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AC Refrigeration > AC > Flashcards

AC Flashcards

1
Q

The pressure at which the refrigerant changes state from a vapor to liquid

A

Condensing pressure

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2
Q

The pressure at which the refrigerant changes state from a liquid to vapor

A

Evaporating pressure

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3
Q

T/F Superheat always refers to a vapor.

A

T

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4
Q

T/F All liquid must be vaporized for superheating to occur

A

T

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5
Q

Subcooling always refers to a liquid at a temperature _____ its saturation temperature for a given pressure.

A

Below

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6
Q

One main function of a compressor

A

Circulate refrigerant

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7
Q

One function of discharge line

A

Carry high pressure superheated vapor from compressor discharge valve to condenser

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8
Q

Receiver acts as a ____.

A

Surge tank

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9
Q

T/F Liquid line transfers low pressure subcooled liquid to metering device.

A

F high pressure

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10
Q

Meters liquid refrigerant from liquid line to evaporator

A

Metering device

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11
Q

The metering device is a restriction that separates high pressure side from _____ _____ _____ in refrigerant system.

A

Low pressure side

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12
Q

The evaporator, like the condenser, acts as a _____ _____.

A

Heat exchanger

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13
Q

_____ transports low pressure superheated vapor from evaporator to compressor.

A

Suction line

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14
Q

4 stages of refrigeration cycle

A

Expansion
Evaporation
Compression
Condensation

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15
Q

Superheat on the systems low side can be divided into 2 types:

A

Evaporator superheat

Total (compressor) superheat

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16
Q

What controls evaporator superheat?

A

TXV

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17
Q

Low evaporator loads can be caused by 4 things:

A

Iced up or dirty coil

Defrost circuit malfunction causing coil icing

End of refrigeration cycle

Low refrigerant charge

18
Q

When liquid refrigerant enters the compressor crankcase while compressor is running is called _____.

A

Flooding

19
Q

Name 2 things could cause slugging to occur?

A

Bad TXV

Low load

20
Q

3 metering devices

A

Thermostatic expansion valve (TXV)
Automatic expansion valve (AXV)
Capillary tube

21
Q

If the diameter is too small _____,

A

the evaporator will be starved.

22
Q

If a capillary tube is over/under charged, it will backup the excess liquid in the condenser causing high/low head pressure.

A

Over

High

23
Q

It is extremely important to install a filter drier before the capillary tube to catch any _____ _____.

A

Foreign objects

24
Q

3 main functions of TXV

A

Provide constant amount of evaporator superheat

Keep evaporator full of refrigerant

Prevents flood back of refrigerant to compressor

25
Q

Color codes

R11
R12
R134A

A

Blue
Yellow
Blue

26
Q

Air may enter refrigeration system because of what 3 things?

A

Tube, gasket or flange leaks

Poor charging procedures

Poor recovery or recycling procedures

27
Q

2 types of leak detection

A

Electronic

Ultraviolet (UV) Fluorescent

28
Q

What 2 things are detrimental to a refrigeration system?

A

Air

Moisture

29
Q

New and replacement compressors come shipped with dry nitrogen that needs to be removed and _____ prior to use.

A

Evacuated

30
Q

If the contamination from a burned out and or sludged compressor reaches a replacement compressor, the new compressor will probably _____.

A

Burn out

31
Q

The oil from a burn out can cause serious skin irritation and possible _____.

A

Burns

32
Q

When do you evacuate a compressor?

A

When it has been isolated from the rest of the system

33
Q

TEWI

A

Total Equivalent Warming Impact

34
Q

CAA

A

Clean Air Act

35
Q

The substances affected by the CAA were divided into __ main classes.

A

2

36
Q

Section 608 of the CAA prohibited individuals from knowingly _____.

A

Venting off refrigerant

37
Q

Recovery and recycling equipment manufactured after November 15, 1993 must be equipped with _____ fittings.

A

Low-loss

38
Q

Owners with charges greater than _____ are required to repair substantial leaks.

A

50 lbs

39
Q

How many types of EPA technician certifications are there?

A

4

40
Q

Why is it necessary to have superheat in a refrigeration system?

A

To ensure refrigerant is in a vaporized state.

AC Refrigeration (2 decks)

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