HVAC - CH 08 - Leak Detection

A state-of-the-art electronic leak detector features an infrared sensor with what expected lifespan? A. 1 year B. 5 years C. 10 years D. Unlimited

C. 10 years. The leak detector in Figure 8.16(E) features a state-of-the-art infrared sensor with a 10-year life expectancy

After a manifold-less evacuation is completed, when should micron gauges ideally be removed from the system to prevent exposing the instrument to high pressure and potential damage? A. Immediately after the evacuation completes. B. When the system pressure is just above atmospheric pressure (2 to 3 psig), shortly after charging has started. C. After the system has been fully charged and is running. D. Only after the system has been recovered again.

B. When the system pressure is just above atmospheric pressure (2 to 3 psig), shortly after charging has started. Micron gauges should be removed from the system shortly after the charging process has been started, ideally when the system pressure is just above atmospheric pressure (2 to 3 psig)

After applying a leak detection solution to any surface of a refrigeration or air-conditioning system, what must be done to prevent oxidation, corrosion, or rust? A. Allow it to air dry completely. B. Simply wipe the area with a rag. C. Thoroughly wash the area with water. D. Apply a layer of protective paint.

C. Thoroughly wash the area with water. Care must be taken to thoroughly wash the area with water, as simply wiping will not suffice and residue can cause oxidation, corrosion, or rust

After pressurizing a system for a standing pressure test, how long should it be allowed to stand to allow pressures to equalize before observing gauges? A. 1 minute B. 5 minutes C. About 10 minutes D. 30 minutes

C. About 10 minutes. Once pressurized, the system should be allowed to stand for about 10 minutes to allow pressures in the system to equalize

After the vacuum gauge reaches the desired level and the vacuum pump is valved off, what should the instrument reading do within a very short time (about 1 minute)? A. Continue to rise indefinitely. B. Drop to zero. C. Rise for a very short time, then stabilize. D. Fluctuate wildly.

C. Rise for a very short time, then stabilize. When the vacuum reaches the desired level, the vacuum pump should be valved off, and the reading may rise for a very short time (about 1 minute), then it should stabilize

Are cumulative microleaks generally considered an acceptable amount of leakage in the industry? A. No, they always require immediate repair. B. Only if the system is less than 5 years old. C. Yes, at this time, they are considered an acceptable amount of leakage. D. Only if a trace gas is used.

C. Yes, at this time, they are considered an acceptable amount of leakage. At this time, microleaks are considered an acceptable amount of leakage in the industry

At what pressure can HFC-134a (R-134a) become combustible when mixed with air at concentrations of more than 60% air by volume? A. At pressures as low as 5.5 psig (at 350°F) B. Only at pressures above 500 psig C. Never, HFC-134a is non-combustible D. At atmospheric pressure regardless of temperature

A. At pressures as low as 5.5 psig (at 350°F). HFC-134a (R-134a) is combustible at pressures as low as 5.5 psig (at 350°F) when mixed with air at concentrations of more than 60% air by volume

Before performing a standing pressure test, what visual checks should a technician conduct on a newly assembled system? A. Check for overall system cleanliness only. B. Verify solder connections have no gaps, flanges/threaded connectors are tight, control valves are correctly installed/set, and valve covers are on. C. Confirm all electrical connections are properly insulated. D. Inspect only the compressor for proper alignment.

B. Verify solder connections have no gaps, flanges/threaded connectors are tight, control valves are correctly installed/set, and valve covers are on. The technician should perform a visual test to ensure these connections look as they should

Before testing for evaporator leaks, if the system does not have any pressure, what should be done? A. Immediately apply a microfoam solution to the coil. B. Recover any remaining refrigerant. C. Add a refrigerant trace gas and then add nitrogen to generate a practical test pressure. D. Pressurize the system with pure oxygen.

C. Add a refrigerant trace gas and then add nitrogen to generate a practical test pressure. If the system does not have any pressure, a refrigerant trace gas should be added, followed by nitrogen to create a practical test pressure

Can vacuum pumps remove solids such as sludge from a refrigeration system? A. Yes, all vacuum pumps are designed for this. B. Only if the sludge is in liquid form. C. No, vacuum pumps are not designed to remove solids; sludge and solids can only be removed by correct filtration. D. Yes, if a deep vacuum is maintained for a long period.

C. No, vacuum pumps are not designed to remove solids; sludge and solids can only be removed by correct filtration. Vacuum pumps are not designed to remove solids such as sludge, and deep vacuum procedures will not take the place of liquid-line or suction-line driers for the same reason

For removing large amounts of moisture from a system, what type of vacuum pump is recommended? A. A low CFM vacuum pump. B. A high CFM vacuum pump. C. A piston-type vacuum pump. D. A hand-operated vacuum pump.

B. A high CFM vacuum pump. It takes a large vacuum pump to pull moisture in the vapor state out of a system

For systems using R-410A, what may be the working pressure for the high-pressure side during a standing pressure test? A. 150 psig B. 250 psig C. 350 psig D. Up to 450 psig

D. Up to 450 psig. Systems using R-410A may have working pressures up to 450 psig on the high-pressure side

For systems with many valves and piping runs, what must be verified before starting evacuation to ensure complete removal of air? A. All valves are closed. B. All valves are in the open position. C. Only the main service valves are open. D. The system is completely charged.

B. All valves are in the open position. A thorough inspection should be done to ensure that all valves on the system are in the open position, especially normally closed solenoid valves that can trap air

For which types of refrigerants are halide leak detectors effective? A. Only HFC refrigerants B. Only refrigerants that contain chlorine, such as CFCs and HCFCs C. All refrigerants, including HFCs and HCs D. Only hydrocarbon (HC) refrigerants

B. Only refrigerants that contain chlorine, such as CFCs and HCFCs. The halide leak detector can only be used with refrigerants that have chlorine as part of their formula, such as CFCs and HCFCs

How can a technician differentiate between oil residue and condensate when performing an oil spotting check? A. By observing the color of the wetness. B. By smelling the residue. C. By rubbing the area with fingers and feeling for oil slickness. D. By using an electronic moisture meter.

C. By rubbing the area with fingers and feeling for oil slickness. The technician must determine whether the wetness is oil and not condensate by rubbing the area with fingers and feeling for oil slickness

How can dissolved refrigerant in a compressor's crankcase oil be released during evacuation? A. By cooling the crankcase. B. By heating the crankcase with a heat lamp or gently tapping it with a rubber hammer. C. By increasing the system pressure. D. By introducing nitrogen into the crankcase.

B. By heating the crankcase with a heat lamp or gently tapping it with a rubber hammer. Heating the crankcase with a heat lamp or gently tapping it with a rubber hammer will often cause enough heat and/or vibration to release the dissolved refrigerant

How can technicians overcome the restriction caused by Schrader valve stems during evacuation? A. By using an oversized vacuum pump. B. By removing the valve stems during evacuation and replacing them when finished using a core removal tool. C. By adding more refrigerant to increase pressure. D. By using longer gauge hoses.

B. By removing the valve stems during evacuation and replacing them when finished using a core removal tool. The valve stems and depressors act as restrictions, so removing the valve stems during evacuation and replacing them afterwards is an alternative

How can the risk of vacuum pump oil being sucked back into the refrigeration system be prevented during a power failure? A. By ensuring the vacuum pump runs continuously. B. By disconnecting the vacuum pump from the system before leaving. C. By installing a large solenoid valve in the vacuum line wired in parallel with the vacuum pump motor. D. By using a smaller vacuum pump.

C. By installing a large solenoid valve in the vacuum line wired in parallel with the vacuum pump motor. This prevents vacuum from being lost and the pump from losing lubrication if power fails

How can water trapped under the oil in a compressor's crankcase be released? A. By adding more oil to dilute it. B. By cooling the compressor. C. By breaking the oil's surface tension with vibration (e.g., tapping with a soft-face hammer) or applying heat to the crankcase. D. By continuously pulling a deep vacuum for extended periods.

C. By breaking the oil's surface tension with vibration (e.g., tapping with a soft-face hammer) or applying heat to the crankcase. The oil surface tension can be broken with vibration or applying heat to the compressor crankcase, which will release the water

How do ultraviolet (UV) fluorescent leak detectors work? A. By detecting changes in flame color. B. By listening for high-pitched sounds. C. By using a special fluorescent dye that mixes with oil and glows under black light when escaping through a leak. D. By measuring the concentration of refrigerant vapor in the air.

C. By using a special fluorescent dye that mixes with oil and glows under black light when escaping through a leak. UV fluorescent leak detectors work by means of a special fluorescent dye that is charged into the system, mixes with oil, and glows under black light when it escapes through the leak

How does moisture affect the vacuum pump sealing oil's ability to maintain a low micron seal? A. It enhances it. B. It reduces it by raising the oil's vapor pressure. C. It has no effect. D. It changes the oil's color but not its performance.

B. It reduces it by raising the oil's vapor pressure. When moisture enters the vacuum pump sealing oil, it reduces the oil’s ability to maintain a low micron seal as its vapor pressure rises, which in turn raises the vacuum level that can be achieved

How does the temperature of trapped water in a system change as a vacuum pump begins to remove the moisture? A. It increases significantly. B. It remains constant. C. It drops, causing more vapor volume per pound of water. D. It fluctuates unpredictably.

C. It drops, causing more vapor volume per pound of water. As the vacuum pump begins to remove the moisture, the water will boil and the temperature of the trapped water will drop, which then creates more vapor volume that must be removed per pound of water

How far from the vacuum pump should all micron gauges be located on the HVACR system for the most accurate reading? A. As close as possible to the vacuum pump. B. At the midpoint of the system. C. As far as possible from the vacuum pump. D. Connected directly to the vacuum pump's exhaust port.

C. As far as possible from the vacuum pump. All micron gauges should be located on the HVACR system as far as possible from the vacuum pump to ensure an accurate measurement of the vacuum in the system

How long should a standing pressure test typically be left on a 10-ton split system, if possible? A. 1 hour B. 4 hours C. Overnight, or for 24 hours D. 72 hours

C. Overnight, or for 24 hours. A larger system, such as a 10-ton split system, should be allowed to stand overnight, or for 24 hours, if possible

How long should an electronic leak detector test for an evaporator leak typically run, or until a leak is sensed? A. 1 minute B. 5 minutes C. 10 minutes D. 30 minutes

C. 10 minutes. Test with an electronic leak detector for a minimum of 10 minutes or until a leak is sensed

How many consecutive "positive" tests are needed to confirm an evaporator leak? A. One B. Two C. Three D. Four

B. Two. Two consecutive "positive" tests confirm an evaporator leak, while two consecutive "negative" tests rule it out

How many microns are in 1 inch of mercury (in. Hg)? A. 1,000 B. 2,036 C. 25,400 D. 51,715

C. 25,400. There are 25,400 microns in 1 inch

How many microns are in 1 millimeter of mercury (mm Hg)? A. 100 B. 1,000 C. 10,000 D. 25,400

B. 1,000. One thousand microns equal 1 mm Hg

If an evaporator section tests positive for a leak, what solution should be sprayed on all coil surfaces? A. Soap and water solution B. Household detergent C. Specially formulated bubble/foam promoter D. Plain water

C. Specially formulated bubble/foam promoter. If a leak is sensed, the technician should expose the coil and spray coat all surfaces with a specially formulated bubble/foam promoter

If the micron gauge reading continues to rise after the vacuum pump has been valved off, what could this indicate? A. The system is perfectly sealed. B. An atmospheric leak, boiling moisture, or refrigerant vapor seeping from the system. C. The vacuum pump oil is clean. D. The evacuation process is complete.

B. An atmospheric leak, boiling moisture, or refrigerant vapor seeping from the system. If the reading continues to rise, it indicates either an atmospheric leak or moisture is present and boiling to create pressure, or refrigerant vapor is still seeping

If the system pressure is reduced further during evacuation, and the water turns to ice, what is the process called when the ice then turns directly to a vapor without passing through the liquid state? A. Condensation B. Evaporation C. Sublimation D. Freezing

C. Sublimation. The process of a solid turning to vapor without passing through the liquid state is referred to as sublimation

In refrigeration systems, which specific metals are prone to electroplating from copper? A. Brass and aluminum. B. Copper to steel. C. Cast iron to brass. D. Steel to aluminum.

B. Copper to steel. Electroplating in refrigeration systems seems to only plate from copper to steel, specifically copper from the pipes onto the crankshaft and bearing surfaces

In the deep vacuum method, if the pressure rises after the pump is valved off and then stops at some point, what does this indicate? A. A large leak is present. B. The system is leak-free and dry. C. A material such as water is boiling in the system, or dissolved refrigerant is coming out of the oil. D. The vacuum pump is malfunctioning.

C. A material such as water is boiling in the system, or dissolved refrigerant is coming out of the oil. If the pressure rises and stops at some point, it indicates that a material such as water is boiling in the system, or dissolved refrigerant is still coming out of the oil in the compressor crankcase

In the HVACR industry, what is the combined process of removing both air and water vapor referred to as? A. Refrigerant recovery B. System purging C. Evacuation D. Degassing

C. Evacuation. In the HVACR industry, the process of removing both air and water vapor is referred to as evacuation

In what sequence should suspected surfaces be coated with microfoam solution when testing for pressure-dependent leaks? A. Evaporator, then condenser, then suction line. B. Discharge line, then suction line, then evaporator. C. Compressor and suction line, then discharge line to condenser, then liquid line, then evaporator. D. Liquid line, then compressor, then evaporator.

C. Compressor and suction line, then discharge line to condenser, then liquid line, then evaporator. The search typically starts with the compressor and suction line due to their large surface areas, then continues to the discharge line, across the condenser, to the liquid line connections, and finally to the evaporator section

To isolate a leak to either the indoor or outdoor unit in a split system, how can the low-pressure side of the system be isolated and pressurized? A. By completely evacuating the system and waiting. B. By disconnecting the liquid line and the suction line at the outdoor unit and pressurizing the entire low-pressure side. C. By adding a large amount of refrigerant to the system. D. By running the compressor at maximum capacity.

B. By disconnecting the liquid line and the suction line at the outdoor unit and pressurizing the entire low-pressure side. This will isolate the leak to the indoor or outdoor unit, allowing the indoor portion to be pressurized for testing

To prevent air from being trapped in one side of the system, how should a technician attach the vacuum pump when pulling a vacuum on a refrigeration system? A. To the high-pressure side only. B. To the low-pressure side only. C. To both the high- and the low-pressure sides of the system. D. To the evaporator section only.

C. To both the high- and the low-pressure sides of the system. The technician should attach the vacuum pump to the high- and the low-pressure sides of the system to prevent air from being trapped in one side

True or False: A system that has been operating and still contains refrigerant should generally be recovered and then pressured with nitrogen for a high-pressure leak test, even if it is time-consuming.

True. For an operating system with refrigerant, it is recommended that the refrigerant be properly recovered and the system pressured with nitrogen for a high-pressure leak test, as this will produce the best results despite being time-consuming

True or False: All sealed refrigeration systems are entirely leak-free upon installation.

False. All sealed systems leak to some degree, as flaws exist at every joint fitting, seam, or weld

True or False: Mixing vacuum pump oil with the cooling system's oil can cause serious damage to the cooling system.

True. Vacuum pump oil in the refrigeration or air-conditioning system can also damage the system because vacuum pump oil is designed for pumps only, and mixing it with the cooling system’s oil will do serious damage

True or False: Mixtures of nitrogen and a trace gas of refrigerant for leak testing are permissible, as long as the trace gas is a chlorofluorocarbon (CFC).

False. While mixtures of nitrogen and a trace gas are permissible, the use of a chlorofluorocarbon (CFC) as a trace gas is not permitted

True or False: Most residential systems, which often hold less than 10 lb of refrigerant, do not require leak repair according to EPA regulations.

True. Most residential systems hold less than 10 lb of refrigerant and do not require leak repair under EPA regulations

True or False: Using a vacuum for leak checking is a proper and recommended leak test procedure for refrigeration systems.

False. While a rising vacuum gauge might indicate a leak, this is not a recommended leak test procedure because it only tests for a reverse pressure of 14.696 psi, which is much less than system operating pressures, and it can hide leaks

What are cumulative microleaks? A. Leaks that can only be detected by a change in system temperature. B. Individual leaks too small to detect with standard tools, resulting in total refrigerant loss over many years. C. Leaks that appear only when the system is under vacuum. D. Leaks caused by the mechanical strain of motion.

B. Individual leaks too small to detect with standard tools, resulting in total refrigerant loss over many years. Cumulative microleaks are individual leaks that are too small to detect with standard tools, where the total refrigerant loss over many years slightly reduces the initial charge

What are the three common units of measurement for vacuum mentioned in the source? A. Pounds per square inch, cubic feet per minute, and degrees Fahrenheit. B. Millimeters of mercury, inches of mercury, and microns. C. Pascals, bars, and atmospheres. D. Gallons, liters, and ounces.

B. Millimeters of mercury, inches of mercury, and microns. Vacuum is commonly expressed in millimeters of mercury (mm Hg); it can also be expressed in inches of mercury and microns

What are the three elements required for electroplating to occur in a refrigeration system? A. Heat, pressure, and refrigerant. B. Electrical current, acid, and dissimilar metals. C. Oil, water, and oxygen. D. Nitrogen, hydrogen, and carbon.

B. Electrical current, acid, and dissimilar metals. Electroplating requires electrical current, acid, and dissimilar metals, and in refrigeration systems, copper from pipes can plate onto steel surfaces like crankshafts and bearings

What are the two primary problems caused by gases in the air when present in a refrigeration system? A. Increased cooling capacity and reduced energy consumption. B. Nitrogen acting as a noncondensable gas, and other gases causing chemical reactions that produce acids. C. Improved lubrication and extended system life. D. Higher boiling points for refrigerants and reduced pressure.

B. Nitrogen acting as a noncondensable gas, and other gases causing chemical reactions that produce acids. The nitrogen in the air is a noncondensable gas, and other gases cause chemical reactions that produce acids within the system

What can be an indication of very high refrigerant concentrations when using brazing torches, requiring immediate work stoppage and ventilation? A. A change in the sound of the flame. B. A visible change in the size or color of the flame. C. A sudden drop in system pressure. D. The presence of oil residue around the joint.

B. A visible change in the size or color of the flame. If you detect a visible change in the size or color of the flame when using brazing torches to repair equipment, stop work immediately and ventilate the area

What can be introduced into a system along with nitrogen to allow electronic leak detectors to detect the vicinity of a pressure-dependent leak? A. Microfoam solution B. A refrigerant trace gas C. Water D. Liquid nitrogen

B. A refrigerant trace gas. When necessary, a refrigerant trace gas can be introduced into the system along with the nitrogen to allow electronic leak detectors to find the vicinity of the leak

What can contaminate a vacuum pump's oil if it is stored in a truck, especially with weather changes? A. Road vibrations. B. Atmospheric moisture migrating into the pump. C. Engine exhaust fumes. D. Direct sunlight exposure.

B. Atmospheric moisture migrating into the pump. If stored in a truck, it is open to the atmosphere, and moisture from the atmosphere can enter the pump as it heats and cools, causing contamination

What can occur in the liquid line between the expansion valve and a normally closed solenoid valve if the solenoid valve is not opened during evacuation? A. The liquid line will be over-pressurized. B. Refrigerant will bypass the evaporator. C. Air may be trapped in that section. D. The expansion valve will malfunction.

C. Air may be trapped in that section. A system may have a normally closed solenoid valve which may trap air in the liquid line between the expansion valve and the solenoid valve, so it must be opened for complete evacuation

What can overexposure to high concentrations of refrigerant vapor cause? A. Minor skin irritation B. Asphyxiation and cardiac arrest C. Temporary vision impairment D. Increased energy levels

B. Asphyxiation and cardiac arrest. Overexposure to high concentrations of refrigerant vapor can cause asphyxiation and cardiac arrest

What can water potentially do to the oil in a vacuum pump's crankcase if the system is heavily laden with moisture during evacuation? A. Increase its viscosity. B. Cause it to turn blue. C. Displace the oil and push it out of the pump, potentially leading to damage if water becomes the only lubricant. D. Cause it to evaporate faster.

C. Displace the oil and push it out of the pump, potentially leading to damage if water becomes the only lubricant. Water can displace the oil and push it out of the pump, leading to a situation where water may be the only lubricant and damage may occur

What characteristic distinguishes dye-saturated oil from other leak detection methods, in terms of visual indication? A. It changes the color of the refrigerant. B. It causes a red dye residue to seep out wherever there is a leak and escaping oil. C. It produces a green glow under normal light. D. It forms large bubbles that pinpoint the leak.

B. It causes a red dye residue to seep out wherever there is a leak and escaping oil. Dye-saturated oil is a leak detection system that causes a red dye residue to seep out wherever there is a leak and escaping oil

What chemical reaction occurs between refrigerants (containing chlorine or fluorine) and water to form hydrochloric or hydrofluoric acids and more water? A. Oxidation B. Polymerization C. Hydrolysis D. Neutralization

C. Hydrolysis. Refrigerants such as R-12, R-502, R-22, R-134a, and newer blends containing chlorine or fluorine will hydrolyze (a chemical reaction) with water, forming hydrochloric or hydrofluoric acids and more water

What combination of substances forms acids and water from a portion of the refrigerant and oil mixture during a motor burnout? A. Air and moisture. B. High temperature arc, refrigerant, and oil. C. Nitrogen and carbon. D. Lubricant and metals.

B. High temperature arc, refrigerant, and oil. The high temperature arc of a motor burnout inside a compressor also causes a portion of the refrigerant and oil mixture to break down into carbonaceous sludge, corrosive acids, and water

What combination of substances in a system leads to the formation of acids after a short period of time? A. Nitrogen, oxygen, and oil. B. Moisture (water vapor), heat, and refrigerant. C. Sludge, copper, and steel. D. Lubricant, seals, and gaskets.

B. Moisture (water vapor), heat, and refrigerant. When moisture (water vapor), heat, and refrigerant are all present in a system, acids will start to form after a short period of time

What common problem can occur if a standard brass cap is screwed down too tightly on a Schrader valve port? A. It can cause the valve to stick open. B. It can create a false leak signal. C. It may crush the delicate seat in the valve, making the valve core impossible to remove. D. It can prevent refrigerant from flowing properly.

C. It may crush the delicate seat in the valve, making the valve core impossible to remove. If a brass cap is screwed down too tight, it may crush the delicate seat in the valve so far down that the valve core cannot ever be removed

What component in the ends of most gauge hoses restrict the evacuation process and slow down vacuum speed considerably? A. Schrader valve caps B. Valve stem depressors C. Hose crimps D. Quick-connect fittings

B. Valve stem depressors. Most gauge manifolds have valve stem depressors in the ends of the gauge hoses, which restrict the evacuation process and slow down vacuum speed considerably

What component of air causes oxidation on pipes when brazing if dry nitrogen is not used? A. Hydrogen B. Carbon dioxide C. Oxygen (20% content) D. Nitrogen

C. Oxygen (20% content). The 20% oxygen content of the air causes the oxidation on pipes when brazing if dry nitrogen is not used

What does it signify if the system pressure is reduced to 250 to 500 microns and remains constant? A. A hidden leak is present. B. No noncondensable gas or moisture is left in the system. C. The vacuum pump is too small. D. The system is overcharged.

B. No noncondensable gas or moisture is left in the system. When pressure is reduced to 250 to 500 microns and remains constant, it indicates that no noncondensable gas or moisture is left in the system

What feature allows some modern electronic leak detectors to work in refrigerant-contaminated areas? A. Manual recalibration B. Automatic recalibration C. Increased probe length D. Battery indicator

B. Automatic recalibration. The detector will automatically recalibrate for working in refrigerant-contaminated areas

What happens if a standard brass flare cap is overtightened on a Schrader valve top? A. It improves the seal. B. The Schrader valve top will be distorted, making valve stem service difficult or impossible. C. It will cause a vacuum leak. D. It will increase the system pressure.

B. The Schrader valve top will be distorted, making valve stem service difficult or impossible. If a standard brass flare cap is used and overtightened, the Schrader valve top will be distorted, making valve stem service difficult, if it can be done at all

What happens to a vacuum pump's oil sump after evacuating a contaminated system? A. It remains pristine and clean. B. It becomes contaminated with whatever was evacuated, including acids and moisture. C. It becomes a vacuum. D. It increases in volume.

B. It becomes contaminated with whatever was evacuated, including acids and moisture. All contaminants seem to settle in the oil sump of the vacuum pump, which can contain acids and moisture

What happens when nitrogen, a noncondensable gas, occupies condenser space in a refrigeration system? A. It condenses and enhances cooling. B. It increases the system's efficiency. C. It causes a rise in head pressure and a resulting increase in discharge temperatures and compression ratios, leading to inefficiencies. D. It acts as an inert buffer, protecting components.

C. It causes a rise in head pressure and a resulting increase in discharge temperatures and compression ratios, leading to inefficiencies. Nitrogen, as a noncondensable gas, will occupy condenser space that would normally be used for condensing refrigerants, causing a rise in head pressure and increased discharge temperatures and compression ratios

What is a "cold trap" used for in the field when evacuating systems with large amounts of moisture? A. To cool the vacuum pump motor. B. To condense refrigerant vapor for recovery. C. A refrigerated volume in the vacuum line where moisture freezes to its walls, preventing contamination of the vacuum pump. D. To chill the system before evacuation.

C. A refrigerated volume in the vacuum line between the wet system and the vacuum pump, where moisture freezes to the walls, typically refrigerated with dry ice

What is a "core removal tool" used for in relation to Schrader valves? A. To clean the valve. B. To replace Schrader valve stems under pressure or to act as a control valve during evacuation by backing out the stem. C. To tighten Schrader valve caps. D. To measure valve stem length.

B. To replace Schrader valve stems under pressure or to act as a control valve during evacuation by backing out the stem. The tool has a valve arrangement that allows evacuation through it with the stem backed out, and the stem is replaced when evacuation is completed

What is a "leak" defined as in the context of refrigeration systems? A. Any arbitrary reading on a meter B. A physical path or hole, usually of irregular dimensions C. The complete absence of pressure in a system D. A chemical reaction causing gas escape

B. A physical path or hole, usually of irregular dimensions. A leak is defined as a physical path or hole, often with irregular dimensions, which could be the end of a fracture, a speck of dirt on a gasket, or a microgroove between fittings

What is a common disadvantage of using a typical gauge manifold for system evacuation? A. They are too heavy. B. They have very small valve ports that slow the evacuation process. C. They are not compatible with modern refrigerants. D. They require constant calibration.

B. They have very small valve ports that slow the evacuation process. A typical gauge manifold may not be the best choice for evacuation because it has very small valve ports that slow the process

What is a key advantage of specially formulated bubble/microfoam solutions over soap and water for leak detection? A. They evaporate more quickly. B. They contain chlorides that clean the system. C. They have coagulants and wet adhesives that soap and water solutions lack. D. They are less costly to use.

C. They have coagulants and wet adhesives that soap and water solutions lack. Microfoam solutions are superior because they contain coagulants and wet adhesives that a soap and water solution does not, and household detergents often contain chlorides that will pit and corrode brass and iron

What is a key advantage of the modern method of system evacuation that involves evacuating without the use of a gauge manifold? A. It is less expensive. B. It reduces resistance to flow, increasing speed and producing deeper vacuum levels. C. It eliminates the need for a vacuum pump. D. It allows for simultaneous charging and evacuation.

B. It reduces resistance to flow, increasing speed and producing deeper vacuum levels. This method reduces the resistance to flow, which can increase the speed of the evacuation process and produce deeper vacuum levels when proper equipment is used

What is a key characteristic of most leak detection dyes regarding lubricants? A. They are universally compatible with all lubricants. B. They are lubricant-specific, meaning different types are used with mineral oil, alkylbenzene, and ester-type lubricants. C. They only work with synthetic lubricants. D. They do not interact with lubricants.

B. They are lubricant-specific, meaning different types are used with mineral oil, alkylbenzene, and ester-type lubricants. Most dyes are lubricant-specific, requiring different types for mineral oil, alkylbenzene, and ester-type lubricants

What is a potential liability of electronic leak detectors, especially in areas with a lot of refrigerant in the air? A. Their high cost. B. Their short battery life. C. They may have a hard time locating where to start unless they have a feature that corrects for background refrigerant. D. They are too heavy to be practical.

C. They may have a hard time locating where to start unless they have a feature that corrects for background refrigerant. When there is a lot of refrigerant in the air, electronic detectors may have a hard time locating where to start unless they have a feature that allows them to correct for background refrigerant

What is a safety requirement for a cold-trap container? A. It must be made of plastic. B. It must be able to withstand atmospheric pressure (14.696 psi) pushing in when in a deep vacuum. C. It must be transparent. D. It must be electrically grounded.

B. It must be able to withstand atmospheric pressure (14.696 psi) pushing in when in a deep vacuum. The cold-trap container must be able to withstand atmospheric pressure, 14.696 psi, pushing in, when in a deep vacuum; a light-duty container can collapse

What is a significant risk if a vacuum pump shuts off during the night due to a power failure while a system is under vacuum? A. The vacuum pump will overheat. B. Vacuum pump oil may be sucked into the refrigeration system due to the strong pressure difference. C. The system will immediately re-pressurize to atmospheric pressure. D. The refrigerant will condense in the vacuum pump.

B. Vacuum pump oil may be sucked into the refrigeration system due to the strong pressure difference. If the pump shuts off during the night due to a power failure, oil may be sucked into the refrigeration system because of the strong pressure difference

What is an advantage of a four-valve gauge manifold compared to a three-hose manifold during evacuation and charging? A. It is more compact. B. It allows for switching between vacuum and refrigerant lines without disconnecting and purging air from hoses. C. It has a built-in micron gauge. D. It prevents oil suckback.

B. It allows for switching between vacuum and refrigerant lines without disconnecting and purging air from hoses. The two extra valves on a four-valve manifold are used to control the refrigerant and vacuum pump lines, making it easier and cleaner to change between them without drawing air into the hose

What is an important consideration before using a leak detection dye, especially if the system is under warranty? A. Whether it is compatible with all refrigerants. B. Consulting with the compressor manufacturer to ensure the dye is approved. C. The ambient temperature of the system. D. The size of the system's charge.

B. Consulting with the compressor manufacturer to ensure the dye is approved. Before performing this test, consult with the compressor manufacturer to ensure the dye is approved, particularly while the system is under warranty

What is considered the most common type of leak among all classes? A. Combination-dependent leaks B. Cumulative microleaks C. Pressure-dependent leaks D. Standing leaks

D. Standing leaks. Fortunately, standing leaks are the most common of all leaks

What is the approximate low vacuum level reached during the initial stages of a multiple evacuation before breaking the vacuum with nitrogen? A. 250 microns B. 500 microns C. 1500 microns D. 5000 microns

C. 1500 microns. The process involves evacuating a system to a low vacuum, about 1500 microns, before bleeding in dry nitrogen

What is the atmospheric pressure at sea level, in pounds per square inch absolute (psia) and inches of mercury (in. Hg)? A. 0 psia (0 in. Hg) B. 14.696 psia (29.92 in. Hg) C. 29.92 psia (14.696 in. Hg) D. 760 psia (760 in. Hg)

B. 14.696 psia (29.92 in. Hg). The atmosphere exerts a pressure of 14.696 psia (29.92 in. Hg) at sea level

What is the benefit of sweeping dry nitrogen through refrigerant lines during field installation, especially while soldering or brazing? A. It speeds up the brazing process. B. It prevents oxidation on the inside and outside of the brazed joints and keeps the atmosphere pushed out. C. It adds a protective coating to the pipes. D. It reduces the need for evacuation later.

B. It prevents oxidation on the inside and outside of the brazed joints and keeps the atmosphere pushed out. Slowly sweeping dry nitrogen through pipes during soldering or brazing will prevent oxidation, and it can also shorten evacuation time if the system has been open to the atmosphere

What is the CFM (cubic feet per minute) rating at which a vacuum pump can pull when connected to a 1/4 inch service hose, regardless of the pump's actual CFM rating? A. 0.8 CFM B. 1.5 CFM C. 2.0 CFM D. The pump's full capacity

A. 0.8 CFM. A 1/4 inch service hose will only allow a vacuum pump to pull at 0.8 CFM, regardless of the vacuum pump’s CFM rating

What is the consequence of the breakdown of electric motor insulation caused by acids in a refrigeration system? A. Improved motor performance. B. Reduced motor noise. C. Electrical short circuits, causing ground or phase-to-phase shorts. D. Increased motor lifespan.

C. Electrical short circuits, causing ground or phase-to-phase shorts. The equally serious problem of the breakdown of electric motor insulation will cause electrical short circuits and either ground or short the motor from phase to phase

What is the final deep vacuum level required for a triple evacuation, and how long should it be held? A. 1500 microns for 5 minutes. B. 250 to 500 microns for 10 to 15 minutes. C. 100 microns for 30 minutes. D. 0 microns for an hour.

B. 250 to 500 microns for 10 to 15 minutes. The final vacuum level should be from 250 to 500 microns and held for 10 to 15 minutes

What is the first step when testing for evaporator section leaks using an electronic screening method? A. Add a refrigerant trace gas. B. Calibrate an electronic leak detector. C. Turn off all system power. D. Position the electronic leak detector probe at the drain opening.

C. Turn off all system power. The first step is to turn off all system power, including evaporator fan motors

What is the lowest sensitivity level mentioned for a modern infrared sensor-equipped electronic leak detector? A. 0.5 oz/year B. 0.25 oz/year C. 0.1 oz/year D. 0.05 oz/year

C. 0.1 oz/year. This type of leak detector features three sensitivity levels, down to 0.1 oz/year

What is the main reason two-stage vacuum pumps can pull much lower vacuums compared to single-stage pumps? A. They have a larger oil reservoir. B. Their second stage experiences a much lower intake pressure because it receives the exhaust from the first stage. C. They operate at a higher RPM. D. They use a different type of vacuum pump oil.

B. Their second stage experiences a much lower intake pressure because it receives the exhaust from the first stage. Two-stage vacuum pumps can pull much lower vacuums because their second stage experiences a much lower intake pressure, which is the result of the exhaust of the first-stage pump being exhausted into its intake

What is the minimum monitoring time for leakage when testing a condensing unit, or until a leak is sensed? A. 5 minutes B. 10 minutes C. 15 minutes D. 20 minutes

B. 10 minutes. Monitor for leakage for 10 minutes or until a leak is sensed

What is the most basic but effective method of detecting leaks, which might not pinpoint the exact location but helps narrow down the area? A. Using an electronic leak detector. B. Applying a microfoam solution. C. Just listening for the rush of nitrogen from the connections. D. Using an ultraviolet dye kit.

C. Just listening for the rush of nitrogen from the connections. The most basic but effective method is to just listen for the rush of nitrogen from the connections, as often leaks can be heard but not pinpointed

What is the most frequently used method of leak detection, often employed for newly assembled systems? A. The bubble test B. The standing pressure test C. The electronic sniff test D. The oil spotting method

B. The standing pressure test. The standing pressure test is probably the most frequently used method of leak detection, often for newly assembled systems

What is the normal procedure for a multiple or triple evacuation? A. Evacuate to deep vacuum, then add refrigerant, then re-evacuate. B. Evacuate to a low vacuum (e.g., 1500 microns), bleed dry nitrogen, re-evacuate, repeating this procedure three times, with the last vacuum reaching 250-500 microns. C. Evacuate, then apply heat, then re-evacuate. D. Evacuate only the high side, then the low side, then the entire system.

B. Evacuate to a low vacuum (e.g., 1500 microns), bleed dry nitrogen, re-evacuate, repeating this procedure three times, with the last vacuum reaching 250-500 microns. This procedure is normally accomplished by evacuating to a low vacuum, about 1500 microns, then bleeding a small amount of dry nitrogen into the system, repeating three times, with the final vacuum held at 250 to 500 microns for 10 to 15 minutes

What is the only sure way to rid a cooling system of moisture to avoid corrosion and sludge problems? A. Flushing with refrigerant. B. Replacing all system components. C. Through effective evacuation procedures using a high-capacity vacuum pump. D. Adding anti-moisture additives to the oil.

C. Through effective evacuation procedures using a high-capacity vacuum pump. The only sure way to rid the cooling system of moisture is through effective evacuation procedures using a high-capacity vacuum pump

What is the only true indicator of when vacuum pump oil needs to be changed for optimal performance? A. The amount of time the pump has been running. B. The volume of refrigerant recovered. C. The micron gauge reading. D. The pump's physical temperature.

C. The micron gauge reading. The micron gauge is the only true indicator as to when the oil needs to be changed, as a slower pumping rate and inability to reach deep vacuums indicate contaminated oil

What is the primary difference between a refrigeration system and a bell jar when discussing vacuum, as described in the source? A. A refrigeration system is airtight, while a bell jar is not. B. A refrigeration system is composed of many small chambers connected by piping. C. A bell jar contains a liquid, while a refrigeration system contains gas. D. A refrigeration system has a constant internal pressure.

B. A refrigeration system is composed of many small chambers connected by piping. Unlike a simple bell jar, a refrigeration system is composed of many small chambers connected by piping, including compressor cylinders

What is the primary visual indicator that vacuum pump oil needs to be changed? A. It becomes clear and thin. B. It changes color to bright blue. C. It is cloudy, indicating moisture. D. It increases in viscosity.

C. It is cloudy, indicating moisture. The oil in the vacuum pump must be changed regularly for good pump performance; if it is cloudy, moisture is likely present

What is the process of removing air and/or other noncondensable gases from a system with a vacuum pump called? A. Dehydration B. Degassing C. Evacuation D. Purification

B. Degassing. Removing air and/or other noncondensable gases from a system with a vacuum pump is called degassing a system

What is the process of removing water vapor from a system known as? A. Degassing B. Dehumidification C. Dehydration D. Desiccation

C. Dehydration. Removing water vapor from a system is known as dehydration

What is the purpose of the ball valves equipped on core removal tools in manifold-less evacuation? A. To control refrigerant flow. B. To isolate the system from the pump to perform a time-to-rise test. C. To release excess pressure. D. To connect multiple vacuum pumps.

B. To isolate the system from the pump to perform a time-to-rise test. The core removal tools are equipped with ball valves that are used to isolate the system from the pump to perform a time-to-rise test, which evaluates the rise in system pressure with respect to time

What is the role of vacuum pump oil as a "liquid seal" in two-stage rotary vacuum pumps? A. It lubricates the motor only. B. It cools the pump exterior. C. It acts as a liquid seal between the vanes and the cylinder walls. D. It filters contaminants from the system.

C. It acts as a liquid seal between the vanes and the cylinder walls. The vacuum pump oil is a liquid seal between the vanes and the cylinder walls of all two-stage rotary vacuum pumps

What is the source of heat in a hermetic motor burnout that breaks down refrigerant and oil into acids, soot, and sludge? A. External flames. B. The heat generated by the motor burnout itself. C. High ambient temperatures. D. Chemical reactions with water.

B. The heat generated by the motor burnout itself. The hermetic motor inside a sealed system is the source of heat in a motor burnout, which can raise the refrigerant and oil to temperatures that will break them down