Modern Refrigeration and AC

Question 0

When liquid refrigerant enters the evaporator, the refrigerant is suddenly at a (High Temp and High Press, Low Temp and High Press, Low Temp and High Press or High Temp and Low Press)?

Answer 0

At a low pressure and a high temp

Question 1

What is used to control the capacity of a commercial compressor?

Answer 1

Unloaders

Question 2

All of the following effect the capacity of a TXV (thermostatic expansion valve) except an ____________ ________________.

Answer 2

An external equalizer

Question 3

What system uses a silicone carbide igniter?

Answer 3

Hot surface

Question 4

What is the process of expanding or enlarging a copper tube to receive another copper tube?

Answer 4

Swaging

Question 5

All are true of a muffler except…

Answer 5

Can be installed only on intake of compressor

Question 6

What device prevents slugging in a heat pump system?

Answer 6

Accumulator

Question 7

Type of circuit where components are arranged in ladder like arrangement?

Answer 7

Parallel circuit

Question 8

A starter relay drops which of the following out of the circuit?

Answer 8

Start windings

Question 9

Thermal device that opens its contacts when motor heater coil uses too much voltage is called a _____________ _________.

Answer 9

Thermal relay

Question 10

How do cooling towers cool?

Answer 10

By evaporation

Question 11

What color is a dot in a moisture site gage system when indicating a dry system?

Answer 11

Green

Question 12

A suction line riser should have a trap installed at the lowest point to….

Answer 12

provide reservoir for oil that drips down riser

Question 13

A yellow tip flame indicates a lack of primary ______ when burning fuel gases in a furnace

Answer 13

primary air

Question 14

What determines defrost termination on a heat pump system using time initiated, temperature terminated defrost cycle?

Answer 14

Outdoor coil

Question 15

What does white smoke from an oil burner indicate?

Answer 15

Lein oil and air mixture

Question 16

Highest temperature at which substance may be liquefied regardless of pressure?

Answer 16

Critical temperature

Question 17

What rating measures furnace efficiency?

Answer 17

AFUE

Question 18

What is the purpose of a condenser?

Answer 18

Cools refrigerant to desired temperature

Question 19

From the expansion valve, the external equalizer runs to…

Answer 19

The outlet of the evaporator

Question 20

Raising superheat will ____________ an evaporator?

Answer 20

Starve

Question 21

A device without moving parts that converts ac voltage to a different voltage is called a _________________.

Answer 21

Transformer

Question 22

Control for refrigeration unit is set to cut in at 45 degrees and out at 35 degrees. If the setting is changed to 45 degrees cut in and 36 degrees cut out, the compressor will have to… (Run less and cycle more or OR run more and cycle less?)

Answer 22

Run less and cycle more

Question 23

A tech finds discharge pressure on a fully charged system is low due to low ambient temperature. How do you resolve this?

Answer 23

Install low ambient fan control

Question 24

The pressure in a system is 32.5 PSIA, what is the gauge pressure? (17.8, 32.5, 47.2 or 61.9)

Answer 24

17.8

Question 25

A manual switch bears markings "1" and "0". What does this indicate?

Answer 25

On/Off

Question 26

What is a type of condensing temperature control?

Answer 26

Fan cycling switch

Question 27

Oil from a hermetic compressor is tested and found to contain acid. This means the compressor has ________________ motor windings.

Answer 27

deteriorating motor windings

Question 28

What controls refrigerant migration in a single compressor, multiple evaporator system?

Answer 28

Check valve

Question 29

What is the unit of current or rate of flow of electricity?

Answer 29

Amps

Question 30

Instrument used to measure relative humidity by comparing wet bulb to dry bulb is called a...

Answer 30

Psychrometer

Question 31

What is required when multiple A/C condensing units are installed outside and evaporators are installed at a different location in building.

Answer 31

Evaporators must be marked and individually identified

Question 32

If required, a refrigerant relief vent is usually located at the ________ ______________.

Answer 32

liquid receiver

Question 33

Pressure gauge of r22 system reads 248 psig and actual line temperature is 100 degrees. What is the amount of subcooling? (12, 14, 16, 18 degrees)

Answer 33

16 degrees

Question 34

What component of a high efficiency gas furnace is not found on a mid-efficiency furnace?

Answer 34

Secondary heat exchanger

Question 35

What kind of circuit has infinite resistance and no current? (Open, Closed, Shorted, Grounded)

Answer 35

Open

Question 36

How many BTU is required to heat 20 lbs of water from 45 degrees to 85 degrees?

Answer 36

800 BTUs page 45

Question 37

The low side of a refrigeration system is characterized by (Evaporator, Suction line, Accumulator)

Answer 37

Suction Line Page 132

Question 38

Condensers remove heat from the refrigerant that it picked up in the evaporator. True or False

Answer 38

True

Question 39

What controls an automatic expansion valve?

Answer 39

Evaporator pressure

Question 40

What is the purpose of an evaporator pressure regulator?

Answer 40

To keep the evaporator pressure above a predetermined point.

Question 41

The capacity of a TEV varies according to all of the following except which of the following: (orifice, pressure differential between high and low side, temperature and condition of the refrigerant in the liquid line, external equalizer)

Answer 41

External equalizer

Question 42

What electrical device converts alternating current to direct current?

Answer 42

Rectifier

Question 43

How do you measure alternating current of a circuit with a meter?

Answer 43

Connect the meter in series

Question 44

What is the latent heat load in BTU/h of air at 1,500 CFM and the absolute humidity difference is 28 grams?

Answer 44

28,560 BTU/h Formula is (0.68 x cfm x grains per pound of dry air)

Question 45

Sensible heat is a measurement of ____ bulb.

Answer 45

dry bulb

Question 46

What is the possible cause of a yellow flame?

Answer 46

Lack of primary air

Question 47

Where is the oil pressure safety cutout located?

Answer 47

Connected to the oil pump at low pressure side

Question 48

In an HVACr system's refrigerant drier, a substance that collects and holds moisture is called a ___________. In dehumidification, a hygroscopic substance that absorbs moisture from the air.

Answer 48

Dessicant

Question 49

The transfer of heat from one place to another by means of a liquid to a gas is __________.

Answer 49

Convection

Question 50

The flow of heat between substances by molecular vibration is called ________________.

Answer 50

Conduction

Question 51

The specific heat capacity for air is ___._____ BTU/Lb F

Answer 51

0.24 BTU/Lb F