TPC 432

Question 1

If you increase the pressure of a liquid, its ____________ temperature will __________ , meaning that it will boil at a higher temperature.

Answer 1

Saturation; increase

Question 2

At a temperature of -30°F, the enthalpy of the saturated liquid refrigerant (h_f ) is 3.5 Btu/lb. The enthlapy of evaporation (h_fg ) is 87.4 Btu/lb. What is the enthalpy of the saturated vapor (h_g )?

Answer 2

90.9 Btu,lb

Question 3

A system must provide 8 tons of refrigeration. What horsepower is needed for this system? Choose values from the list below when making your calculations: Condensing pressure = 232 psia Evaporating pressure = 61 psia Refrigerating effect = 62 Btu/lb. Enthalpy of condenser pressure = 115 Btu/lb. Enthalpy at evaporator pressure = 98 Btu/lb. One ton of refrigeration = 200 Btu/min. One horsepower = 33,000 ft-lb/min = 42.4 Btu/min.

Answer 3

10.3 hp

Question 4

Liquid refrigerant can be subcooled by transferring heat either to the atmosphere in the condenser or to the ______ in the suction line heat exchanger.

Answer 4

Refrigerant vapor

Question 5

An “ideal” refrigerant has which of the following characteristics?

Answer 5

Nonflammable

Question 6

In the ASHRAE standard designations of refrigerants, the:

Answer 6

Letter R is being replaced by letters identifying the chemical structure

Question 7

Temperature glide occurs only in __________ refrigerants.

Answer 7

Blended

Question 8

ASHRAE classifies refrigerants according to how hazardous they are. The most hazardous refrigerants are rated __________.

Answer 8

B3

Question 9

When handling out and storing refrigerants, you must protect yourself by:

Answer 9

Avoiding any open flame

Question 10

The ozone layer in the earth’s atmosphere is important, because it:

Answer 10

Absorbs ultraviolet radiation from the sun

Question 11

CFCs contribute to the greenhouse effect by:

Answer 11

Absorbing infrared radiation

Question 12

In order to minimize the release of CFCs into the atmosphere, refrigeration service technicians must:

Answer 12

Recycle refrigerants on-site, if possible

Question 13

A recycled refrigerant may be placed in:

Answer 13

The system from which it was removed

Question 14

During the installation of a new system, the chance of future refrigerant leaks can be reduced by:

Answer 14

Installing a muffler in the compressor discharge line

Question 15

To reduce the depletion of the ozone layer, the U.S. government has implemented laws requiring the:

Answer 15

Testing and certification of all technicians whose work can cause the release of harmful refrigerants.

Question 16

The EPA’s final rule concerning the handling of refrigerants and refrigeration equipment requires:

Answer 16

Certifying the equipment used in recycling and reclaiming refrigerants

Question 17

The compressor for an active recovery system is part of the ______. The compressor for a passive recovery system is part of the _________.

Answer 17

Recovery equipment; system being serviced

Question 18

Technicians who work on residential air conditioning systems must have at least ______ certification.

Answer 18

Type II

Question 19

Which of the following documents is required by the EPA?

Answer 19

Certification activity report

Question 20

Which of the following is a contaminant that can be removed by a filter-drier?

Answer 20

Acid

Question 21

An absorption-type desiccant holds water by means of a(n) ________ action, but an adsorption-type desiccant holds water by means of a(n)_____ action.

Answer 21

Chemical; mechanical

Question 22

If you mount a filter-drier in a vertical suction line, the inlet should be located at the top so that ______ cannot become trapped inside.

Answer 22

Oil

Question 23

When selecting a filter-drier, you need to base your selection in part on the:

Answer 23

Minimum particle size it can trap

Question 24

When installing a filter-drier in a refrigeration system, you should:

Answer 24

Wear safety goggles

Question 25

You can pinpoint leaks in a new refrigeration system by charging the system with ________ and using a ________.

Answer 25

Nitrogen; soap solution

Question 26

When preparing to use a gauge manifold in servicing a pressurized refrigeration system, you connect its high-side charging hose to the:

Answer 26

Compressor discharge service valve

Question 27

To check the charge in a refrigeration system, you can look at the ________ in the liquid line. If the charge is low, you will probably see _______.

Answer 27

Sight glass; bubbles

Question 28

In using the deep-vacuum method of dehydrating a refrigeration system, you lower the pressure to about _________ microns or less. With the vacuum pump turned off, a gradual rise in pressure tells you the system is _______.

Answer 28

1,000; not dry

Question 29

You can tell whether you have charged a refrigeration system with the correct amount of refrigerant by checking the:

Answer 29

Weight of the refrigerant used

Question 30

The miscibility of a refrigerant oil is its ability to:

Answer 30

Mix with the refrigerant

Question 31

Oil that becomes mixed with the refrigerant in a system can cause which of the following problems?

Answer 31

Clogged desiccant

Question 32

An oil separator is located between the ______ and ______ in order to keep oil out of the condenser and evaporator.

Answer 32

Compressor; condenser

Question 33

Moisture in a refrigeration system causes a variety of problems, including:

Answer 33

Blockage in cold parts of the system

Question 34

Before you check the oil level in the sight- glass on a refrigeration compressor, you should stop the compressor for at least ______. The compressor should be ______ while you check the oil level.

Answer 34

Ten minutes; stopped