Chows Unit 8

Question 1

True or false 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.

Answer 1

False

Question 2

Air entering a refrigerant system can eventually lead to compressor failure

Answer 2

True

Question 3

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

Answer 3

True

Question 4

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 effects on the system

Answer 4

False

Question 5

True or false clearance tolerances are such that the ordinary, clean refrigerant oil can be used satisfactorily in a vacuum pump

Answer 5

False

Question 6

True or false The oil in a vacuum pump should be changed after each time it is used

Answer 6

True

Question 7

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

Answer 7

Oxygen

Question 8

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

Answer 8

Refrigerant

Question 9

____________ microns is equal to 1 mm Hg.

Answer 9

1000

Question 10

The electronic vacuum gauge is attached to the system so it can measure the pressure ________ the system

Answer 10

Inside

Question 11

A vacuum involves reducing the pressure in a refrigeration system to a micron gauge reading of _______ or below

Answer 11

300

Question 12

There are _________ microns in 1 mm Hg.

Answer 12

1000

Question 13

Sludge is produced when moisture acid and _________ are present in the system

Answer 13

Oil

Question 14

A __________ pressure could also mean refrigerant vapor is still seeping from the refrigeration system.

Answer 14

Rise in

Question 15

Explain why, triple evacuations are not normally performed on large systems.

Answer 15

It takes too much time and it would take a lot of nitrogen to pressurize a large system correctly.

Question 16

A pressure of 100 µm has been reached with the vacuum pump operating. The pump is turned off and the gauge reading rises to 5000 microns and stays there. What does this indicate?

Answer 16

This indicates that there is still moisture within the system that still needs to boil off

Question 17

A pressure of 100 µm has been reached with the vacuum pump operating. The pump is turned off and the gauge reading rises to 500 µm and stays there. What does this indicate?

Answer 17

500 µm would indicate that the system has little to no moisture and that no leaks are present. This is an acceptable number of microns as long as it holds for 10 minutes.

Question 18

Why is refrigerant not used for a system standing pressure test?

Answer 18

Because the pressure/temperature relationship with refrigerant vary, the pressure readings will not be accurate. If the leak is big, the refrigerant will be released into the atmosphere against EPA rules. Using nitrogen is cheaper and OK to be released into the atmosphere.

Question 19

Why is nitrogen considered a noncondensible gas?

Answer 19

Unlike refrigerant, nitrogen cannot change states

Question 20

A pressure of 100 µm has been reached with the vacuum pump operating. The pump is turned off in the gauge reading rides is above 5000 µm and keeps rising. What does this indicate?

Answer 20

More than likely, there is still a leak within the system, and at this point, the system is sucking in atmospheric pressure

Question 21

Why must all valves be opened when an evacuation is performed?

Answer 21

All valves should be opened to ensure that the entire system is being dehydrated/degassed

Question 22

Why is it a good idea to remove schrader stems from service valve ports prior to evacuation?

Answer 22

Schrader stems restrict flow by 90%. This makes pulling a deep vacuum, more time-consuming then it has to be.

Question 23

A micron gauge is used to measure…….

Answer 23

Absolute pressure below 1 mm Hg.

Question 24

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

Answer 24

Copper tubing

Question 25

The best method of leak checking is when the refrigeration system is…………

Answer 25

Standing with dry nitrogen pressure of 150 psig in the system

Question 26

A multiple evacuation means that……..

Answer 26

You pull a vacuum on a refrigeration system more than once, allowing refrigerant or nitrogen into the system between each procedure

Question 27

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

Answer 27

Acid

Question 28

Noncondensible gases……

Answer 28

Are undesirable in a refrigeration system

Question 29

Which of the following represents the lowest vacuum?

Answer 29

1000 µm

Question 30

A compound gauge……….

Answer 30

Indicates pressures in inches Hg below atmospheric pressure Is one of two cages on a typical gauge manifold Indicates pressures above 14.696 Psia

Question 31

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

Answer 31

500 to 300 microns

Question 32

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

Answer 32

Vaporized

Question 33

To pull a vacuum means to________

Answer 33

Lower the pressure in a refrigeration system below atmospheric pressure

Question 34

Name 6

Question 35

True or false bishop says when performing a triple evacuation, the best place to locate the electronic micron gauge is as far away from the vacuum port as possible.

Answer 35

True

Question 36

True or false when using a pressure gauge for standing leak test, tapping the gauge with a 16oz hammer is a good way to make sure the needle is free.

Answer 36

False

Question 37

What is the importance of installing a site glass in a system? And where should you locate it?

Answer 37

A site class can be utilized to ensure the refrigerant is in its proper state, depending on the area of the system it is installed on. Good place to install this site glass would be in between the condenser filter, dryer and metering device or in between the condenser and evaporator to see the refrigerant is ex experiencing a face change and flashing off.

Question 38

How can we use our senses when searching for a refrigerant leak on a refrigeration system or AC system, without the use of tools? Name all of them and explain.

Answer 38

Smell- refrigerant has a unique odor and smells different compared to system oil. Sight- visual inspection, if there is oil residue on the ground near tubing, there may be a leak in that area Sound- listen for a hissing sound, that’s a good indication of a leak Feel- suction line should be beer can cold

Question 39

List tools we as techs use to search for leaks on an air conditioning and refrigeration system? List all you can think of.

Answer 39

Halide leak detector Ultraviolet leak detector Ultrasonic leak detector Electronic leak detector Nitrogen Tarps or sheets to cover condenser for a more accurate reading Micro foam solution Soap bubble solution (Electronic first, soap 2nd, ultrasonic 3rd, UV last)

Question 40

Daniel and kamyl are pulling vacuum on a Mitsubishi city mill system and need to get down to 500 microns quickly so they can go eat lunch. What are some ways they can increase productivity of the dehydration and evacuation process?

Answer 40

Utilize 1/2 “ hoses Use more than one vacuum pump Make sure service port stems are removed before vacuuming Run vacuum through lunchbreak Send one person to go pick up lunch

Question 41

T/f we are condensable and moisture are left in the system hydrochloric and hydroscopic acids will form and deteriorate the motor windings and cause copper plating.

Answer 41

False

Question 42

List some ways to clean out contaminates from motor burnout on a semi hermetic compressor.

Answer 42

Drain and replace oil after performing a triple evacuation Install “HH” filter drier to catch as much acid/ non condensibles as possible

Question 43

Christian responds to a service call, the store managers complaint is that the walk in chill box is warm. The board of health was just there that morning and gave them a yellow card………..Sean climbs on the roof and comes across a R22 unit and finds a suction line filter drier on condensing unit. The drier frosted up and then defrost………what could be wrong with the system?

Answer 43

Potential restriction in the filter drier I would change the filter with a brand new one. I would also place insulation around the suction line to prevent unnecessary heat being added into the system and to prevent condensation. Check data plate for testing and standard operational pressures. Make sure metering device is functioning correctly and also check evap coil to make sure it is not “icing”

Question 44

How would you replace the oil in module. Give me step by step

Answer 44

Access the service port on the compressor that is utilized for adding and removing oil. For deep cleaning, open compressor with ratcheting/socket set and wipe inside of compressor with approved cleaning equipment. Run a deep vacuum before placing new oil in compressor Check with manufacturer for correct amount of oil to be placed in compressor. If its a quick and dirty, check the sight glass before taking the oil out and place back in the same amount taken out

Question 45

Jonas and mark are on a job at uh manoa biochem lab and the mechanical inspector for the job site asked them a question while they are pulling vacuum on a VRF system during an install. They can’t get the Mirons down past 1000. What should they do?……

Answer 45

If my levels reached 30,000 there is still a leak present somewhere. I would inform the inspector that the system still has a leak and no, I cannot just pass them because my license is on the line. Since there is no refrigerant in the system, I would pressurize the system with nitrogen and tracer gas. I would then utilize an electronic leak detector to search for the leak. If I can’t find it, I would do a 24 hour standing pressure test and revisit.

Question 46

Larger hoses increase pumping capacity of a 5 CFM pump with 3/8 in. Hoses by ______ vs. a 1/4 in. Hose?

Answer 46

4X

Question 47

What happens when air gets trapped in a refrigeration system?

Answer 47

Air contains moisture that can create acid when mixed with refrigerant and heat. Acid creates high head pressures that causes copper plating on crankshafts and bearings. Can also cause slow burn out of compressor. This can also take up space in the condenser making it more difficult for refrigerant to condense

Question 48

What can you do if you can’t find a leak on a split system in a business where the condenser is on the roof and the evaporator is 3 floors down?

Answer 48

Isolate the indoor and outdoor units to make it easier to find leak. Start by checking the condenser on the roof (bring a tarp to cover the condenser). If utilizing dye, inject the dye into the system and come back in the evening to confirm leak if still not able to find with electronic.

Question 49

Lee jay is dispatched to check for a leak on a condensing unit at the top of the mountain of Peacock flats. What should he think of taking and how should he proceed to find the leak if it’s windy out that day?

Answer 49

Bring a tarp to cover the condenser unit. Fridge is heavier than air so eliminating draft air can help with finding a positive leak . Take your time and check the entire coil . There may be more than one leak present. Electronic leak detector Soap bubble Rags

Question 50

Name 6 different types of leaks

Answer 50

Standing, pressure, temperature, combo, vibration, accumullative (MICROLEAKS)

Question 51

Leaks can flow under…..

Answer 51

Paint, flux, rust, pipe insulation

Question 52

We need to wash down leaks after checking with soap or it will….

Answer 52

Corrode, oxidize, rust

Question 53

How many microns in an inch?

Answer 53

25,400

Question 54

How would you remove sludge from your system?

Answer 54

Install HH suction dryer and wait 48 hours before removing

Question 55

If electroplating has happened in your system what would you find if you were to open up your system? What should you check?

Answer 55

You could find acid or sludge. Check to see if your crankshaft and or bearings are OK and didn’t lock up . Compressor could be damaged. Check heat temp.

Question 56

1 pound of water equals to a…….. in a system and will turn into………..ft3 of vapor boiled at 70°F

Answer 56

1 pint / 867 ft3

Question 57

What does 305-S-HH mean?

Answer 57

30- cubic inches 5- 5/8 tube size S- Soldered on connection

Question 58

What would happen if you start a hermetic compressor that is in a deep vacuum? What is the outcome?

Answer 58

That would potentially cause “arcing” inside the compressor that would turn that compressor into a bomb.

Question 59

How could you test refrigerant to see if there is acid in a system or a tank of recovered refrigerant describe the method and types of products you can use and how to use them

Answer 59

Utilize an acid test kit that has two bottles put oil sample in one and add the other bottle. If it turns purple, it is contaminated.

Question 60

Describe the inside of a filter dryer and how it works draw it out

Answer 60

Inside a filter drier contains filters and charcoal aswell as a spring to filter and catch any moisture or acid if using an HH drier.