Mechanical For A/C Study Guide

Equal volumes of gases at equal pressures and temperatures contain equal numbers of molecules, regardless of the mass of the gases.

Avogadro's law

R-500 is a blend refrigerant of this type.

Azeotropic

If its temperature remains constant, the volume of a gas varies inversely to the pressure.

Boyle's Law

If its pressure remains constant, the volume of a given quantity of gas varies directly to its absolute temperature.

Charles' law

Refers to extremely low refrigerant temperatures.

Cryogenics

The total pressure of a confined mixture of gases is the sum of the pressure for each gas involved.

Dalton's law

Type of refrigerant that is used and then released to the atmosphere.

Expendable

A perfect vacuum is 0 psig. Select one: True False

False

Boyle's law states that the pressure of a gas increases if its volume also increases. Select one: True False

False

Carbon dioxide is classified as an organic refrigerant (600 series). Select one: True False

False

Cylinder color-coding is a requirement for manufacturers, so technicians do not need to check labels. Select one: True False

False

HCFCs have an ODP rating of 0. Select one: True False

False

HFCs were the first type of refrigerant to be produced. Select one: True False

False

Like gases, solids and liquids are compressible in most cases. Select one: True False

False

Service technicians can safely use formulas and tables to mix their own azeotropic refrigerant blends. Select one: True False

False

The refrigerant temperature in the evaporator is the same as the evaporator temperature when the unit is running. Select one: True False

False

At constant volume, the absolute pressure of a given quantity of a gas varies directly with its absolute temperature.

Gay-Lussac's law

Refrigerant with 0 ODP, low GWP, and high flammability, used in some new standalone refrigerators and freezer

HCs

Refrigerant with 0 ODP, low GWP, and low toxicity, used in some new automotive applications.

HFOs

Cylinder color code for R-22 cylinders.

Light green

Pressure applied upon a confined fluid is transmitted equally and undiminished in all directions.

Pascal's law

Refrigerant used as a replacement for R-11.

R-123

HFC refrigerant.

R-134a

Refrigerant used in absorption systems.

R-717

Unique characteristic of zeotropic blends.

Temperature glide

A gas expands to fill its container. Select one: True False

True

A higher coefficient of performance means that a refrigerant produces its refrigeration effect more efficiently. Select one: True False

True

A refrigerant blend containing an HCFC and a CFC is considered a CFC. Select one: True False

True

In a zeotropic refrigerant blend, the refrigerant with the lowest boiling point boils first. Select one: True False

True

Pressures below atmospheric pressure can be measured in inches of mercury column. Select one: True False

True

R-134a has been used as a replacement refrigerant for systems that use R-12. Select one: True False

True

R-22 and R-123 are classified as HCFC refrigerants. Select one: True False

True

According to the ASHRAE classification for refrigerants, the classification for the least toxic and least flammable refrigerants is ____. Select one: a. A1 b. B3 c. A3 d. B1

a. A1

Due to their high ozone depletion potential, ____ refrigerants were targeted first for phaseout by the Montreal Protocol. Select one: a. CFC b. HFC c. All of the above. d. HCFC

a. CFC

All recovery devices manufactured before november 15, 1993 for use with small appliances must meet which of the following requirements? Select one: a. Capable of recovering 80% of the refrigerant whether or not the compressor is operating or achieving a 4 inch vacuum under the conditions of ARI 740 b. Capable of recovering 70% of the refrigerant if the compressor is operating or achieving a 4 inch vacuum under the conditions of ari 740 c. Capable of achieving a 10 inch vacuum under the conditions of ARI740 d. No requirements, this equipment would be "grandfathered".

a. Capable of recovering 80% of the refrigerant whether or not the compressor is operating or achieving a 4 inch vacuum under the conditions of ARI 740

When air is trapped in an HVAC system's condenser, high-side pressure readings will be affected by the principles of ____ law. Select one: a. Dalton's b. Gay-Lussac's c. Charles' d. Boyle's

a. Dalton's

Portable refillable tanks or containers used to ship CFC or HCFC refrigerants obtained with recovery equipment must meet what standards? Select one: a. Department of Transportation b. Communit Right to know act c. Underwriters Laboratories d. All of the above

a. Department of Transportation

The principles of ____ law are demonstrated when volumes remains constant, but pressure and temperature rise and fall together. Select one: a. Gay-Lussac's b. Dalton's c. Charles' d. Boyle's

a. Gay-Lussac's

Which refrigerant is a chlorine free refrigerant Select one: a. HFC134A b. CFC12 c. HCFC22 d. HCFC124

a. HFC134A

Which zeotropic refrigerant blend is used as a replacement for R-22 in air-conditioning applications, but operates at a higher temperature and pressure? Select one: a. R-410A. b. R-600a. c. R-290. d. R-404A.

a. R-410A

After 1995 supplies of CFC refrigerant for equipment servicing will come from; Select one: a. Recovery and recycling b. solvent conversion c. European chemical manufacturers d. Third World Checmical manufactures

a. Recovery and recycling

When installing any type of access fitting onto a sealed system; Select one: a. The fitting should be leak tested before proceeding with recovery b. it is not necassary to leak test an access fitting c. The fitting need not be leak tested until the total repair is complete d. The system must be pressurized with dry nitrogen before leak testing can be attempted

a. The fitting should be leak tested before proceeding with recovery

The synthetic lubricant presently used with ternary blends containing hcfcs is Select one: a. alkylbenzene b. glycols c. esters d. whale oil

a. alkylbenzene

As a gas is compressed into a smaller space, ____ the gas. Select one: a. heat is added to b. volume is added to c. heat is removed from d. pressure is reduced on

a. heat is added to

In SI units, pressure above atmospheric pressure is primarily measured in ____. Select one: a. kilopascals b. millibars c. torr d. microns

a. kilopascals

Ozone in the stratosphere above the earth consists of Select one: a. mulecules containing 3 oxygen atoms b. molecules of 2 oxygen atoms c. radioactive particles d. pollutants that have risen from ground level

a. mulecules containing 3 oxygen atoms

Technicians receiving a passing grade on this small appliance examintation are certified to recover refrigerant during maintenance, service, or repair of; Select one: a. packaged terminal air conditioners with 5 pounds or less of refrigerant b. small centeral air-conditioning systems with 10 pounds of less of refrigerant c. low pressure equipment d. motor vehicle air-conditioning equipment

a. packaged terminal air conditioners with 5 pounds or less of refrigerant

Recovery equipment that relies upon the compressor in the applieance and/or the pressure of the refrigerant in the appliance would be considered; Select one: a. system dependent b. self-contained c. a packaged terminal unit d. self-sufficient

a. system dependent

When a refrigeration unit is off, the temperature of the condenser is ____ the temperature of the refrigerant. Select one: a. the same as b. more saturated than c. higher than d. lower than

a. the same as

An award of up to what amount may be paid to a person supplying information that leads to a penalty agains a technician who is intentially venting Select one: a. 5000 b. 10000 c. 25000 d. 50000

b. 10000

What is the maximum allowable factory charge of refrigerant for type 1 appliances Select one: a. 3 pounds b. 5 pounds c. 10 pounds d. 15 pounds

b. 5 pounds

When transporting cylinders containing used refrigerant DOT requires that you Select one: a. use osha approved containers b. attach DOT classification tags c. ship by epa certified carrier d. do all of the above

b. attach DOT classification tags

When transporting cylinders containing used refrigerant, DOT requires that you; Select one: a. use OSHA approved containers b. attach DOT classification tags c. ship by EPA certified carrier d. Do all of the above

b. attach DOT classification tags

When pressurizing a refrigerant system with nitrogen what rule should you always follow? Select one: a. charge nitrogen as a liquid b. charge through a pressure regulator c. pressurize to above 1000 pounds d. never use nitrogen inside the system

b. charge through a pressure regulator

One instance when personal protective equipment (gloves, safety glasses, safety shoes, etc) should be worn is; Select one: a. reporting for work b. handling and filling refrigerant cylinders c. climbing ladders d. lifting

b. handling and filling refrigerant cylinders

Pressure below atmospheric pressure is primarily measured in ____. Select one: a. psia b. inches of mercury c. psig d. inches of water column

b. inches of mercury

If EPA regulations change after a technician becomes certified; Select one: a. The technician certification is "grandfathered " for one year to allow time for recirtification. b. it will be the technicians responsibility to comply with any future changes in the law. c. a new certification test must be taken to be re-certified d. Both A and C

b. it will be the technicians responsibility to comply with any future changes in the law.

A cooling effect is produced when refrigerant enters an evaporator due to ____. Select one: a. air exchange b. pressure change c. state change d. verbal exchange

b. pressure change

Removing refrigerant in any condition from a system and storing it an external container without necessarily testing or processing it in any way defines Select one: a. recycling b. recovering c. reclaiming d. restoring

b. recovering

The cylinder color code for R-134a is ____. Select one: a. orange b. sky blue c. light green d. white

b. sky blue

If applied pressure on a saturated vapor is increased, then ____. Select one: a. Both of the above. b. some vapor will condense c. None of the above. d. some liquid will evaporate

b. some vapor will condense

When recovering refrigerant, it is important not to mix different refrigerants in the same container because; Select one: a. The mixture would explode b. the mixture may be impossible to reclaim c. the refrigerant mixture is toxic d. it is a violation of EPA environemental regulations

b. the mixture may be impossible to reclaim

The difference between absolute pressure and gauge pressure is ____. Select one: a. 29.92 psi b. 17.4 psi c. 14.7 psi d. 28 psi

c. 14.7 psi

A storage cylinder of recovered R500 at normal room temperature (about 75 degrees F in the absence of non-condensables will be pressurized to Select one: a. 30 psig b. 85 psig c. 93.5 psig d. 120 psig

c. 93.5 psig

The principles of ____ law are demonstrated when temperature remains constant, but pressure and volume express an inverse relationship. Select one: a. Charles' b. Gay-Lussac's c. Boyle's d. Dalton's

c. Boyle's

Which of the following gasaes help form the earth's protective shield? Select one: a. Methane b. Radon c. Stratospheric Ozone d. Carbon Dioxide

c. Stratospheric Ozone

Chlorofluorocarbons and hydroclorofluorocarbons have which of the following in common? Select one: a. They have the same ozone depletion potential b. They both contain hydrogen c. They must be recovered before opening or disposing of appliances d. They have the same saturation pressure at 70 degrees F

c. They must be recovered before opening or disposing of appliances

When checking for non-condensables inside a recovery cylinder, why should the technician allow the temperature of the cylinder to stabalize to room temperature before taking a pressure reading Select one: a. to prevent safety valves from purging refrigerant b. it is a quick method of determining refrigerant level inside the tank c. comparisons to a pressure temperature chart are only valid if both the pressures and temperature of the refrigerant are stable and known d. a temperature reading alone is enough to determine refrigerant quality

c. comparisons to a pressure temperature chart are only valid if both the pressures and temperature of the refrigerant are stable and known

A pressure-temperature curve shows that pressure and temperature are ____ in a refrigeration system. Select one: a. unrelated b. inversely related c. directly related d. irrelevant

c. directly related

The separation of the individual refrigerants in a zeotropic blend during phase change is known as ____. Select one: a. temperature glide b. wax separation c. fractionation d. viscosity

c. fractionation

If a refrigerant belongs to the 700 series in the refrigerant numbering system, then it is ____. Select one: a. methane based b. ethane based c. inorganic d. propane based

c. inorganic

The critical temperature of a substance is the highest temperature at which the substance may be in a ____ state, regardless of the pressure applied to it. Select one: a. solid b. gas c. liquid d. plasma

c. liquid

If applied pressure on a saturated vapor is decreased, then ____. Select one: a. some vapor will condense b. Both of the above. c. some liquid will evaporate d. None of the above.

c. some liquid will evaporate

If heat is added to a saturated vapor and raises the vapor's temperature above its boiling point, the heat is referred to as ____. Select one: a. saturated heat b. coefficient heat c. superheat d. latent heat

c. superheat

If a system will not hold a vacuum after it has been evacuated, then Select one: a. the system is ready to be charged b. the system has been adequately evacuated c. the system may be leaking d. an expansion valve is clogged

c. the system may be leaking

Refrigerants (R12, R22, R500, etc) in large quantities can cause suffication because Select one: a. They smell strong and make breathing difficult b. they are lighter than air and can cause dizziness c. they are heavier than air and displace oxygen d. they sting the nose and cause sneezing

c. they are heavier than air and displace oxygen

The ozone layer protects the earth from: Select one: a. nuclear radiation b. meteorites c. ultraviolet radiation from the sun d. infrared radiation from the sun

c. ultraviolet radiation from the sun

Evaporative cooling systems rely on the cooling effect derived from a ____. Select one: a. air exchange b. state change c. verbal exchange d. pressure change

c. verbal exchange

As a substance is heated, its ____ tends to increase. Select one: a. resistance b. conductance c. volume d. None of the above.

c. volume

A storage cylinder of recovered R22 at normal room temperatures (about 75 degrees F) in the absence of non-condensables, will be pressurized to Select one: a. 250 psig b. 200 psig c. 175 psig d. 130 psig

d. 130 psig

Concerning pressure, volume, and heat, if energy is added to a substance, then ____. Select one: a. volume may increase b. pressure may increase c. temperature may increase d. All of the above

d. All of the above

When operating refrigerant recovery or recycling equipment, the following precautions should be followed. Select one: a. Wear safety glasses b. wear protective gloves c. follow all safety precautions for the equipment d. All of the above

d. All of the above

When using recovery cylinders and equipment with schrader valves, it is critical to; Select one: a. Inspect the schrader valve core for bends and breakage b. Replace the damaged schraeder valve core to prevent leakage c. Cap the schrader ports to prevent accidental depression of the valve core d. All of the above

d. All of the above

Some state and local governments may establish laws that; Select one: a. follow the Clean Air Act/EPA regulations b. Are not as strict as the Clean Air Act/EPA regulations c. Contain stricter regulations that the clean air act/EPA regulations d. Both A and C

d. Both A and C

The principles of ____ law are demonstrated when pressure remains constant, but temperature and volume rise and fall together. Select one: a. Dalton's b. Gay-Lussac's c. Boyle's d. Charles'

d. Charles'

Ozone Depletion in the stratosphere is what type of problem Select one: a. Local b. Regional c. National d. Global

d. Global

Because they cannot be mixed with mineral oils, ____ refrigerants use synthetic oils for lubrication. Select one: a. CFC. b. HCFC. c. All of the above. d. HFC.

d. HFC

How many times can an expendable refrigerant be used? Select one: a. Twice. b. Ten times. c. Indefinitely. d. Once.

d. Once.

Factors affecting the speed of evacuation include Select one: a. the size of the equipment being evacuated b. the ambient temperature c. the amount of moisture in the system d. all of the above

d. all of the above

When using vapor recovery, the fill level of the recovery cyclinder can be controlled by; Select one: a. mechanical float devices b. electronic shut-off devices c. weight d. all of the above

d. all of the above

The system dependent recovery process for small appliances Select one: a. never needs the use of a pump or heat to recover refrigerant b. must use a pressure relief device when recovering refrigerant c. captures refrigerant in a non-pressurized container d. can only be performed on a system with an operating compressor

d. can only be performed on a system with an operating compressor

The component of a refrigeration system which changes a high pressure vapor to a high pressure liquid is the Select one: a. receiver b. metering device c. accumulator d. condenser

d. condenser

Hydroflourocarbon refrigerants contain; Select one: a. Chloring, flourine, carbon b. chlorine, flourine and hydrogen c. hydrogen, chlorine, and carbon d. hydrogen, flourine, and carbon

d. hydrogen, flourine, and carbon

Small pressure above or below atmospheric pressure is primarily measured in ____. Select one: a. psia b. inches of mercury c. psig d. inches of water column

d. inches of water column

All devices used for refrigerant recovery must Select one: a. be portable b. contain a heavy duty rain shield c. have a 20,000 btu/hr rating d. meet EPA standards

d. meet EPA standards

The lowest temperature at which a lubricant will flow is called the ____. Select one: a. flow point b. viscosity c. floc point d. pour point

d. pour point

According to the pressure formula, if area increases, then ____. Select one: a. volume decreases b. pressure increases c. volume increases d. pressure decreases

d. pressure decreases

According to the pressure formula, if force increases, then ____. Select one: a. area decreases b. area increases c. pressure decreases d. pressure increases

d. pressure increases

The sale of CFC and HCFC refrigerants is Select one: a. Banned b. limited by law to equipment owners c. allowed only if there is proof of need d. restricted to technicians who are epa certified in recovery

d. restricted to technicians who are epa certified in recovery

As applied pressure is raised on water, its boiling point ____. Select one: a. lowers b. remains the same c. None of the above. d. rises

d. rises