UNIT 8

Question 1

Vacuum below 25 in HG

Answer 1

Deep vacuum

Question 2

Inert Gas used to pressurize AC systems to leak check, remove contaminants and prevent oxidation while soldering

Answer 2

Nitrogen

Question 3

Gases that do not change to a liquid when it’s temperature is reduced

Answer 3

Noncondensible gas

Question 4

Much like the valve stem on an automobile and bicycle tires. Slows the vacuum process and should be removed during evacuation to speed up the process.

Answer 4

Schrader valve

Question 5

To lower the pressure in a system below the pressure of the atmosphere

Answer 5

Vacuum

Question 6

Oxygen nitrogen, water vapor, and other noncondensible gases

Answer 6

Contaminants

Question 7

The last inch of vacuum is measured in this unit of measure

Answer 7

Micron

Question 8

Reduces atmospheric pressure in a system. Can be single or two stage.

Answer 8

Vacuum pump

Question 9

To remove refrigerant from the system and store it in an external container, without necessarily testing or processing it in any way

Answer 9

Refrigerant recovery

Question 10

Used on large systems. Place between the wet system and vacuum pump. Water vapor passes through the container and hits the side of the walls and freezes saving the vacuum pump oil from being contaminated.

Answer 10

Cold trap

Question 11

Why should you never start a hermetic compressor when it is in a deep vacuum?

Answer 11

Terminal venting

Question 12

Why is the micron gauge placed as far away from the vacuum pump?

Answer 12

To obtain a more accurate reading

Question 13

How is acid formed in a system?

Answer 13

Heat + refrigerant + moisture= acid

Question 14

How does moisture get into a system?

Answer 14

Anytime the system is open, oxygen can easily travel into the system. Oxygen contains elements of moisture.

Question 15

A micron gauge reads 180 microns. The vacuum pump is valve off and the micron gauge starts to climb. It finally stops at 1500 microns. Is there a leak in the system? explain why the reading increased and stopped rising.

Answer 15

The reason why the reading increased is due to residual trapped underneath the oil such as refrigerant and water. Therefore, it’s not a leak.

Question 16

A 5CFM vacuum pump can be used on systems up to how many tons?

Answer 16

25 tons

Question 17

What is the two letter designation on a filter dryer that indicates the filter is used to remove acid from the system?

Answer 17

HH

Question 18

True or false
A vacuum pump can remove sludge from the system ?

Answer 18

False

Question 19

True or false
When under a deep vacuum, any trapped water or refrigerant underneath the oil in the compressor can be removed by heating and or beating on the compressor

Answer 19

True

Question 20

True or false
The oil in the vacuum pump should be changed after each use

Answer 20

False

Question 21

True or false
Clean refrigerant oil may be used in a vacuum pump

Answer 21

False

Question 22

True or false
The gas ballast feature on a vacuum pump, reduces the vapor from condensing inside the vacuum pump oil, thereby extending the life of the oil

Answer 22

True

Question 23

True or false
Acid in a system can break down motor insulation and cause a short circuit or ground to happen

Answer 23

True

Question 24

True or false
Defrost an evaporator before performing a leak check

Answer 24

True

Question 25

True or false The best way to perform a leak test is to pull the system into a vacuum

Answer 25

False

Question 26

True or false Oil present at a schrader or access port is a positive sign of a leak

Answer 26

False

Question 27

True or false The valves on the gauge manifold need to be open to read the system pressure when the service valves are opened

Answer 27

False

Question 28

True or false On systems where the high and low side cannot be isolated from each other, pressurize the system to the lowest pressure listed on the data plate

Answer 28

True

Question 29

To raise the operating temperature of the system, block the___________

Answer 29

Condenser

Question 30

When testing a system for combination leaks,___________

Answer 30

All of the above

Question 31

The suction and discharge valves in a system are positioned in the__________ position for normal operation

Answer 31

Back seated

Question 32

To stop the flow of refrigerant, flowing into the suction service port from the yellow hose,__________ the low side valve

Answer 32

Front seat

Question 33

Of the six types of leaks, which one is the rarest or least likely to happen?

Answer 33

Vibration, dependent leaks

Question 34

When isolating the condenser from outside air currents and to trap refrigerant gas to perform a leak check, what should not be used to prevent false positive readings from occurring?

Answer 34

Plastic sheet/tarp

Question 35

Which of the following vacuum pumps will produce the lowest vacuum?

Answer 35

9 CFM two stage

Question 36

The appropriate vacuum pump to use on a 144 ton system is a_______ vacuum pump

Answer 36

12 CFM two stage

Question 37

What does the check valve in a vacuum pump prevent?

Answer 37

Vacuum pump oil from flowing into the system being evacuated

Question 38

The best type of hose to use for finding a leak while pulling a vacuum is/are_______

Answer 38

Soft copper tubing

Question 39

The best manifold to use when evacuating and charging a system without having to disconnect hoses would be the______valve,______hose manifold

Answer 39

4 and 4

Question 40

If you suspect electroplating has occurred in a compressor, what parts should you check?

Answer 40

All bearing surfaces

Question 41

What would you use to open a solenoid valve?

Answer 41

A magnet

Question 42

What are two indicators that your vacuum pump oil needs to be changed?

Answer 42

visual inspection shows oil as cloudy micron gauge reading, shows numbers above 50 microns

Question 43

The four things you can do to speed up the evacuation of the system

Answer 43

Use larger, diameter hoses Use a two stage vacuum pump with highest CFM Evacuate without manifold Open all valves

Question 44

When recovering evacuating and charging refrigerant, what position should all service valves be placed in?

Answer 44

Mid seat

Question 45

Your system passed the decay test and stayed under 500 microns for a minimum of 10 minutes. You can’t leave the system in a vacuum. What do you do?

Answer 45

Charge the system with nitrogen or refrigerant

Question 46

Which contactor will not blow the 5A fuse on the low voltage side of the system if the transformer puts out 27VAC?

Answer 46

12 ohm contactor

Question 47

A transformer puts out 24VAC. It is rated for 40VA. What is the maximum current flow on the output side of this transformer?

Answer 47

1.6A

Question 48

1/2 “ ACR copper tubing is equivalent to what size nominal copper tubing?

Answer 48

5/8” copper tubing