phase 9 final review
Which of the following variables should be checked before a technician decides what the systems trouble is?
Suction pressure and head pressure, Superheat, subcooling and the moisture indicator of the refrigerant, The temperature of the evaporator, liquid line, and the suction line
When using a clamp on ammeter to check current draw on a given electrical load, be sure to _____.
clamp around only one of the load's wires
The most relevant measurement to make after restarting a compressor that has cycled off due to overload is _____.
compressor current draw
If there is a lack of refrigerant in a system, each pound of refrigerant will not completely ____
condense on the high side
True or False When a system is undercharged, the total amount of latent heat absorbed into the evaporator refrigerant is increased over what an adequately charged system would absorb.
false
When a technician determines that an ice machines condenser water circuit has a thin layer of mineral deposits, the technician should _____.
flush the water circuit with a scale remover
Evaporator pressure regulators (EPR's) are known by these other names, except for _____.
open on rise of differential pressure (ORD) valve
The term condenser capacity generally refers to _____.
the amount of heat a condenser can reject
If an expansion valve is stuck open _____.
the inlet screen may need to be replaced
The best and most precise way to ensure a proper refrigerant charge is to _____.
weigh in the exact prescribed amount
When there is a restriction in the high side, the TXV will respond by opening _____.
wider to allow in more refrigerant to lower the superheat.
The best position in which a solenoid valve should be mounted is _____
with the coil on top and the valve level
When leak testing a newly installed system using nitrogen, the pressure relief valve should be adjusted to open _____ above the recommended testing pressure
1 psi to 2 psi
The K-value and C-value for a material is equal when the material is exactly _____ thick.
1"
For vertical risers in the suction line, the refrigerant velocity is normally between _____.
1000 fpm and 1500 fpm
Water flow through a water cooled condenser should be adjusted so the temperature rise of the water does not exceed a _____ rise.
15 degree F
Pressure and temperature measurements on an evaporator often reveal symptoms that are the fault of the following except for the _____.
Evaporator
Systems that include manifold valves usually have multiple _____.
Evaporators
An ice machine with a vertical cube evaporator senses when to switch from refrigeration cycle to harvest cycle by use of a (n)_____.
ice thickness sensor
When servicing a single compressor, do not start the unit without having a fully functioning _____ in the circuit.
overload cut-out device
When setting aside unused tubing overnight, be sure to _____.
secure plugs or caps over the ends
Before checking whether the proper voltage is available at a specific component, be sure to _____.
set your meter to the proper setting
A small view port installed on the liquid line describes _____.
sight glass
Refrigeration systems that are site engineered are essentially _____ engineered.
site
Hard-drawn ACR tubing should be supported by clamps or brackets every _____ Feet.
six to eight
The most common way of driving a compressor in a refrigerated trailer when the trailer is idle is power from _____.
the electrical grid
A hot(not just warm) liquid line indicates that _____.
the refrigerant has not condensed or subcooled.
Stirling cycle is a closed cycle that can convert _____ and vise versa.
thermal energy into mechanical energy
True or False; Simply measuring low-side pressure at the suction service valve reveals suction line restrictions or pressure drops
False
True or False; When performing an ice capacity check on an ice machine with a water cooled condense, the ambient air temperature should be measured and recorded.
False
true or false ; Adding liquid refrigerant directly into the liquid receiver is best done with the compressor running
False
true or false ; CPVC cement should be used to join Schedule 40 PVC pipe.
False
true or false ; Copper water tubing is basically the same as copper ACR tubing, so technicians can safely use either tubing interchangeably for either purpose,
False
true or false ; Low-pressure vapor nitrogen absorbs heat from the conditioned space as it condenses into low-pressure nitrogen.
False
true or false ; Most starting relays can be and often are rebuilt in an HVACR shop for later reuse.
False
true or false ; The cooling capacity of a modulating refrigeration system is adjusted merely by turning the sysyetem off.
False
true or false ; Thermocouples are engineered to move heat when electric current is applied.
False
true or false ;In all circumstances, bubbles in the liquid line indicate an insufficient charge in the system.
False
It is important to maintain high humidity in rooms where food is cured and stored, because this _____.
allows meat to better maintain its taste and weight
true or false; When the cold air in the refrigerated space spills out through the bottom of the door opening, warmer room air move into the refrigerated space.
True
In a single commercial refrigeration system that controls two different evaporators at different temperatures _____.
an EPR valve is used on the evaporator at the higher temperature
If a unit using a capillary tube as its metering device produces insufficient refrigeration and is running continuously, most likely _____.
an undercharge of refrigerant is the cause
Airflow through a direct expansion evaporator can be checked with A(n) _____.
anemometer
When an evaporator is mounted vertically, the evaporator outlet should be located _____ the inlet.
below
A system specifically designed to reduce the temperature of cooked food to frozen storage temperature is a _____.
blast freezer
The degree of superheat is the difference between the refrigerants evaporating temperature and the temperature of the vapor at the _____ inlet
compressor
A high pressure motor control is connected to the _____.
compressor outlet
The four major components of a mechanical refrigeration system are _____
compressor, evaporator, metering device and condenser
A low ambient control valve is a combination of which two pressure regulators?
condenser and receiver
A liquid line receiver is located between between the _____ that is used for refrigerant storage after a pump down.
condenser coil and liquid line
Liquid refrigerant migration from the condenser to the compressor is possible during the off cycle when the _____.
condenser is warmer than the compressor
The number of units between when a device begins operation and ceases operation is its _____.
differential
A thermostat is most likely to cause a system to short cycle because its _____.
differential is too small
A hot gas defrost valve directs refrigerant into the low side from the _____.
discharge line
A device used to maintain proper refrigerant quality is the_____.
filter drier
In commercial refrigeration systems, a sight glass should be installed between the _____.
filter-drier and the metering device
Excessive pressure drop can cause _____ in a liquid line.
flash gas
The refrigerant that immediately vaporizes as it passes through the metering device is referred to as _____
flash gas
The temperature of a conditioned space in a secondary loop system is primarily controlld by _____.
fluid flow
A safe installation includes having a motor's _____ grounded
frame
A low-pressure control is likely to short cycle on a compressor when a _____ is leaking.
thermostatic expansion valve
Heat leakage into a refrigerated cabinet will increase as the cabinet wall _____
thickness decreases
Sweating or frosting on the suction line beyond a TXV's sensing bulb likely indicates _____
too much refrigerant flow
An air outlet or inlet that is _____ will result in inadequate cooling and abnormal temperatures and pressures.
too small
In order for a system to operate correctly, the high side of the system must have enough
vapor pumped into the condenser at the correct pressure and temperature ,heat removed from the compressor, vapor space (heat transfer surface area) in the condenser
The ideal superheat setting is when a TXV's sensing bulb temperature _____.
varies the least while the compressor is running
An effective way of ensuring that a TXV's sensing bulb is not affected by ambient air is to _____.
wrap the sensing bulb in insulation
The nominal size of water copper tubing is _____ than its outside diameter,
1/8" less
A pipe's strength is based on its wall thickness, which is called pipe _____.
schedule
The suction line should be sized so that the maximum pressure drop is equal to a saturation temperature drop of _____ degrees F.
2
A multiple-evaporator refrigeration system should have a pressure drop that is no more than _____.
2 psi
A commercial system's total heat load represents the amount of heat that the system must remove in a (n) _____ -hour period.
24
According to the US Department of Agriculture, hot foods must be cooled down to _____ after four hours.
41 Degrees F
Per FDA requirements, Food storage equipment should maintain food temperatures at or below _____ at all times.
41 F (5 C)
The minimum radius for a tubing bend is _____ times the diameter of the tubing.
5
For horizontal suction lines, the refrigerant velocity is normally between _____.
500 fpm and 700 fpm
According to the US Department of Agriculture, hot foods must be cooled down to _____after two hours.
70 F
Tubing should always be cut at an angle of _____.
90 degrees
On a multiple-evaporator refrigeration system, different temperatures are maintained in the different evaporators primarily because of the proper operation of _____.
EPR's
true or false ; A high ambient temperature causes a condensing unit to operate less efficiently.
True
Which position should the suction service valve be in during low-side charging?
Mid-position
How does excessive head pressure electrically affect refrigeration systems?
It causes the compressor to draw more current
How does excessive head pressure affect subcooling?
It decreases subcooling
true or false ; Dry ice is sometimes used as an expendable refrigerant.
True
true or false ; Due to the labor involved, it is more time consuming to install a split system than a package system
True
Which of the following statements regarding an undercharged TXV system is false?
More heat than normal will be transfered to the high side.
Medium-temperature and high-temperature refrigeration systems used in trucks and trailers typically use _____.
R-134A
Low-temperature and medium temperature refrigeration systems used in trucks and trailers typically use _____.
R-404A
true or false ; The motors of the compressors used in a compound system must be capable of starting under load.
True
How does ambient temperature affect the amount of heat an air-cooled condenser can reject?
The higher the ambient temperature the less heat it can reject.
How does surface area affect the amount of heat a condenser can reject?
The more surface area, the more heat it can reject.
true or false; Hard-drawn ACR tubing must be connected by brazing, because hard-drawn tubing cannot be flared.
True
The internal protection device in a three phase motor will open_____.
all three phases
A starved evaporator would likely be caused by the following problems except for _____.
a TXV's sensing bulb not being in contact with the suction line
Faulty motor controls may be responsible for _____.
a compressor that short cycles, a compressor that will not start, a continuously running motor
If a compressor motor cycles off due to an internal overload, operation can begin again after _____.
a cool-down period
An EPR installed with the intention of maintaining its evaporator at _____ the suction line.
a higher pressure than
If temperature measurements at the condenser outlet tubing and the end of the liquid line are significantly different, the problem is most likely _____.
a restriction in the liquid line
Food freezers use a temperature alarm system to warn that temperature has reached _____.
above an upper safe limit
As a fluids pressure decreases, it can _____.
absorb heat, expand to fill a larger volume and absorb heat, expand to fill a larger volume
When oil has been removed from a compressor, it should be tested for _____.
acidity and contamination
The thickness of ice cubes formed in a vertical evaporator ice machine is reduced by _____.
adjusting the ice thickness sensor
The most common noncondensable that gets trapped in a system is _____.
air
For air-cooling evaporators, the heat must pass through a(n) _____ on the evaporator tubing.
air film
Dry ice is composed of frozen solid _____.
carbon dioxide
A valve that allows refrigerant to flow in only one direction is a _____.
check
The most common type of tubing used in refrigeration systems is ______.
copper
The condition value at which a device begins to operate is its _____,
cut-in
The condition value at which a device ceases to operate is it _____.
cut-out
When determining a suction lines pressure drop, it is necessary to take pressure measurements _____.
downstream of the EPR
Commercial compressors often permit sampling and removal of oil through the use of an oil sump or _____.
drain
Leaks in secondary loops are easy to detect because the fluid is _____.
dyed
Concerning a commercial refrigeration system with multiple evaporators, _____.
each evaporator has its own thermostatic expansion valve
A thin, rectangular tank connecting an evaporator surrounded by a solution that freezes at a desired temperature is a (n) _____
eutectic plate
In a multiple evaporator system, a(n) _____ should be included between the suction line manifold and the outlet of the warmest evaporator.
evaporator pressure regulator
If a technician inspecting a multiple evaporator refrigeration system compared two pressure measurements (one taken from an evaporator with an EPR and one taken from an evaporator without an EPR), most likely the _____.
evaporator with an EPR would have higher pressure measurement
Relief valves are generally used to protect against high _____.
head pressure
The greater the _____, the lower the volumetric efficiency.
head pressure
The total amount of heat that leaks through the walls, windows, ceiling, and floor of the cabinet per unit frame time(usually 24 hours)describes the _____
heat leakage load
Commercial refrigeration systems must be tested under pressure on the _____ and be free of leaks.
high side and the low side
An inefficient compressor is most likely the cause of a system exhibiting _____.
high suction pressure and low head pressure
A refrigeration system with a restriction in its TXV is likely to exhibit _____.
high superheat
A refrigeration system with a restriction in its capillary tube is likely to exhibit _____.
high superheat
In a commercial refrigeration system with two evaporators, one of the evaporators must maintain a _____ in order to maintain a higher temperature than the other evaporator.
higher pressure
As head pressure rises in an ice machine with a water-cooled condenser, the water valve should _____.
increase water flow
When a compressor compresses refrigerant vapor, it decreases the volume of vapor, which in turn _____ of the vapor.
increases both temperature and pressure
On a compressor motor that is in good working order, the normal winding resistance readings are usually _____.
infinity
In commercial refrigeration, an air curtain is used to _____.
isolate a conditioned space
To cool a condenser using sea water, many boats use a (n) _____ which runs the condenser tubing outside the hull to take advantage of seawater's ability to absorb heat.
keel cooler
When troubleshooting a system that is not operating properly, use a _____ diagram.
ladder
Heat leakage into a refrigerated cabinet increases the _____ its exterior area is.
larger
If a restriction on the high side occurs at the inlet to the liquid receiver, then the system will exhibit the following except _____.
low subcooling
Two important principles of installation that help to minimize hazards are durability and _____.
neatness
The type of torch flame that is the most efficient to use when brazing is the _____ flame.
neutral
When installing a new commercial system, a standing pressure test involves pressurizing the system with _____ and letting it stand for 24 hours.
nitrogen
High head pressures in an air-cooled condenser may be caused by _____.
noncondensables in the system
If a refrigeration system will not cycle on, check compressor winding resistance using a(n) _____.
ohmmeter with power disconnected
Concerning any refrigeration system using a hermetic compressor, its _____ should be tested for acidity.
oil
When there is a very light and steady load and only a small amount of heat to move in a multiple-compressor system, then _____.
only one compressor runs
A quick way of locating possible unintentional pressure drops along a liquid line is by _____.
performing a temperature survey
The required voltage in a start winding necessary to energize a potential relay coil is called _____ voltage.
pickup
To know the color of wiring running from devices in a unit, use a _____ diagram.
pictoiral
For larger flow applications, a refrigeration system may use a(n) _____ valve.
pilot-operated
In a secondary loop refrigeration system, the secondary loop is built with _____.
plastic piping
To reduce the load on a bulk milk cooler, fresh milk is often passed through a (n)______
plate heat exchanger
The set of numbers between and including cut-in and cut-out values is a device's _____.
range
The best option for pulleys that are causing noise is to be _____.
realigned
If head pressure is within a manufacturers recommended range but condenser water drain temperature is lower than normal, the system is showing signs of heat transfer that is _____.
reduced between high-side refrigerant and condenser water
A primary benefit of minimizing the distance between the separate parts of a commercial refrigeration system is a significant reduction of _____.
refrigerant charge
If a refrigeration system's condenser contains noncondensables, then head pressure will _____ after the system cycles off.
remain constant for several minutes
Part of the service heat load includes removing _____ heat from fresh vegetables and meat.
respiration
On a multiple-evaporator refrigeration system,a _____ should be included in each liquid line leading to each TXV.
solenoid valve
The least complicated type of hot gas valve functions like a(n) _____
solenoid valve
Two plastic pipes can be joined through a process called _____ welding, which allows the surface polymers of each pipe to dissolve and become entangled.
solvent
Install a _____ to protect a compressor after a burnout.
suction line filter drier
The primary purpose of a suction line in a commercial refrigeration system is to transport a steady strean of low-pressure _____.
superheated vapor refrigerant
If a leak is determined to be in a brazed joint, _____.
take it apart, reassemble it, and braze it
Standards for wiring and electrical equipment are most often covered by _____.
the NEC
True or False; If the inside of refrigerated cabinet is cooler than the air outside of the cabinet, heat from the surrounding air will tend transfer through the materials of the cabinet to the space inside.
true
True or False; Total heat of rejection comprises the total heat load for the system and the energy added to the refrigerant by the compressor.
true
The three factors that determine the capacity of a compressor are the following except _____.
type of lubricant
If a condensing unit is placed indoors, the room must be _____.
well ventilated
If a technician took measurements that indicated that an evaporator was maintaining a cooler than normal temperature, the reason could be that the evaporators _____.
EPR is leaking
If the weight of the calculated daily ice production is within _____ of the manufacturers recommendations, the machine is operating correctly.
10%
If a technician took measurements that indicated that an evaporator was rather warmer than normal, the reason could be that the evaporator.s _____
EPR is stuck shut
how does excessive head pressure affect condenser temperature?
It raises condenser temperature
How does excessive heat pressure affect the temperature of the refrigerant fed to the refrigerant metering device?
It raises its temperature
In an overcharged system using a TXV, the _____.
TXV will meter refrigerant into the the evaporator based on superheat
Which of the following statements regarding moisture in a commercial system is false?
The color of the moisture indicator changes primarily with the variance in temperature and pressure
True or False; Controllers used with EEV's usually have a self-diagnostic function with codes specific to each manufacturer.
True
True or False; When performing an ice capacity check on an ice machine, the technician must time the ice production cycle.
True
Generally, the liquid line in a refrigeration system should _____.
be the same size as the liquid receiver service valve connection connection
The most common trouble of the shaded-pole motors used to drive fans is worn _____.
bearings
The primary danger of acidity to a hermetic compressor is _____.
breakdown of windings insulation
If a refrigeration system with a capillary tube as its refrigerant metering device has a restriction on its high side, the restriction will most likely be at the _____.
capillary tube inlet
A major concern for electrical wiring for refrigeration systems is that the wires must be large enough in order to _____.
carry the necessary amount of current
A low-side restriction will _____.
cause refrigerant to accumulate in the evaporator
If a filter-drier is clogged it will feel _____
cooler than normal
The purpose of an anti-short cycle control is to prevent the compressor from _____ before a preset time has passed.
cycling on
If a technician inspecting a multiple-evaporator refrigeration system noticed that an evaporator with an EPR was operating at a higher temperature than an evaporator without an EPR, it would appear that _____.
everything seems to be operating properly
Erratic refrigeration and constant oil slugging or pumping most likely indicates _____ in the system.
exess oil
if a solenoid valve is sticking, the technician should _____ the body of the valve to see whether this action allows hot gas to flow.
gently rap
If a restriction on the high side occurs somewhere along the liquid line, then the system will exhibit the following except _____.
higher than normal head pressure
A refrigeration system with a very dirty evaporator will mostly exhibit _____.
low suction pressure and low head pressure
In an undercharged TXV system, suction pressure will be _____.
lower than normal
A motor winding insulation test is best done using a(n) _____.
megohmmeter
The simplest fix for a system with a restricted TXV that does not involve opening the refrigeration circuit involves _____
melting any ice in the TXV
A solenoid valve with dirty or loose electrical contacts is likely to _____.
prevent the generation of enough electromagnetism to actuate the valve
The placement of a TXV's bulb is based on the _____.
size of the suction line
When a compressor has become inefficient, _____.
some compressor vapor is pushed back into the low side through leaking valves
Most EEV's use a _____ to move and position the valve's plunger.
stepper motor
The primary purpose of a liquid line in a commercial refrigeration system is to deliver a steady stream of high-pressure _____.
subcooled liquid refrigerant
An overcharged system using a capillary tube as it refrigerant metering device will exhibit low
superheat
If time and circumstances do not permit a technician to perform the superheat/subcooling methods, the refrigerant charge can be quickly checked by monitoring suction pressure, head pressure, and liquid line's _____.
sweating
To avoid overlooking details, a commercial refrigeration system should be inspected in a _____ manner.
systematic
A noisy external motor should prompt a technician to check pulley bearing _____ to determine whether the bearings should be lubricated or replaced.
temperature
If there is a significant temperature difference between each tube connected to a hot-gas defrost valve during defrost operation, then _____.
the hot gas valve may be stuck closed
True or False Most commercial compressors have an oil sump and oil drain to permit oil sampling and removal.
true
True or False; Most commercial air-cooled condensers can be cleaned by a high pressure jet of air, high-pressure water with detergent, mechanical scrubbing, or a vacuum cleaner.
true
true or false; Certain problems in flake ice machines can be easily heard due to the number of mechanical parts.
true
true or false; One indication of excess water flow is a continuous flow of water during the Off cycle in a water-cooled condenser.
true
Once the rubber isolation absorbers of a condensing unit become brittle, the unit will _____.
vibrate disagreeably
A motor that is exhibiting excessive end play can be remedied using _____.
washers
A very noisy condition in which a single, distinct thump(rap) is heard in the pipes just as a valve closes describes the term _____.
water hammer
To check head pressure of an ice machine with a water cooled condense, the manufacturer usually provides a value that correlates with what temperature measurement?
water leaving the condenser
The following checks should be done on many open-drive compressors, except for
water level
An ice machines water will develop a strong mineral concentration when the _____ drain becomes clogged.
water reservoir
An external motor's sheave should be checked using a(n) _____.
wear gauge
