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MIDTERM UNITS 1-8 > UNIT 8 > Flashcards

UNIT 8 Flashcards

1
Q

Vacuum below 25 in HG

A

Deep vacuum

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2
Q

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

A

Nitrogen

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3
Q

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

A

Noncondensible gas

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4
Q

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.

A

Schrader valve

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5
Q

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

A

Vacuum

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6
Q

Oxygen nitrogen, water vapor, and other noncondensible gases

A

Contaminants

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7
Q

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

A

Micron

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8
Q

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

A

Vacuum pump

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9
Q

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

A

Refrigerant recovery

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10
Q

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.

A

Cold trap

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11
Q

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

A

Terminal venting

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12
Q

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

A

To obtain a more accurate reading

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13
Q

How is acid formed in a system?

A

Heat + refrigerant + moisture= acid

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14
Q

How does moisture get into a system?

A

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

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15
Q

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.

A

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.

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16
Q

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

A

25 tons

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17
Q

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

A

HH

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18
Q

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

A

False

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19
Q

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

A

True

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20
Q

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

A

False

21
Q

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

A

False

22
Q

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

A

True

23
Q

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

A

True

24
Q

True or false
Defrost an evaporator before performing a leak check

A

True

25
Q

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

A

False

26
Q

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

A

False

27
Q

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

A

False

28
Q

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

A

True

29
Q

To raise the operating temperature of the system, block the___________

A

Condenser

30
Q

When testing a system for combination leaks,___________

A

All of the above

31
Q

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

A

Back seated

32
Q

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

A

Front seat

33
Q

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

A

Vibration, dependent leaks

34
Q

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?

A

Plastic sheet/tarp

35
Q

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

A

9 CFM two stage

36
Q

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

A

12 CFM two stage

37
Q

What does the check valve in a vacuum pump prevent?

A

Vacuum pump oil from flowing into the system being evacuated

38
Q

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

A

Soft copper tubing

39
Q

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

A

4 and 4

40
Q

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

A

All bearing surfaces

41
Q

What would you use to open a solenoid valve?

A

A magnet

42
Q

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

A

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

43
Q

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

A

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

44
Q

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

A

Mid seat

45
Q

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?

A

Charge the system with nitrogen or refrigerant

46
Q

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

A

12 ohm contactor

47
Q

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

A

1.6A

48
Q

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

A

5/8” copper tubing

MIDTERM UNITS 1-8 (8 decks)

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