Refrigeration

Question 1

What are the 4 components in a basic air conditioning system?

Answer 1

Compressor
Evaporator
Condenser
Liquid metering device

Question 2

Which component absorbs heat?

Answer 2

Evaporator

Question 3

Define a cooling system?

Answer 3

It is a system that takes heat from where it is not wanted and relocates it to where it does not matter

Question 4

What percentage is relative humidity?

Answer 4

50%

Question 5

What percentage of liquid and vapour leave the metering device?

Answer 5

75% liquid

25% vapour

Question 6

What is the compressors job in a refrigeration cycle?

Answer 6

It pumps the refrigerant through the system by establishing the two pressure levels necessary for efficient operation of the system

Question 7

What happens to the refrigerant as it travels through the evaporator?

Answer 7

It enters as a liquid and leaves as a gas

Question 8

Name 3 types of condensers?

Answer 8

Air cooled
Water cooled
Evaporative

Question 9

Name 3 types of metering devices?

Answer 9

Thermostatic expansion valve (TXV)
Capillary tube
Orifices

Question 10

How is a TXV controlled?

Answer 10

By a sensing bulb attached to the piping on the discharge side of the evaporator

Question 11

How is a capillary tube used as a metering device?

Answer 11

It reduces pressure from the high side of the system to the low side because of its length and proper bore size

Question 12

Can a capillary tube be modified or adjusted?

Answer 12

No

Question 13

What type of metering device allows the system to equalize pressure when the compressor is off?

Answer 13

Orifice

Question 14

What type of piping is used in air conditioning?

Answer 14

Copper, type K-thick wall
Copper, type L-thin wall

Both are available in drawn temper which is hard or rigid and annealed temper which is soft or flexible

Question 15

What removes contaminants that may be present in the refrigerant stream?

Answer 15

A filter dryer

Question 16

How is a filter dryer installed?

Answer 16

With arrows pointing toward the direction of refrigerant flow

Question 17

How many btu’s per hour is needed to melt one ton of ice at 32 degrees?

Answer 17

12000 btu’s

Question 18

What is the atmospheric pressure at sea level?

Answer 18

14.7 psi

Question 19

What happens when a liquid is cooled below 0 degrees but does not change state to ice?

Answer 19

Sub cooling

Question 20

What happens to a liquid above 212 degrees F but does not change state to steam?

Answer 20

Super heat

Question 21

What happens to the temperature in refrigerant if you increase the pressure?

Answer 21

Temperature increases

Question 22

What happens to pressure in refrigerant if the temperature decreases?

Answer 22

Pressure decreases

Question 23

Where do you find the discharge line on a split system?

Answer 23

Between the compressor and condenser

Question 24

What is the line between the condenser and metering device called?

Answer 24

Liquid line

Question 25

The line from the evaporator to the compressor is known as what?

Answer 25

Suction or vapour line

Question 26

What size of system can licensed sheet metal workers install and service?

Answer 26

5 tons or 60000 btu’s

Question 27

What does CFC stand for?

Answer 27

Chlorofluorocarbon

Question 28

What capacity should a recovery cylinder be filled to?

Answer 28

80% maximum

Question 29

When the refrigerant leaves the condenser it is a hot, high pressure?

Answer 29

Liquid

Question 30

How many pressure changes will a refrigerant undergo in a complete cycle?

Answer 30

Two-liquid to vapour

Question 31

What happens to the temperature of refrigerant if it is released into the atmosphere?

Answer 31

It drops instantly

Question 32

What removes moisture from the air by condensing the moisture onto a cold surface?

Answer 32

Dehumidifier

Question 33

What components are found on the high side of the system?

Answer 33

Discharge side of compressor, condenser and piping to the metering device

Question 34

What components are found on the low side of the system?

Answer 34

Discharge side of metering device, evaporator, piping to the compressor and the inlet side of the compressor

Question 35

What is found in a compressor to help cool it?

Answer 35

Oil- either mineral in older systems or synthetic in newer systems

Question 36

What type of metering device distributed evenly across the coil?

Answer 36

Orifice

Question 37

What PPE is recommended when dealing with refrigerant?

Answer 37

Gloves, glasses and face shield

Question 38

What is the temperature on the low pressure side?

Answer 38

40-45 degrees F

Question 39

What is the temperature on the high pressure side?

Answer 39

110-115 degrees F

Question 40

The amount of heat a substance holds is?

Answer 40

Enthalpy

Question 41

The speed at which heat is released is?

Answer 41

Entropy

Question 42

What is the temperature of supply air?

Answer 42

55 degrees F

Question 43

Give 3 examples of an ideal refrigerant?

Answer 43

Latent heat of vaporization should be high It should not burn or be explosive It should evaporate at a low temperature and pressure It should condense at a medium temperature and pressure Must not be harmful to machinery Should not be toxic

Question 44

Why is a TXV the most commonly used valve?

Answer 44

It is the most efficient

Question 45

What is the greatest method of heat transfer?

Answer 45

Conduction

Question 46

Where should a filter drier be installed?

Answer 46

In the liquid line leaving the condenser

Question 47

What is the sequence for refrigerant entering the evaporator?

Answer 47

Refrigerant enters as a high pressure liquid at the expansion valve, moves in one direction through the coil, reaches the sensor for super heat and leaves as a low pressure vapour

Question 48

When must the filter drier be replaced?

Answer 48

Whenever the refrigeration system needs to be opened for service

Question 49

How is pressure defined?

Answer 49

As force per unit area P=F/A Measured in psi

Question 50

How is a refrigerant defined?

Answer 50

As a substance used for heat transfer. It absorbs heat by evaporating at a low temperature and pressure and releases the heat by condensing at a high temperature and pressure

Question 51

When exposed to an open flame, what do refrigerants contain and what can they produce?

Answer 51

They contain fluorocarbons that break down to produce dangerous poisonous vapours

Question 52

In what 2 components is there a change in temperature of the refrigerant?

Answer 52

Compressor and liquid metering device

Question 53

In what two components is there a change in state of the refrigerant?

Answer 53

Evaporator-liquid to gas | Condenser-gas to liquid

Question 54

Where is pressure at or above condensing pressure in the cycle?

Answer 54

On the high side

Question 55

Where is pressure at or below vaporizing pressure in the cycle?

Answer 55

On the low side

Question 56

Where is the sensing bulb on a TXV located?

Answer 56

The piping leaving the evaporator

Question 57

How many BTU’s are required to change the state of water from a solid to a liquid (latent heat of fusion)?

Answer 57

144 BTU’s

Question 58

How many BTU’s are required to change the state of water from liquid to a gas?

Answer 58

970 BTU’s

Question 59

Which refrigerants are considered the most harmful?

Answer 59

CFC’s