Modern Refrigeration and

1
Modern Refrigeration and Air Conditioning
Althouse Turnquist Bracciano
PowerPoint Presentation by Associated Technical
Authors
PublisherThe Goodheart-Willcox Company,
Inc.Tinley Park, Illinois
2
Chapter 9
Refrigerants
3
Learning Objectives

• Understand the differences between CFCs, HCFCs,
  and HFCs.
• Correctly identify and classify common
  refrigerants by their numbers.
• List the necessary properties of refrigerants.
• Read a pressure-temperature curve and identify
  the proper refrigerant.
• Demonstrate ability to read pressure-enthalpy
  diagrams.

4
Learning Objectives

• Discuss properties of different refrigerants and
  their applications in a system.
• Demonstrate handling of refrigerant cylinders and
  identify color codes.
• Follow approved safety procedures.
• Identify the safety procedures for using
  refrigerant cylinders.

5
Ozone
9.1

• Contained in a thin layer of Earths upper
  atmosphere.
• Protects living things on earth from the damaging
  effect of the Suns rays.

6
Chlorofluorocarbons(CFCs)
9.1.2

• Contained in some refrigerants, such as R-11,
  R-12, and R-13.
• Scientists have found that CFCs destroy the ozone
  layer.

7
EPA EnvironmentalProtection Agency
9.1.2

• Identifies the types of refrigerants that can be
  produced.
• Regulates how refrigerants will be used.

8
Four Classificationsfor Refrigerants
9.1

• Chlorofluorocarbons (CFCs).
• Hydrochlorofluorocarbons (HCFCs).
• Hydrofluorocarbons (HFCs).
• Refrigerant blends (azeotropic and zeotropic).

9
Identifying Refrigerants
9.1.1

• By number system following the letter R (for
  refrigerant).
• By color code (on cylinder).

10
Identifying Refrigerants
9.1.1
CFC, HFC, and HCFC refrigerants
11
Identifying Refrigerants
9.1.1
Zeotropic and azeotropic refrigerants
12
CFC (Chlorofluorocarbon) Refrigerants
9.1.2

• First refrigerants to be developed.
• Composed of chlorine, fluorine, and carbon.
• Low in toxicity and noncorrosive.
• Nonflammable and nonexplosive (but should not be
  released where flame or electric heating element
  is present).
• Heat causes CFCs to break down into their
  elements, releasing compounds such as phosgene
  gas (extremely harmful to the respiratory
  system).

13
CFC (Chlorofluorocarbon) Refrigerantscontinued
9.1.2

• Common CFCs include R-11, R-12, R-113,
  R-114,R-115, R-500, R-502, and R-503.
• Azeotropic mixtures classified as CFCs include
  R-500, R-502, and R-503.
• Believed to be major cause of ozone depletion.
• By international agreement, not manufactured
  since 1995.
• Laws forbid release of CFCs to the atmosphere.
• Recovery and recycling equipment required when
  reclaiming CFCs.

14
HCFC (Hydrochlorofluorocarbon)Refrigerants
9.1.3

• Molecules composed of methane or ethane in
  combination with a halogen such as R-22 and
  R-123.
• Causes less ozone depletion due to a smaller
  percentage of chlorine.
• Reduced potential for global warming.
• EPA requires phase-out of HCFCs by year 2030.

15
HFC (Hydrofluorocarbon)Refrigerants
9.1.4

• Contain one or more hydrogen atoms and no
  chlorine atoms.
• Possess zero potential for ozone depletion.
• Only a slight effect on global warming.
• Includes R-134a and R-23.
• When using R-134a in a retrofit system,
  adaptations (hardware changes, lubricant changes,
  etc.) must be made.

16
Questions

• Which refrigerant is most harmful to the ozone
  layer?

CFCs (chlorofluorocarbons)

• Name two chlorofluorocarbon refrigerants.

R-11 and R-12.

• Who regulates refrigerants and how refrigerants
  are handled?

The Environmental Protection Agency (EPA).

• How are refrigerants identified?

By number and color code.
17
Questions continued

• What happens to CFC refrigerants if they are
  exposed to heat?

They break down into their elements, such as
phosgene gas.

• Name two azeotropic mixtures.

R-500 and R-502.

• Name two HCFC refrigerants.

R-22 and R-123.

• Name one HFC refrigerant.

R-134A.
18
Refrigerant Blends(Azeotropic-Zeotropic)
9.1.5

• Azeotropic blends do not change or separate in
  composition in the refrigeration system.
• Zeotropic blends change composition and
  saturation when used in a refrigeration system.

19
Requirements for Refrigerants
9.2

• Must follow standards set by EPA.
• Nontoxic and nonpoisonous.
• Nonexplosive.
• Noncorrosive.
• Nonflammable.
• Make leaks easy to detect.
• Operate under low pressure (have a low boiling
  point).

20
Requirements for Refrigerants
9.2

• Stable as a gas.
• Permit refrigerator or compressor parts moving in
  the fluid to be easily lubricated.
• Have a high liquid volume per pound.
• Have low vapor volume per pound.
• Have as little pressure difference as possible
  between evaporating pressure and condensing
  pressure.
• Meet requirements of all current EPA rules and
  regulations.

21
Comparison of Refrigerants
9.2

• Based on specific evaporating and condensing
  temperatures.
• Evaporating temperature of 5F (15C).
• Condensing temperature of 86F (30C).

22
Pressure-Temperature Curves
9.3

• Vertical scale is temperature in F.
• Horizontal scale is pressure in psig.
• Temperature shown is always the temperature of
  the refrigerant.
• Same curve may be used to determine condensing
  and evaporating temperatures and pressures.

23
Pressure-Temperature Curves
9.3
24
Standard Evaporator andCondenser Temperatures
9.3.1
Pressure-enthalpy diagram of an ideal
refrigeration system does not note pressure
drops through evaporator and condenser coils or
inefficiencies of a compressor.
25
Grouping and Classificationof Refrigerants
9.4

• Toxicity Ability to be harmful or lethal with
  acute or chronic exposure (contact, inhalation,
  or ingestion).
• American Society of Heating, Refrigerating, and
  Air Conditioning Engineers (ASHRAE) classifies
  the toxicity of a refrigerant by letter A or B.
• Class A refrigerants are not identified as having
  a toxicity level.
• Class B refrigerants have an identified toxicity
  level.

26
Grouping and Classificationof Refrigerants
9.4

• Flammability Ability to ignite.
• Number indicates flammability classification.
• Group 1 no flammability identified
• Group 2 low flammability
• Group 3 high flammability

27
Grouping and Classificationof Refrigerants
9.4
28
Class A Refrigerants
9.5

• May be used in the largest quantities in any
  installation.
• Includes R-11, R-12, R-22, R-134a, and others.

29
R-11 Trichlorofluoromethane
9.5.1

• Synthetic chemical.
• Stable, nonflammable, and nontoxic.
• Considered a low-pressure refrigerant.
• Used in large centrifugal compressor systems.
• Leaks detected using a soap solution, halide
  torch, or electronic detector.
• Cylinder code color is orange.
• Being replaced by R-123 due to EPA rulings on
  CFCs.

30
R-12 Dichlorodifluoromethane
9.5.2

• Used in most domestic refrigeration and
  automotive air conditioner applications prior to
  1997.
• Production stopped in U.S. in 1997.
• Limited supply exists for service.
• Colorless, odorless liquid.
• Low latent heat value.
• Boiling point of 21.7F (29.8C).
• Had been used in reciprocating, rotary, and large
  centrifugal compressors.
• Leak detected by soap solution, halide torch,
  colored dye added to system, or electronic leak
  detector.

31
R-22Chlorodifluoromethane
9.5.3

• HCFC synthetic refrigerant.
• Developed for installations needing low
  evaporating temperature.
• Used successfully in air conditioning units,
  window air conditioners, nonindustrial heat
  pumps, and positive displacement chillers.
• Used with both reciprocating and centrifugal
  compressors.

32
R-22Chlorodifluoromethane continued
9.5.3

• Stable, nontoxic, noncorrosive, nonirritating,
  nonflammable.
• Boiling point of 41F (40.5C).
• Mixes readily with water desiccants should be
  used.
• Detect leaks with soap solution, halide torch, or
  electronic leak detector.

33
Questions

• Which type of refrigerant changes its composition
  as it is released from its container as a gas?

Zeotropic refrigerants.

• On a pressure-temperature curve, what is the
  horizontal scale used for?

psig

• Which classification of refrigerant is most toxic?

Class B refrigerants.

• Which group of refrigerants is most flammable?

Group 3.
34
Questions continued

• What is the color code for R-11?

Orange.

• Which refrigerant is replacing R-11?

(HCFC) R-123.

• What is the boiling point of R-12 at atmospheric
  pressure?

21.7F (29.8C) at atmospheric pressure.

• Which refrigerant is most commonly used on
  air-conditioning equipment?

R-22.
35
R-134a Tetrafluoroethane
9.5.4

• HFC refrigerant.
• Used as replacement for R-12.
• Used in centrifugal, reciprocation, rotary screw,
  and scroll compressors.
• Used as standard refrigerant in automotive air
  conditioning.
• Nontoxic, noncorrosive, and nonflammable.

36
R-134a Tetrafluoroethane continued
9.5.4

• Boiling point of 14.9F (26.1C).
• Not compatible with mineral-based oils. Must use
  polyol ester (POE) for most domestic
  refrigeration applications and polyalkylene
  glycol (PAG) for automotive system use.
• Leaks are detected by soap solution or
  fluorescent dyes, ultrasonic leak detectors,
  halogen-selective detectors, and other electronic
  leak detectors.

CAUTION Exposure to concentrations over 75,000
ppm may cause cardiac irregularities.
37
Systems Using R-134a as a Replacement for R-12
9.5.4

• Required design changes include 30 increase in
  condenser and evaporator sizing, change in
  desiccant, smaller hoses, and 30 increase in
  control pressure regulators.

38
Azeotropic Refrigerants
9.5.5

• Multicomponent working fluid.
• At atmospheric pressure, composition will not
  change when it evaporates or condenses.
• R-500 and R-502 are azeotropic refrigerants.

39
R-500
9.5.5

• Consists of 26.2 R-152a and 73.8 R-12.
• Used in industrial and commercial applications.
• Used only in systems with reciprocating
  compressors.
• Fairly constant vapor-pressure temperature curve.
• Leaks detected using halide leak detectors,
  electronic leak detectors, soap solution, or
  colored tracing agents.
• Water is soluble with this refrigerant use of
  driers recommended.
• Boiling point of 28F (33C) at atmospheric
  pressure.

40
R-502
9.5.5

• Consists of 48.8 R-22 and 51.2 R-115.
• Nonflammable, noncorrosive, practically nontoxic.
• Useful for obtaining medium and low temperatures
  0F to 60F (18C to 51C).
• Used in frozen food lockers, frozen food display
  cases, etc.
• Used with reciprocating compressors.

41
R-502
9.5.5

• Boiling point 50F (45.5C) at atmospheric
  pressure.
• Combines many of the best properties of R-12 and
  R-22.
• Leaks detected with soap solution, halide torch,
  or electronic leak detector.
• Cylinder code color is orchid.
• R-507A and R-125 are used to replace R-502.

42
R-503
9.5.5

• 40.1 R-23 and 59.9 R-13.
• Nonflammable, noncorrosive, and practically
  nontoxic.
• Boiling temperature is 126F (87.7C).
• Low-temperature refrigerant good for use in the
  low section of a cascade system.
• Leaks detected using a halide torch, soap
  solution, or electronic leak detector.
• Applications require extreme dryness or may
  result in ice formation.

43
R-503
9.5.5
44
R-507A
9.5.5

• 50 R-125 and 50 R-143a.
• HFC refrigerant used for low- and medium-
  temperature applications as replacement for
  R-502.
• Colorless, nonflammable, and has a slight odor.
• Boiling point of 52.1F (46.7C).
• Use polyol ester oil as lubricant.
• Color code is teal blue.
• Leaks detected by soap solution, electronic leak
  detector, halogen detector, and fluorescent leak
  detector.

45
Zeotropic Refrigerants
9.5.6

• Working fluids with two or more components.

CAUTION These are patented refrigerants. Never
attempt to make such mixtures.
46
R-401A
9.5.6

• Zeotropic blend of 53 HCFC-22, 13 HFC-152a, and
  34 HCFC-124.
• An alternative for CFC-12.
• Used in most medium-temperature systems, such as
  walk-in coolers, food display cases, etc.
• Cylinder color code is coral red.
• Can be used with alkyl benzene (AB), polyol ester
  (POE), or other oil mixtures, as indicated by
  manufacturer.
• Leaks detected by halogen detector,
  compound-selective detectors, or fluorescent
  additive.

47
R-406A
9.5.6

• Zeotropic blend of 55 R-22, 4 R-600a
  (isobutane), and 41 R-142b.
• An HCFC refrigerant, compatible with R-12
  systems.
• Soluble in mineral and alkyl benzene oils.
• Check with equipment manufacturer for suitability
  when using as an alternate refrigerant.
• Cylinder color code is light gray-green.

48
Group B Refrigerants
9.6

• Toxic!
• Harmful or lethal!
• Acute or chronic exposureby contact, inhalation,
  or ingestionmust be avoided!

49
Pressure-temperature Curves
9.6
Pressure-temperature curves for some Group B
refrigerants.
50
R-123Dichlorotrifluoroethane
9.6.1

• Used as a replacement for R-11.
• Used in centrifugal compressors and in
  foam-blowing applications.
• Colorless, odorless, and nonflammable liquid.
• Boiling point of 82.2F (27.9C).
• Compatible with mineral oil and alkyl benzene
  oil.
• Color code is light gray.

51
R-717 Ammonia
9.6.2

• Chemical compound of nitrogen and hydrogen.
• Colorless gas under ordinary conditions.
• Boiling temperature is 28F (33C).
• Low boiling point allows for refrigeration at
  temperatures well below zero.

CAUTION R-717 is somewhat flammable. With the
proper proportion of air, it will form an
explosive mixture.
52
R-717 Ammonia continued
9.6.2

• CAUTION The effect of ammonia on the respiratory
  system is violent!
• CAUTION Always stand to one side when operating
  an ammonia valve. A small valve stem leak may
  burn and damage eyes. Instant loss of
  consciousness may occur.
• CAUTION Wear a tight-fitting respirator.
• To detect R-717, a sulfur candle or sulfur spray
  vapor will produce white smokelike fumes.
• CAUTION When using or handling ammonia, follow
  the safety code provided by the International
  Institute of Ammonia Refrigeration.

53
R-717 Ammonia continued
9.6.2

• R-717 attacks copper and bronze in the presence
  of a small amount of moisture.
• Used in large compression machines having
  reciprocating compressors and in many
  absorption-type systems.

54
Questions

• Which HFC refrigerant is the replacement for R-12?

R-134A

• What type of oil must be used with R-134A?

Polyol ester (POE).

• Which azeotropic refrigerants are used for
  low-temperature systems?

R-502 and R-503.

• Which azeotropic HFC refrigerant is used as a
  replacement for R-502?

R-507A.
55
Questions continued

• Which type of refrigerant is R-401A, an
  azeotropic or a zeotropic blend?

Zeotropic blend.
R-12.

• Which refrigerant does R-401A replace?

• Which highly toxic refrigerant is a replacement
  for R-11?

R-123.

• What is the chemical composition of ammonia?

Nitrogen and hydrogen (NH3).

• Which metals cannot be used with R-717?

Copper, brass, or bronze.
56
Combustible Refrigerants
9.7
CAUTION Some refrigerants may form a flammable
material when mixed with air!

• The ASHRAE Safety Classifications are 2 (low
  flammability) or 3 (high flammability).
• Refrigerants in these categories include R-406A
  and R-717.
• Includes methylene chloride R-30, methyl
  chlorideR-40, methane R-50, ethane R-170,
  propane R-290, zeotropic mixtures (R-22, R-600a,
  and R142b),R-406A, butane R-600, and ammonia
  R-717.

57
Expendable Refrigerants
9.8

• Expendable refrigerants cool a substance or
  evaporator and are then released to the
  atmosphere.
• Systems using expendable refrigerants are
  referred to as chemical refrigeration or
  open-cycle refrigeration systems.
• Refrigerants of this type have a low boiling
  temperature.
• Include liquid nitrogen R-728, liquid helium
  R-704, and carbon dioxide R-744.

58
Water as a Refrigerant
9.9

• Water is never used in the compression-cycle
  refrigerating mechanism.
• Water is used in steam jet refrigeration for air
  conditioning systems.

59
Cryogenic Fluids
9.11

• Range in temperature from 250F (157C) to
  absolute zero (459.69F or 273C). This is
  referred to as the cryogenic range.
• Common cryogenic fluids are hydrogen R-702,
  helium R-704, neon R-720, nitrogen R-728, air
  R-729, oxygen R-732, and argon R-740.
• Containers for cryogenic fluids must be heavily
  insulated the temperature of the fluids inside
  is very low.

60
Cryogenic Fluids continued
9.11

• CAUTION Do not use these fluids in any container
  or mechanism that was not designed for such use.
• CAUTION Cryogenic fluids must never touch the
  skin since this will result in immediate freezing
  of the flesh. When handling cryogenic fluids, the
  entire body must be protected.

61
Refrigerant Cylinders
9.12

• Regulations for cylinders are prescribed by the
  Department of Transportation (DOT). There are
  three types of cylinders
• Storage cylinders.
• Returnable service cylinders.
• Disposable cylinders.

62
Storage Cylinders
9.12.1

• Must be dated and stamped with a DOT stamp.
• May not be used beyond six years from date shown.
• Must be returned to manufacturer every six months
  for checking.
• Cylinder valves are of the one-way type.
• Keep packing nut tight unless the valve is being
  used.
• Seal opening with a plug or cap when not in use.

CAUTION Use a hoist to lift and move cylinders
weighing over 35 pounds.
63
Service Cylinders
9.12.2

• Small, refillable cylinders (4 lbs. to 25 lbs.)
  can be carried by the technician.
• Cylinder valve fitted with 1/4" male flare.
• Liquid refrigerant expands with an increase in
  temperature.
• Weigh service cylinders before and after filling.
• Cylinders completely filled with cold or cool
  refrigerant will burst if warmed up.

CAUTION Never completely fill a cylinder with
liquid refrigerant! Allow space for
expansion. A safe limit is 80 full.
64
Returnable Service Cylinders
9.12.2

• Refrigeration supply houses provide service
  cylinders on an exchange basis.
• A liquid-vapor valve is available. It allows
  charging as a vapor or liquid without inverting
  the cylinder.

65
Returnable Service Cylinders
9.12.2
66
Returnable Service Cylinders
9.12.2
67
Disposable Cylinders
9.12.3

• Contain small quantities of refrigerant, from a
  few ounces to 50 lbs.
• Eliminates the need for refilling.
• Most are fitted with relief valves located in the
  valve body.

CAUTION Never recharge a disposable cylinder. Do
not use a disposable cylinder to store
refrigerant removed from a system.
68
Disposable Cylinders
9.12.3
69
Questions

• Name two combustible refrigerants.

R-290 (propane) and R-600 (butane).

• Which group of refrigerants is highly flammable?

Group 3.

• Where are expendable refrigerants used?

In open-cycle refrigeration systems.

• Name three expendable refrigerants.

Liquid nitrogen, liquid helium, and carbon
dioxide.
70
Questions continued

• What is the temperature range for cryogenic
  refrigerants?

The temperature range is from 250F (157C) to
absolute zero 459.69F (273C).

• Which organization approves storage cylinders?

Department of Transportation (DOT).

• Which type of cylinder must never be refilled?

A disposable cylinder.
71
Pressure-Temperature Tables
9.13

• Display the pressure-temperature relationship of
  a refrigerant under saturated conditions.
• Latent heat, specific heat, and density of liquid
  are shown.
• Find the temperature being investigated in the
  vertical left-hand column. Move across the
  columns horizontally to find the pressure.

72
Head Pressures (High Side)
9.14

• Pressures vary with refrigerants.
• Air-cooled condenser high-side temperature should
  be between 30F (17C) and 35F (19C) higher
  than the ambient temperature.
• Water-cooled condenser high-side temperature
  should be 15F (8C) to 20F (11C) above the
  exhaust temperature of the water.
• Condensing temperature will rise until the heat
  loss from the condenser equals the heat input to
  the condenser.

73
Causes for Above-Normal Head Pressures
9.14

• Air trapped in the condenser.
• Overcharge of refrigerant in systems with a
  low-side float, expansion valve, or thermostatic
  expansion valve.
• Blockage or poor water flow in condenser.
• Restriction in system, such as clogged capillary
  tube or stuck refrigerant control.
• Above normal low-side pressure.

74
Refrigerator Temperatures
9.15

• Cabinet temperatures are fairly standard.
• Must have correct-size evaporator for the
  temperature desired.
• Refrigerant will be 10F (6C) colder than the
  evaporator temperature when unit is running.
• Refrigerant and evaporator will become the same
  temperature during the off cycle.

75
Refrigerant Applications
9.16

• Manufacturer determines type of refrigerant used
  in a unit.
• Considerations in selection of refrigerant
  include
• System capacity.
• Volume of the vapor pumped.
• Latent heat of the refrigerant.
• Operating temperatures required.
• Size of the equipment.

76
Changing/Identifying Refrigerants
9.17

• Retrofitting Changing the type of refrigerant in
  a unit.
• Check manufacturers tags on the equipment.
• When retrofitting, contact manufacturer to see if
  components must be modified.
• Note Always use the proper recovery/recycle
  equipment when changing refrigerants.

CAUTION Do not sniff refrigerant this can be
deadly!
77
Amount of RefrigerantRequired in a System
9.18

• Varies with type of system.
• Low-side float, automatic expansion valve, and
  thermostatic expansion valve systems are not
  sensitive to amount of refrigerant charge.
• High-side float systems and capillary tube
  systems are very sensitive to amount of
  refrigerant charge.
• Sight glass in liquid line allows for
  determination of sufficient amount of
  refrigerant.
• Bubbles in sight glass mean charge is low.

78
Refrigeration Oil
9.19

• Circulates through system with refrigerant.
• Provides lubrication and cools compressors
  moving parts.
• Must withstand extreme temperatures.
• Oil removed from a system should be clear.
• If oil removed is discolored, new driers and
  filters should be placed in system.
• Use only oil recommended by manufacturer.
• Keep oil containers tightly sealed.

79
Properties of aGood Refrigerant Oil
9.19

• Low wax content.
• Good thermal stability.
• Good chemical stability.
• Low pour point.
• Low viscosity.

80
Moisture in Refrigerant
9.20

• May freeze at the refrigerant control.
• May cause refrigerant to break down and form
  harmful acids.
• A moisture indicator placed in the liquid line
  may detect moisture in a system.
• If moisture is noted, a new filter-drier should
  be installed.
• It may be necessary to replace the drier several
  times to remove sufficient moisture.
• When servicing, avoid exposing cold internal
  parts to air.

81
Safety
9.21

• Wear goggles and gloves at all times, especially
  when charging or discharging refrigerant.
• Liquid refrigerant may freeze the skin. Wash with
  water, treat for frostbite, and refer to a
  doctor.
• Refrigerants R-717 and R-764 are very irritating
  to the eyes and lungs. Avoid exposure to them.
• Refrigerant oil in hermetic compressors may be
  acidic. Never allow it to touch the skin.
• If a leak is suspected, thoroughly ventilate the
  room prior to working on the unit.

82
Safety continued
9.21

• Many refrigerants are heavier than air and will
  replace the air in a room. This is VERY
  dangerous! Instruments are available to warn if
  oxygen content is below a safe level.
• Sniffing refrigerant can cause death.
• Always use proper recovery/recycle equipment when
  changing refrigerants.
• Always check for recommended operating pressures
  for each refrigerant.
• To avoid mixing refrigerants, check the R-number
  prior to charging.

83
Safety continued
9.21

• There must be no lighted flames near a system
  suspected of a fluorocarbon refrigerant leak.
• Always charge refrigerant vapor into the low side
  of the system.
• Moisture should not be allowed to enter a
  refrigerating system.
• Containers of oil must be kept tightly sealed.
• Never fill a service cylinder more than 80 full.
• Always check the DOT cylinder stamp to be sure
  the cylinder is safe.
• Store refrigerant cylinders in a cool, dry place.

84
Questions

• On an air-cooled condenser, how high is the
  operating condenser temperature when compared to
  ambient temperature?

30ºF (17C) to 35ºF (19C) degrees higher.

• On a water-cooled condenser, how high is the
  operating condenser temperature when compared to
  the leaving water?

15ºF (8C) to 20ºF (11C) degrees higher.

• Name three possible causes for high head pressure.

Overcharged system, blocked airflow over the
condenser, air trapped in the condenser.
85
Questions continued

• Bubbles in a sight glass are usually an
  indication of

A low refrigerant charge.

• Does the oil in the compressor circulate with the
  refrigerant during the on cycle?

Yes.

• Which of the following is a good property of
  refrigerant oil, low viscosity or high viscosity?

Low viscosity.

• Name two problems that moisture can cause in a
  refrigeration system.

The formation of acids and freeze up at the
refrigerant control.
86
Glossary

• flammability
• Tendency to ignite.
• ozone
• A form of oxygen having three atoms to the
  molecule. The ozone layer is the outermost layer
  of the earths atmosphere. It absorbs ultraviolet
  light from the sun and shields the lower layers
  and the earth from harmful rays.
• retrofit system
• Updating of an existing system to new standards.
• retrofitting Changing the type of refrigerant in
  a system.
• toxicity
• Measure of the amount of poison in a substance
  or the amount of harm it can cause.