and suction lines soldered together?
Increases evaporator flash gas.
Improves compressor motor cooling.
Decreases the condensing pressure.
Cools the liquid and heats suction gas.
What is the result when some nitrogen is left in an operating R410A?
High discharge pressure.
High suction pressure.
Nitric acid forms.
Copper nitrates form.
What is the weight of a 26 lb. - 4 oz. cylinder after 30 oz. of refrigerant has been removed?
22 lb. - 8 oz
24 lb. - 6 oz
22 lb. - 4 oz
24 lb. - 4 oz
In Figure PE4, which line represents the metering device?
5 to 9
2 to 7
2 to 3
2 to 6
In Electrical Diagram 1, the compressor is short cycling during the satisfied mode, what is the problem?
Undercharge of refrigerant
LPPD setpoint is lower than LPC setpoint.
Liquid Line Solenoid valve seat is leaking.
Overcharge of refrigerant.
What happens to the capacity of a water-cooled condenser when the volume of constant-temperature water passing through the condenser is reduced?
Remains the same.
Decreases
Increases
Fluctuates
Which condition causes refrigerant flooding in a system?
Dirty condenser.
High heat load.
Refrigerant undercharge.
Dirty air filters.
Why is flux removed after joining materials?
Ensures a stronger joint.
Enables joint quality inspection.
Improves the appearance.
Prevents corrosion.
Which compressor motor uses a current relay and a start capacitor only?
ISIR (Induction Start Induction Run)
PSC (Permanent Split Capacitor)
CSIR (Capacitor Start Induction Run)
XL (Across the Line)
Which indicates a full liquid line sight glass?
Full of bubbles.
Cloudy.
Light green.
Clear.
What is the minimum flow point range of low temperature brazing alloys?
800 to 900 degrees F
400 to 600 degrees F
1,100 to 1,200 degrees F
1,400 to 1,600 degrees F
When the drier temperature drops, what is the effect on the moisture holding capacity of a liquid line drier?
Capacity remains the same.
Capacity fluctuates.
Capacity increases.
Capacity decreases.
Which term describes reprocessing recovered refrigerant by any means to meet ARI specifications?
Recovery.
Recycling.
Reclaim.
Regeneration.
What determines the resistance of a conductor?
Length, relative resistance, material, and type of insulation.
Length, material, diameter and temperature.
Length, current, material, and relative resistance.
Length, diameter, material, and type of insulation.
Refer to Diagram 1, what is the purpose of the underlined numbers on the right side of the drawing?
Location of normally open contacts.
Location of relays.
Location of loads
Location of normally closed contacts.
Which combination of conditions in a compressor crankcase allows refrigerant migration from the evaporator?
Low temperature, low pressure.
High temperature, high pressure.
Low temperature, high pressure.
High temperature, low pressure.
Which motor does not require a starting switch or mechanism?
Capacitor start.
Capacitor start, capacitor run.
Split phase.
Shaded pole.
What is latent heat?
Heat that when added to or removed from a substance causes a change of temperature.
Heat that when added to or removed from a substance causes a change of state.
Amount of heat required to change the temperature of one pound of water by 1 degrees F.
Amount of heat required to change the temperature of one pound of a substance by 1 degrees F.
How does a vacuum gauge indicate that a leak free system has moisture in it when the vacuum pump is blanked off?
Pressure rises then levels off below 5000 microns.
Pressure continues to fall.
Pressure rises, levels off then falls.
Pressure rises to atmospheric pressure.
Which tool is used to cut a capillary tube?
Hack saw.
Pipe cutter.
Triangular file.
Tube cutter.
What pressure rating is required for a R-410A recovery cylinder?
600 psi
400 psi
800 psi
500 psi
Why is flux used when brazing?
Cleans the components.
Melts the alloy at a lower temperature.
Helps the alloy bond with the molten base metal.
Reduces oxidation.
Which formula represents Boyle's law?
P1 x V1 = P2 x V2
P1 x T2 = P2 x T1
P1 x T1 = P2 x T2
P1 x V2 = P2 x V1
What is the controlling factor of a current relay?
Back EMF across the start winding.
Current drawn in the start winding.
Current drawn in the run winding.
Back EMF across the run winding.
What is the resistance of a light bulb that draws 0.9 amps at 110 volts?
122.22 ohms.
0.008 ohms.
12.22 ohms.
0.08 ohms.
Which term describes the process of cleaning refrigerant for reuse by distillation, oil separation, or multiple passes through a filter-drier?
Regeneration
Reclaim
Recycling
Recovery
When pulling a vacuum, which evacuation procedure is used?
Pull down to 5,000 microns
Evacuate from one side
Energize LLSV
Fully back-seat service valves
Which are used for measuring operating temperatures in a cooling system?
Glass stemmed thermometers containing mercury or coloured water, and electric thermometers which use bimetal elements or thermistors.
Glass stemmed thermometers containing mercury or red oil, and electric thermometers which use thermocouples or thermistors.
Glass stemmed thermometers containing mercury or coloured water, and electric thermometers which use thermocouples or thermistors.
Glass stemmed thermometers containing mercury or red oil, and electric thermometers which use bimetal elements or thermocouples.
How many tons of refrigeration are required to cool 600 pounds of water from 150 degrees F to 50 degrees F in one hour?
4 tons
5 tons
3 tons
2 ton
What are the conditions when charging a single component refrigerant through the suction service valve?
Liquid with the cylinder upside down.
Vapour with the cylinder upright.
Vapour with the cylinder upside down.
Liquid with the cylinder upright.
How much is an oxygen cylinder valve opened, when brazing?
1-1/2 turns.
1 turn.
2 turns.
Fully
What is the function of a suction line accumulator?
Increases superheat.
Prevents refrigerant migration.
Improves oil return.
Prevents running floodback.
What is used to determine the system test pressure in a built-up system?
From the system nameplate.
From the CSA B-52 mechanical refrigeration code.
Same as the saturated refrigerant pressure at 105 degrees F.
Condensing pressure plus 100 psi.
How is refrigerant removed from a 400 or 500 series refrigerant cylinder?
Vapour with the cylinder upright.
Liquid with the cylinder upright.
Liquid with the cylinder upside down.
Vapour with the cylinder upside down.
Which heat transfer fluids does an evaporative condenser use as the condensing media?
Air and water.
Water and glycol.
Water and brine.
Air and glycol.
What is the effect on total current in a series circuit when the voltage remains constant and more loads are added?
Increases
Decreases.
Fluctuates.
Remains the same.
What are the common, start, and run terminals on a single phase motor where terminals X to Y = 2 ohms, terminals Y to Z = 8 ohms, and terminals X to Z = 6 ohms?
X = Run, Y = Common, Z = Start
X = Start, Y = Run, Z = Common
X = Common, Y = Run, Z = Start
X = Common, Y = Start, Z = Run
Which piping device is at the outlet of an evaporator that is located above a compressor?
Check valve.
Equalizer.
Inverted trap.
Pee trap.
Which processes and chemicals are required for a flame?
Heat, fuel, and gas.
Fuel, air, and oxygen.
Heat, fuel, and oxygen.
Heat, air, and oxygen.
Which compressor uses a mechanical shaft seal?
Open.
Semi-hermetic.
Hermetic centrifugal.
Hermetic.
What is indicated when a charged unit is short cycling, there is a hissing sound and the liquid line is cold?
Acid in the system.
Restriction in the liquid line.
Condensing unit is undersized.
Air in the system.
What is used to cool welded hermetic compressor motor windings?
Internal fan.
Ambient air.
Water.
Suction gas.
What does a comfort cooling system remove from the conditioned space?
Specific heat and latent heat.
Latent heat and radiant heat.
Specific heat and sensible heat.
Sensible heat and latent heat.
How is a clamp-on amp meter applied?
Around one conductor.
Around two conductors.
On a de-energized circuit.
On a de-energized fuse.
Which process is used to obtain a gas tight joint when joining metal parts with alloys at over 1,000?F?
Brazed
Welded
Soldered
Fused
When brazing, which heat source directly melts the filler material?
Torch flame.
Tubing and fitting.
Flux.
Surrounding air.
In Electrical Diagram 1, What would cause the compressor to seize shortly after start up?
CFCC open.
CC auxiliary contacts are welded closed.
CFCC closed.
CC auxiliary contacts are welded open.
What is the maximum amount of refrigerant to be placed into a recovery cylinder having a tare weight of 20 lbs and a Water Capacity of 40 lbs?
24 lbs
20 lbs
32 lbs
28 lbs
What occurs when the outlet valve of a receiver is front seated while the system is operating?
High pressure control opens.
System pumps down.
Compressor is damaged.
Suction pressure increases.
What is the maximum safe working pressure for acetylene?
25 psi
10 psi
20 psi
15 psi
What is the colour of an oxygen hose?
Red
Black
Orange
Green
When is a factory installed crankcase heater energized?
When the temperature falls.
When the compressor is running.
When the temperature rises.
When the compressor is off.
Which condition is prevented by evaporator superheat?
Warm vapour returning to the compressor.
Liquid refrigerant returning to the compressor.
Frost build up on the evaporator.
Sufficient compressor motor cooling.
Which pressures control the operation of an internally equalized thermostatic expansion valve?
Difference between the evaporator pressure and the pressure corresponding to the gas temperature at the evaporator outlet.
Difference between the saturated evaporator pressure and the saturated evaporator temperature.
Difference in temperature between the gas at the evaporator inlet and the temperature of the gas leaving the evaporator.
Difference between the valve inlet pressure and the pressure corresponding to the gas temperature at the evaporator outlet.
What is the condition of a refrigerant as it leaves an expansion valve?
Saturated vapour.
Saturated liquid and vapour.
Subcooled liquid.
Subcooled liquid and vapour.
What is protected by a bleed resistor on a start capacitor?
Motor run winding.
Motor start winding.
Potential relay contacts.
Potential relay coil.
Why is copper tubing reamed before it is flared?
Prevents opposition to refrigerant flow.
Prevents excess wear due to restriction.
Ensures the flare has a uniform diameter.
Ensures the flare has a uniform thickness.
What happens to the latent heat of vapourization as the pressure on the surface of a liquid refrigerant decreases?
Decreases.
Increases.
Fluctuates.
Remains the same.
What is sensible heat?
Heat that when added to or removed from a substance causes a change of temperature.
Heat that when added to or removed from a substance causes a change of state.
Amount of heat required to change the temperature of one pound of water by 1 degrees F.
Amount of heat required to change the temperature of one pound of a substance by 1 degrees F.
What is the voltage drop across a blown fuse?
Applied voltage.
120 volts.
1 to 5 volts.
0 volts.
How is a run capacitor connected in a permanent split capacitor (PSC) motor?
Series with the start winding.
Parallel with the start winding.
Parallel with the run winding.
Series with the run winding.
What is the resistance of a blown fuse?
300 to 500 ohms.
Infinity
1,000 to 100,000 ohms.
0 ohms.
What is ambient temperature?
Indoor temperature.
Surrounding temperature.
Mixed air temperature.
Outdoor temperature.
In Electrical Diagram 1, what is the purpose of the normally open LOR contacts?
Prevent the circuit from cycling on safties
Energize the circuit if the LPPD does not close
Bypass LOR coil.
De-energize LOR coil.
Which group of components are found only in the high pressure side of a refrigeration system?
Condenser, evaporator, and discharge line.
Condenser, compressor, and metering device.
Condenser, receiver, and condensate line.
Condenser, liquid line, and metering device.
Which indicates a suction valve leak in a reciprocating compressor?
Higher than normal suction pressure when the compressor is running.
Slight hissing sound during operation.
Decrease in the vacuum when the compressor is sitting idle.
Increase in head pressure when the compressor is running.
Which shut-off valve has the least restriction to flow?
Packed angle valve.
Suction service valve.
Globe valve.
Ball valve.
What is the net oil pressure in a compressor with an oil pump outlet pressure of 65 psig and a crankcase pressure of 35 psig?
35 psig
100 psig
30 psig
65 psig
What happens when a critically charged system is overcharged?
decreased operating pressures.
Reduced metering device feed.
Increased system efficiency
Reduced discharge temperature.
To ensure dehydration is complete, how many microns does a system maintain?
800
1,000
500
200
Which substance is used for pressure testing a refrigeration system?
R-22
R-12
N2
R-134A
What results when refrigerant and moisture mix in a system?
Sulphuric acid.
Hydrofluoric acid.
Carbon dioxide.
Chlorine dioxide.
In Electrical Diagram 1, during a lock out condition, what is the voltage be across the LOR and CC coils,?
CC - zero volts, LOR - control voltage
CC - control voltage, LOR - control voltage.
CC - 18 volts, LOR - 6 volts
CC - 6 volts, LOR - 18 volts
What happens when some nitrogen is left in an operating R134a system?
Nitric acid forms.
High suction pressure.
Copper nitrates form.
High discharge pressure.
What is the volumetric efficiency of a compressor with a displacement of 15 cfm when it is actually pumping 12 cfm?
60%
80%
100%
125%
How many Btu/hr equal one horsepower of mechanical energy?
12,000 Btu/hr
746 Btu/hr
2,545 Btu/hr
3.41 Btu/hr
In Figure PE4, which line represents superheat added in the evaporator?
7 to 8
5 to 9
2 to 3
8 to 9
What is done to check the potential difference to an operating motor?
Voltmeter in series with the motor leads
Potentiometer in parallel with the motor leads
Potentiometer in series with the motor leads
Voltmeter in parallel with the motor leads
How many microns of pressure are there in a system when a compound gauge reads 29"Hg vacuum?
25,400
2,540
254
254,000
Which process is used to join a copper to steel connection?
Mechanical.
Soldered.
Welded.
Silver brazed.
Which indicates an overcharge of refrigerant?
Suction line is at saturation.
Subcooling is normal.
Suction line is superheated.
Subcooling is high.
What is the synchronous speed of a four pole motor?
Two times the speed of a two pole motor.
Four times the speed of a two pole motor.
One half the speed of a two pole motor.
One quarter the speed of a two pole motor.
What happens to the current when the voltage doubles in a resistive circuit and everything else remains the same?
Decreases by one quarter.
Increases by four times.
Increases by two times.
Decreases by one half.
In Electrical Diagram 1, what is the function of CFCC?
Maintains pressure differential across expansion valve.
Decreases head pressure during low ambient operation.
Decreases head pressure during design conditions.
Increases head pressure during design conditions.
What is the function of a liquid-to-suction heat exchanger?
Heats high side vapour.
Increases net refrigeration effect.
Cools suction vapour.
Heats liquid refrigerant.
What is the compression ratio when the head pressure is 240 psig and the suction pressure is 40 psig?
3.4:1.0
4.6:1.0
2.0:1.0
6:1.0
Which type of motor has the highest starting torque?
Induction start.
Shaded pole.
Capacitor.
Split phase.
When removing a valve plate from an open or semi-hermetic compressor, what is the position of the service valves?
Discharge valve back seated and suction valve front-seate
Discharge valve and suction valve front-seated.
Discharge valve front seated and suction valve back-seated.
Discharge valve and suction valve back-seated.
What is the function of suction line insulation in residential comfort cooling applications?
Increases superheat.
Lowers noise levels.
Ensures subcooling.
Prevents condensation.
What happens to the volume of a vapour when the pressure on the vapour is constant but the temperature above absolute zero is doubled?
Decreases by one half.
Doubles.
Is squared.
Remains the same.
What is superheat?
Heat added to a substance to change it from a liquid to a vapour.
Heat required to change one pound of a substance from a solid to a liquid.
Heat added to a substance raising its temperature above saturation.
Heat required to change one pound of a substance from a liquid to a vapour.
What is another function of a shell and tube condenser?
Separation chamber.
Receiver.
Recirculator.
Float chamber.
