Question 1

Moisture in a liquid state must be ____ before it can be removed with a vacuum pump.

Accepted Answer

Moisture in a liquid state needs to be vaporized or turned into a gas in order to be removed with a vacuum pump. This is because vacuum pumps are designed to remove gases, not liquids.

Question 2

When using a "standing pressure test" for leak-checking, ____________________ should never be used since an explosive mixture can be created.

Accepted Answer

air

Question 3

The oil in a vacuum pump should be changed after each time it is used.

Accepted Answer

The oil in a vacuum pump should be changed after each time it is used to prevent contamination and ensure optimal performance.

Question 4

Noncondensable gases ____.

Accepted Answer

Noncondensable gases, such as air and nitrogen, can accumulate in a refrigeration system and reduce its efficiency. They are therefore undesirable and need to be removed. They do not condense readily under normal atmospheric conditions and do not help in pulling a vacuum.

Question 5

Only two substances should be in the refrigeration system for proper operation. They are ____________________ and oil.

Accepted Answer

The answer of Only two substances should be in the...

Question 6

A compound gauge ____.

Accepted Answer

A compound gauge indicates pressures above 14.696 psia as well as pressures in inches Hg below atmospheric pressure. It is one of two gauges on a typical gauge manifold.

Question 7

Air entering a refrigerant system can eventually lead to compressor failure.

Accepted Answer

Air in a refrigerant system can lead to the formation of moisture, which can combine with the refrigerant to form acids that can damage the compressor. Additionally, air can reduce the efficiency of the system and cause it to work harder than necessary, leading to premature failure.

Question 8

At what pressure range does the technician valve off the vacuum pump when evacuating to a deep vacuum?

Accepted Answer

The answer of At what pressure range does the technician...

Question 9

Clearance tolerances are such that the ordinary clean refrigerant oil can be used satisfactorily in a vacuum pump.

Accepted Answer

Vacuum pumps typically require specialized oils designed for high vacuum conditions, as ordinary refrigerant oils may not provide the necessary lubrication and may degrade under the low pressure conditions inside a vacuum pump.

Question 10

A micron gauge is used to measure ____.

Accepted Answer

A micron gauge is specifically designed to measure vacuum pressures, which are absolute pressures below 1 mm Hg (mercury). This tool is essential in applications like refrigeration and air conditioning systems maintenance, where achieving and verifying a deep vacuum is crucial.

Question 11

The best method of leak checking is when the refrigeration system is ____.

Accepted Answer

The best method for leak checking a refrigeration system is when it is standing with dry nitrogen pressure of 150 psig in the system. This method allows for the detection of leaks without moisture entering the system, which can cause damage or inaccurate readings.

Question 12

To pull a vacuum means to ____.

Accepted Answer

To pull a vacuum means to lower the pressure in a refrigeration system below atmospheric. This is typically done to remove any moisture or air from the system before charging it with refrigerant.

Question 13

Which of the following represents the lowest vacuum?

Accepted Answer

1000 microns represents a lower vacuum level compared to the other options. Vacuum levels are often measured in microns, where lower numbers indicate a higher vacuum. In contrast, psia (pounds per square inch absolute) and psig (pounds per square inch gauge) are pressure measurements, and inches of mercury (in. Hg) vacuum is less direct for comparing vacuum levels without conversion to an absolute scale like microns.

Question 14

When moisture is present in a refrigeration system, it will react with the refrigerant and the oil to form ____.

Accepted Answer

When moisture is present in a refrigeration system, it will react with the refrigerant and the oil to form acid. This can lead to corrosion, clogging of filters, and other issues that can damage the system. It is important to properly evacuate and dry the system before charging it with refrigerant to prevent moisture from entering the system.

Question 15

Sludge is produced when moisture, acid, and ____________________ are present in the system.

Accepted Answer

The answer of Sludge is produced when moisture, acid, and...

Question 16

The maximum recommended pressure for leak testing is 150 psig on the low-pressure side of the system.

Accepted Answer

The maximum recommended pressure for leak testing is generally 150 psig on the low-pressure side of the system. This is to ensure that the system is not damaged by excessive pressure during testing. However, the specific maximum pressure may vary depending on the type of system being tested and other factors, so it is important to follow the manufacturer's guidelines and any applicable regulations.

Question 17

To insure accurate testing, the best material to use for connecting lines to the vacuum pump and gauge set is ____.

Accepted Answer

Copper tube is the best material to use for connecting lines to the vacuum pump and gauge set as it provides a secure and leak-free connection, and is not affected by the vacuum pressure. Light flexible hose and garden hose are not recommended as they can collapse under high vacuum pressure and contaminate the system. Heavy duty rubber gauge line is a suitable alternative, but may not provide as secure a connection as copper tubing.

Question 18

While under a deep vacuum, any liquid water under the oil in the motor-compressor assembly can be removed by operating the compressor motor for several seconds without any adverse effect on the system.

Accepted Answer

Operating the compressor motor under these conditions can cause the liquid water to rapidly boil and expand, potentially causing mechanical damage to the system or creating moisture-related issues within the compressor or the system it serves.

Question 19

A multiple evacuation means that ____.

Accepted Answer

Multiple evacuation means that you pull a vacuum on a refrigeration system more than once, allowing refrigerant or nitrogen into the system between each procedure. This is done to ensure that all moisture and air is removed from the system, which is essential for proper functioning. It is important to note that multiple evacuation is different from connecting multiple vacuum pumps simultaneously to a refrigeration system (option A). Option B and D are not accurate descriptions of multiple evacuation.

Question 20

After repairing a system that has had an electrical motor failure (compressor burnout), it is good field practice to re-use the recovered refrigerant in that system.

Accepted Answer

It is not recommended to reintroduce recovered refrigerant into a system after a compressor burnout as the refrigerant may have become contaminated with acid or other debris during the burnout process, which could damage other components in the system. It is important to properly dispose of the recovered refrigerant and use fresh, uncontaminated refrigerant in the system.

Quiz 8: Leak Detection, System Evacuation and System Clean-Up