Split Systems

Question 1

Which gauge on the manifold gauge is considered to be the compound gauge?

Answer 1

The low side gauge (blue) is a compound gauge

Question 2

Name four main types of electronic leak detectors?

Answer 2

Ion source detection, thermistor type, halogen type, and ultrasonic type

Question 3

What is the difference between a recovery unit and a recycle unit?

Answer 3

Recycle units work in the same manner as the recovery units, but they take it one step further by adding filters and oil separators that remove any compressor oil, moisture, and some contaminants from the refrigerant

Question 4

What is the maximum capacity of any service or storage cylinder used for refrigerant?

Answer 4

Must not be filled 80 percent of its capacity

Question 5

What does reclaiming the a refrigerant mean?

Answer 5

It is cleaned and processed to new specifications

Question 6

Why should nitrogen be purged through the copper lines when they are being brazed?

Answer 6

To prevent oxidation

Question 7

How should we purge nitrogen through the copper lines when they are being brazed?

Answer 7

By allowing a small amount of nitrogen into the system at a very low pressure less than 2 psig.

Question 8

Which hoses are connected to each service valve?

Answer 8

The low pressure gauge (blue gauge) goes to the low pressure side of the system. The high pressure side (red gauge) goes to the high pressure side of the system. The centre hose in connected to the inlet port on the recovery unit.

Question 9

What color is the gauge on the low pressure gauge?

Answer 9

Blue

Question 10

What color is the gauge on the high pressure gauge?

Answer 10

Red

Question 11

To what pressure should the system be tested when dealing with refrigeration?

Answer 11

A pressure between 125 psi to 150 psi is considered safe for most systems.

Question 12

Removing the stem in the Schraeder valve speeds up the evacuation process. True or False?

Answer 12

True

Question 13

What amount of vacuum must be obtained to render the system free of refrigerant?

Answer 13

10” to 11” of Hg

Question 14

What are the two reasons for performing a deep evacuation?

Answer 14

To remove moisture, and to remove non-condensable gases

Question 15

When is a triple evacuation used?

Answer 15

If the system is deemed to be dirty or wet

Question 16

How many CFM is required for each ton of cooling?

Answer 16

Between 400 CFM to 425 CFM per ton of cooling

Question 17

What are the two methods of calculating the CFM in a system?

Answer 17

Calculating by temperature rise across the evaporator coil and calculating by static pressure across the evaporator coil.

Question 18

Which ways of calculating CFM is one of the most accurate?

Answer 18

The static pressure method

Question 19

Which method is used for checking the refrigeration charge on a system equipped with a TXV?

Answer 19

The method of checking for proper sub-cooling

Question 20

We as sheet metal workers are allowed to service and install cooling systems up to and including?

Answer 20

60 000 Btuh (5 tons)

Question 21

What are installed on all newer condensing units?

Answer 21

Both liquid line and suction line service valves are installed on newer units.

Question 22

What is a manifold gauge set used for?

Answer 22

To diagnose and service air-conditioning and refrigeration systems properly.

Question 23

What color is the centre hose manifold gauge usually?

Answer 23

Yellow

Question 24

What are the yellow hand valves on the manifold used for?

Answer 24

To perform recovery, evacuation and recharging procedures.

Question 25

What is the sight glass on the manifold used for?

Answer 25

It allows you to see if there is a liquid, gas bubbles, or vapour in the system.

Question 26

What should you always do when using gauge sets that were used on different refrigerants in order to avoid cross contamination?

Answer 26

Purge the lines with nitrogen

Question 27

Most copper tubing has a max pressure of?

Answer 27

700 PSI

Question 28

What are three styles of gauges used in the refrigeration field?

Answer 28

High pressure, vacuum, and compound gauges

Question 29

Always remember gauges should never be subjected to more than ____ of their full scale range on the gauge face.

Answer 29

75 percent

Question 30

Hoses are constructed to withstand pressures in excess of?

Answer 30

500 psi (burst pressure 2000 psi)

Question 31

Which color on the hoses is used for charging and evacuating?

Answer 31

Yellow or black

Question 32

All hoses must have?

Answer 32

Shut off devices to prevent the introduction of air into the system.

Question 33

When servicing air conditioning systems, what are the three ways of identifying the refrigerant?

Answer 33

Labels, service fittings, and using a refrigerant identifier

Question 34

Many refrigerants are ___ and ___.

Answer 34

Colourless and odourless

Question 35

What is the only way to test refrigerants?

Answer 35

By using a refrigerant identifier

Question 36

How do ion source leak detectors detect leaks?

Answer 36

By using the positively charged particles in the refrigerant

Question 37

What do halogen leak detectors only work on?

Answer 37

Halogen based refrigerants such as R-12 and R-22

Question 38

How do ultrasonic leak detectors detect leaks?

Answer 38

By picking up sounds that we cannot hear

Question 39

What is a recovery unit used for?

Answer 39

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

Question 40

Service cylinders are, for the most part reusable. True or False?

Answer 40

True

Question 41

What cylinder color is R-11?

Answer 41

Orange

Question 42

What cylinder color is R-12?

Answer 42

White

Question 43

What cylinder color is R-22?

Answer 43

Light green

Question 44

What cylinder color is R-134a?

Answer 44

Light blue (sky)

Question 45

What cylinder color is R-410a?

Answer 45

Rose

Question 46

What cylinder color is R-502?

Answer 46

Light purple (lavender)

Question 47

What are storage cylinders used for?

Answer 47

For the recovery, recycling, and reclaiming of refrigerant. They are the cylinders that you put the refrigerant into when you remove it from the cooling system.

Question 48

All storage cylinders must be?

Answer 48

Department of Transportation (DOT) approved

Question 49

What are vacuum pumps used for?

Answer 49

They are used to evacuate the closed refrigeration system into a deep vacuum. It removes any gas or moisture that may be in the system.

Question 50

Without a vacuum gauge, you take the risk of not dehydrating the system properly. True or False?

Answer 50

True

Question 51

A thermistor vacuum gauge contains which two elements?

Answer 51

A heater (filament) and a thermocouple junction that contacts the filament.

Question 52

What measurement is used for dehydration?

Answer 52

Microns

Question 53

How many microns do we want to boil and evacuate moisture in a refrigeration system?

Answer 53

500 microns

Question 54

What are refrigeration charging scales used for?

Answer 54

They are used to weigh in the accurate charge in a refrigeration system.

Question 55

What are two ways that nitrogen is used in a refrigeration system?

Answer 55

By flowing through copper to prevent it from forming oxides and to pressurize the system to test for leaks.

Question 56

Liquid in a refrigeration system is what kind of pressure?

Answer 56

High pressure

Question 57

Vapour in a refrigeration system is what kind of pressure?

Answer 57

Low pressure

Question 58

Pressure goes from ___ to ___?

Answer 58

High to low

Question 59

The preferred method of making a strong leak-free joint is?

Answer 59

Brazing with a silver based rod.

Question 60

What important to do before you braze any pipe?

Answer 60

Fit the pipe and clean it

Question 61

Oxide forms on copper if?

Answer 61

Air is present

Question 62

What is our enemy in refrigeration systems?

Answer 62

Oxidation

Question 63

What is our friend in refrigeration systems?

Answer 63

Nitrogen

Question 64

What rod is normally used for brazing cooling lines?

Answer 64

An alloy containing 5 to 15 percent silver and is commonly known as Silfos

Question 65

What should you do after a pipe is brazed?

Answer 65

Apply a wet rag or water to the joint

Question 66

What test should be done on all field installed systems?

Answer 66

The leak test which is done by filling the system with dry nitrogen.

Question 67

Laws prevent the release of ___ or ___ into the atmosphere.

Answer 67

CFC or HCFC refrigerants

Question 68

Where can you identify the type of refrigerant the system contains?

Answer 68

On the equipment rating plate

Question 69

What is one of the most common ways of compressor failure?

Answer 69

Lack of lubrication or overheating

Question 70

If components show evidence of icing during the recovery process, what can be done to fix that?

Answer 70

The components can be heated gently to speed up the flow of refrigerant by using a heat gun but never any type of open flame.

Question 71

What are the two reasons for a proper deep evacuation?

Answer 71

It removes non-condensable gases and it removes moisture.

Question 72

If you're using a vacuum pump in a refrigeration system and the gauge rises slowly to 1500 microns, what does this indicate?

Answer 72

That there is moisture in the system and the process must be repeated.

Question 73

If you're using a vacuum pump in a refrigeration system and the micron gauge steadily rises to atmospheric pressure, what does this indicate?

Answer 73

That there is a leak and it must be located and repaired.

Question 74

What steps are done to do a triple evacuation?

Answer 74

Evacuate the system to 1000 microns from both the service valves and hold for two hours, evacuate to 500 microns and hold for 2 hours minimum, and then evacuate the system to the lowest pressure (200 microns for two hours minimum).

Question 75

What is the reason for taking the system into a perfect vacuum?

Answer 75

As the pressure drops, the temperature at which water evaporates drops as well.

Question 76

What is super heat?

Answer 76

heat (a liquid) under pressure above its boiling point without vaporization.

Question 77

What is subcooling?

Answer 77

the difference between condensing pressure/temperature and liquid temperature at the expansion valve inlet.

Question 78

What is the difference between superheat and subcooling?

Answer 78

While superheat indicates how much refrigerant is in the evaporator (high superheat indicates not enough, low superheat indicates too much), subcooling gives an indication of how much refrigerant is in the condenser.

Question 79

What do most new split systems come with and how much?

Answer 79

A factory charge of refrigerant and a 15 to 25 feet of line set that is referred to as the default lengh.

Question 80

What must be done if the actual line set length is greater than the default length for which the manufacturer pre-charged the condenser?

Answer 80

Add refrigerant by weight to account for the actual line set length.

Question 81

Manufacturers recommend how much CFM per ton of cooling?

Answer 81

400 CFM to 425 CFM per ton of cooling

Question 82

What are the two most common methods to check for the proper CFM when calculating air flow?

Answer 82

By calculating temperature rise and by calculating static pressure across the evaporator coil.

Question 83

To calculate the CFM by the temperature rise method you must have?

Answer 83

The furnaces Btuh output, the temperature rise, and the formula CFM = furnace Btuh output divided by (1.08 x temperature rise)

Question 84

Temperature rise = ?

Answer 84

Supply air temperature - return air temperature

Question 85

How many readings must you take when using the static pressure method?

Answer 85

Two readings: one before and another after the evaporator coil

Question 86

When using the superheat chart always get the system down to the lower value and top up as much as you can. True or False?

Answer 86

True

Question 87

What must you do any time you make an adjustment to the amount of refrigerant in the system?

Answer 87

You must let it run for a minimum of 15 minutes to allow the system to stabilize.

Question 88

It is much easier to add refrigerant than it is to remove it. True or False?

Answer 88

True

Question 89

Superheat temperature measurements should be taken within how many feet of the compressor suction line connection?

Answer 89

3 feet

Question 90

Do not adjust charge based on superheat on systems with thermal expansion valves. True or False

Answer 90

True

Question 91

What must you do to determine sub-cooling?

Answer 91

Determine the high pressure reading on the gauge, and the temperature of the liquid as close to the evaporator as possible.

Question 92

Liquid line temperature at the evaporator should be within how many degrees of liquid line temperature at the condensing unit?

Answer 92

2 degrees

Question 93

Sub-cooling = ?

Answer 93

Saturation temperature - liquid line temperature