excessive moisture being collected in the purge unit of a low-pressure refrigeration system could indicate which probable condition?
leaking condenser or chiller tubes
moisture in a refrigeration system can cause which of the following conditions?
freezing the expansion valve closed, hermetic burner blowout, and corrosion of system piping.
all the above
if the combination moisture indicator and sight glass indicates an accumulation of moisture within the system, which of the listed procedures would be the most practical to follow?
close the king valve, pump down the system, isolate the drier, remove the desiccant core, and replace the new drier cartridge.
what is a quick method used to test a water-cooled condenser for the presence of a refrigerant leak without actually pinpointing the actual location?
check the drains on the condenser heads with a halide torch.
some chlorinated fluorocarbon refrigerants may decompose into a toxic irritating gas under what conditions?
exposed to an open flame or hot surface
what must be done to use standard leak detection methods on a low-pressure refrigeration system charged with refrigerant?
raise the pressure in the system above atmospheric
to test for a suspected large refrigerant leak from an R-22 refrigeration system in an enclosed area , how should this be done?
apply a soap solution to fittings seen to have oil residue
which of the following statements is true concerning the testing of an R-22 refrigeration system for leaks in an enclosed compartment with a halide torch?
halide torches are useful in locating very small R-22 leaks
what is the color of a flame produced by a halide torch when there is no halogenated refrigerant present at the location of the exploring tube
blue
moisture is removed from recovered refrigerant using a recycling machine by what means?
circulating the refrigerant through a dehydrator
what must be done, at a minimum, before a system can legally be opened up for repairs while adhering to the prohibition against the venting of halogenated fluorocarbon refrigerants to the atmosphere?
recovery of the refrigerant
in a refrigeration system,the push-pull technique can be used for the recovery of the refrigerant in what state?
both liquid and vapor
in reclaiming recovered refrigerant, which type of contamination will the reclamation process be unable to separate?
mixed refrigerants
when removing the primary refrigerant from a system using water as a secondary refrigerant, it is important to follow which procedure(s) to safeguard the equipment?
insure the water is drained or continually circulating to avoid freeze-up.
what is the correct color-coding of refrigerant recovery cylinders regardless of the refrigerant contained within?
yellow top and grey body
A "hydroscopic" lubricant used in a refrigeration compressors would have what characteristic?
having a high affinity for moisture which requires it to be kept in a sealed container
what is the most important consideration in selecting a lubricating oil for use in a refrigeration compressor?
have a low pour point
the lubrication oil in the crankcase of a refrigeration compressor thats shutdown is heated. for what purpose is this done?
reduce absorption of refrigerant by the oil
when checking the oil level in a refrigeration compressor, under what conditions would the most accurate reading be obtained?
several minutes after shutdown, following a prolonged period of operation.
what is the color-coding for a storage container of R-134a refrigerant?
light blue
when a relief valve opens on a refrigeration compressor discharge line, it discharges high pressure refrigerant vapor to what location?
suction side of the compressor
if passive recovery is used on a small appliance fitted with a capillary tube as a metering device with a non-operating compressor, the recovery should be made through what means?
recovery from both high and low sides
which of the fluids listed is suitable for use as a secondary refrigerant?
brine
which of the following refrigerants is chlorine free and safe regarding atmospheric ozone depletion?
R-134a
traditionally, which of the listed refrigerants has been more suitable than the others for use in a centrifugal refrigeration compressor?
R-11
the amount of HCFC-123 in a storage cylinder is measured by what means?
weight
loss of refrigerant during the process of purging of air and non-condensable gases can be kept to a minimum by what action
cracking the purge valve briefly and allowing the refrigerant to re-settle between purges.
before charging a refrigeration unit, unless quick disconnect fittings are used, the refrigerant charging hoses should be prepared in what way?
they should be purged with refrigerant
which of the following statements describes the accepted method for testing a thermostatic expansion valve?
place the sensing bulb in ice watering then warm by hand. observe the flood-through and temperature change at the suction line.
a small obstruction at the thermostatic expansion valve inlet will result in which of the following conditions?
lower than normal suction pressure.
if the superheat setting of the thermostatic expansion valve is set to low, what would be the result, assuming that the system has a single evaporator?
the suction line will be abnormally cold and liquid may flood back to the compressor.
if the superheat value of the thermostatic expansion valve is adjusted too high, what would be the result?
the suction line of the compressor would be abnormally warm.
what is true concerning frost build-up on the evaporator coils of a multi-box direct expansion refrigeration system?
the frost can be removed by passing hot gas through the coils or energizing defrost heaters with the evaporator fan shut down.
the term 'oil foaming' in refrigeration practice, is used to describe what event?
release of miscible refrigerant from the lubricant in the crank case.
the "tare weight" of a refrigerant storage cylinder refers to what weight?
the weight of an empty cylinder.
what is one function of the thermal expansion valve used in a refrigeration system?
regulate the amount of refrigerant flow to the evaporator coil.
a thermal expansion valve installed in a refrigeration system is controlled by the action of what device?
the TEV sensing bulb mounted on the evaporator tail coil.
when the sensing bulb of a thermostatic expansion valve is charged with a fluid different from the charge used in the system, what name of the charge is associated with the power element?
cross charged
besides the evaporator pressure, the thermal expansion valve reacts directly to changes in what parameter?
temperature of the evaporator coil outlet.
in a refrigeration system with multiple evaporators, the metering of refrigerant to each refrigerated space evaporator is accomplished by what device?
the individual thermal expansion valves.
rather than design an infinite variety of thermostatic expansion valve sizes to accommodate different capacities for heat removal, some manufactures use a few standard valve body sizes in conjunction with what other feature?
internal needle valve offices of various sizes to accommodate different heat removal capacities.
in a refrigeration system, the bulb for the thermal expansion valve is always located where?
at the evaporator coil outlet.
which of the valves listed is normally closed when charging the refrigeration system through the high side?
liquid line king valve.
in a refrigeration plant, what is one vital purpose of the receiver?
store the refrigerant charge
the receiver used in a refrigeration system preforms what essential function?
holds the entire refrigerant charge after system pump down.
a liquid sight flow indicator in a refrigeration system is examined and gas bubbles are noted in motion with the fluid flow. what does this mean?
the system contains less than a full charge of refrigerant.
when a refrigeration compressor motor fails to start, the FIRST thing that should be checked for is what?
blown fuse or tripped circuit breaker in the motor circuit.
a refrigeration system is equipped with a reciprocating compressor and water-cooled condensing unit. if the system is overcharged, the resulting high head pressure will be caused by what condition?
refrigerant flooding the condenser.
one cause of high head pressure occurring in a refrigeration system can be which of the following?
insufficient cooling water to the condenser.
excessive prolonged oil foaming in the crankcase of a refrigeration compressor can result in what condition?
overheated compressor bearings.
which of the following conditions would indicate that the liquid line strainer in a refrigeration system has become excessively restricted and requires cleaning or replacement?
noticeable temperature drop between the strainer inlet and the outlet tubing.
during test to discover why a refrigeration compressor is running continuously, it is determined the the refrigerated space temperature is slightly above normal without ever reaching the desired minimum temperature. suction and discharge pressures are nor
leaking door gaskets.
an increasing head pressure in a refrigeration system, without any corresponding change in the cooling water inlet temperature, would probably be cause by which of the following?
air and non-condensable gases in the condenser.
the compressor is heard to knock while pumping down the low side for repairs, but otherwise the compressor sounds normal; this is a possible indication of what condition?
foaming of the crankcase oil.
if refrigeration system compressor crankcase is exhibiting an unusual degree of sweating or frosting and is operating noisily, what should be done?
check the evaporator superheat.
if increasing the cooling water flow to a refrigeration condenser fails to lower the condenser pressure, the probable cause may be due to what condition?
excessive amount of non-condensable gasses trapped in the condenser.
refrigeration systems using forced air circulation evaporators have a tendency to cause rapid dehydration of produce in chill boxes, which of the following will minimize dehydration?
the air is circulated slowly over a large evaporator with a minimum temperature differential.
the thermostat controlling the operation of the solenoid valve to a refrigerated box evaporator senses what temperature?
the refrigerated box temperature
which of the listed operations will cause an automatically controlled refrigeration compressor to restart if the system features a pump down cycle?
an increase in the suction pressure.
what is the purpose of the low-pressure cut-out switch as used as a primary controller for a refrigeration system or unit?
start and stop the compressor as needed.
in a refrigeration system featuring low-side pump down prior to the automatic shutdown of the compressor, the temperature of the refrigerated space is controlled by the action of a thermostat wired to what device?
liquid line box solenoid.
how does a refrigeration solenoid valve differ from a modulating valve?
a liquid line solenoid valve is either completely opened or closed, whereas a modulating valve is infinitely positioned according to the strength of the applied electrical signal.
the sensing line for the low-pressure cutout switch for a refrigeration system is typically connected at what location?
at the suction side of the compressor.
in a multi-evaporator refrigeration system, a solenoid valve is installed in the liquid line prior to what device?
each expansion valve.
which of the precautions listed should be taken before opening any part of a refrigeration system for the purpose of accomplishing non-major repairs?
bring part of the system to be opened to 0psig.
for safe storage, the maximum allowable temperature to which refrigerant bottles should be exposed is what temperature?
125 degrees F
personnel servicing refrigeration systems and subject to the exposure to commonly used refrigerants should wear what type of personal protective equipment?
googles and gloves.
Overfilling a refrigerant container is extremely dangerous because of the high pressures generated. The generation of pressure is the result of what?
hydrostatic pressure of the expanding liquid.
In the presence of an open flame or hot surfaces, chlorinated fluorocarbon refrigerants decompose and form what chemical substance?
phosgene gas.
Why can CFC or HCFC refrigerants leaking into a confined space or in limited surroundings cause suffocation?
Refrigerants are heavier than air and displace oxygen.
Excessively tight drive belts installed between a motor and a refrigeration compressor pulley may cause what condition?
premature wear of both the pulley end motor shaft bearing and the pulley end compressor crankshaft main bearing due to overloading
When one belt of a multiple V-belt drive requires replacing, what will be required?
replace the entire belt set.
When installing a mechanical shaft seal on a refrigeration compressor, extreme care must be taken to prevent what from happening?
dirt and foreign particles from coming in contact with the highly polished sealing surfaces.
In addition to the drive belt itself, a V-belt that is tensioned too tight will cause excessive wear to what other drive component?
motor shaft and compressor main bearings.
If the discharge reed valves used in a refrigeration compressor are leaking badly, what statement is true?
the reed valves should be replaced.
Which of the conditions listed may be an indication of an excessive amount of refrigerant circulating through the system?
Sweating of the compressor crankcase.
An evaporator coil of a single evaporator, air-cooled refrigerator is accumulating excessive frost due to a failure of the defrost mechanism. If the refrigerator features a thermostatically controlled box solenoid and a low-pressure cutout controlled comp
short cycle on low-pressure cutout.
Concerning the operation of refrigeration systems, frosting or sweating of a liquid line is usually indicative of what condition?
a liquid line restriction.
If an abnormally large difference is maintained between the evaporator refrigerant temperature and the box air temperature within the refrigerated compartment, what will be the result?
the evaporator coil will tend to excessively frost.
If the refrigeration compressor crankcase is sweating or frosting and is operating with an unusual noise, what is most likely the cause?
liquid refrigerant returning to the compressor.
If a refrigeration system, equipped with a reciprocating compressor, has a liquid line solenoid valve that is leaking during the 'off' cycle, what would this cause?
noisy compressor operation upon starting.
If a refrigeration system were short of refrigerant, besides an elevated box temperature, what would be an observable symptom?
continuous running of the compressor.
If the running suction pressure at the refrigeration compressor of a TXV controlled air- cooled refrigeration system is below normal, which of the following can be a cause?
a restricted liquid line strainer.
The color and/or condition of the oil observed in the sight glass of an operating refrigeration compressor experiencing bearing wear or piston scoring would be which of the following?
gray or metallic.
Leaking suction valves in a refrigeration compressor are indicated by which of the following?
higher than normal suction pressure.
A refrigeration unit will tend to short cycle when operating under what conditions?
lack of refrigerant.
An excessive charge of refrigerant in a thermostatically controlled, air-cooled, refrigeration system using a TXV as an expansion device can cause which of the following?
higher than normal discharge pressure.
Which of the listed statements describes the reason why oil foaming occurs when starting a refrigeration compressor?
This condition is the result of the sudden low-pressure created in the crankcase at start up causing the release of refrigerant absorbed within the oil.
When a refrigeration compressor has developed a high head pressure as a result of a refrigerant overcharge, what should be done to compensate for or to correct this situation?
remove some refrigerant from the system.
A reciprocating refrigeration compressor may be tested for leaking discharge valves by stopping the compressor, turning the discharge service valve all the way in, and then turning the compressor over by hand. If the discharge valves are leaking, the comp
rising and falling with each stroke.
Unusual noise coming from a refrigeration compressor can be caused by which of the following conditions?
worn bearings and piston pins, slugging due to flooding back, too much oil in circulation.
all of the above
Capacity control of a centrifugal refrigeration compressor can be accomplished by what means?
varying the speed of the compressor, varying the position of the suction inlet damper vanes, varying the position of the hot gas bypass valve.
all of the above.
A refrigeration compressor used in a multi-box refrigeration system is designed with six of its eight cylinders able to be controlled for variable load conditions. If all of the reefer boxes are currently feeding, what percentage of the total number of co
100%
On a modern refrigerated container unit employing suction modulation for the purposes of capacity control and capacity limitation, what happens when the applied voltage and current draw associated with the normally open (NO) suction modulation valve locat
the valve will further close, raising evaporator pressure and lowering suction pressure
Minor repairs may be performed on low-pressure refrigerant systems without recovering the refrigerant charge if the pressure in the system is raised to atmospheric. How may this be accomplished?
heat the refrigerant.
The most cost-effective method of recovering refrigerant from a low-pressure chiller with more than 500 lbs of refrigerant and to meet EPA requirements is to recover the refrigerant using what protocol?
liquid recovery using a liquid pump, followed by vapor recovery using a vacuum pump based recovery unit.
If the evaporator coil horizontal return line of a container refrigeration system is less than 0.875" (2.21 cm) in diameter (considered small); the thermostatic expansion valve sensing bulb should be attached where on the return line?
on the upper surface of the line.
When replacing a thermostatic expansion valve power element, what is true concerning the thermal bulb?
with steel wool or an abrasive cloth remove oxidation on the bulb and suction line.
When starting a reciprocating refrigeration compressor that has been shut down for a period of time, you should manually throttle which valve?
suction valve.
A device used to hold open the refrigeration compressor suction valve during starting to reduce the compression load is called what?
cylinder unloader
When opening or closing compressor service and line isolation valves on a typical refrigeration system that is fitted with packed valves, what must you do?
you must first remove the stem seal cap
The safety heads of most large reciprocating compressors used in refrigeration systems are held in place by what means?
heavy coil springs
Technicians servicing small refrigeration appliances can employ what type of recovery equipment?
either active or passive
What is true concerning highly contaminated refrigerant recovered from burned out small appliances?
The recovered refrigerant should be sent to a designated reclamation facility for processing.
For most multi-box refrigeration systems, the refrigerant sight glass would be located where in the system?
after the receiver in the liquid line.
Standard filter/driers used in many commercial type refrigeration units may contain what type of substance?
activated alumina or silica gel desiccant beads.
A liquid indicator sight glass is useful in determining whether or not a refrigeration system is sufficiently charged. Where is it generally located in the system?
high-pressure liquid line.
In a refrigeration system, silica gel is found in what component?
dehydrator or combination filter/drier.
Which of the devices listed will indicate whether or not a refrigeration system's dehydrator continues to be capable of removing moisture from the circulating refrigerant?
Liquid line moisture indicating sight glass.
The primary purpose of the liquid line strainer used in a refrigeration system is to prevent dirt and scale from entering what system component(s)?
thermal expansion valves.
Why are dehydrators usually located in the liquid line of refrigeration systems?
prevent icing of the expansion valve.
At ambient temperature and atmospheric pressure, what is the status of R-134a?
odorless gas
What is the physical state and pressure condition of refrigerant as it leaves a receiver in a typical refrigeration system?
high-pressure liquid.
Refrigerant entering the compressor of a refrigeration system should be in which of the following conditions?
Low-pressure vapor
Regarding heat transfer principles, which of the following are true?
Heat transfer always flows from hot regions to cold regions.
In a low-pressure refrigeration system, excessive running of the purge recovery unit generally indicates which probable condition?
system leaks on the low side.
in a low-pressure centrifugal chiller, what is meant by the term 'high efficiency purge unit?'
Those purge units which discharge very little refrigerant with the air being removed.
If a condenser coil of an air-cooled container refrigeration system becomes dirty and requires cleaning, what would be an acceptable method of cleaning?
high-pressure water wash.