Question and answer

Question 1

#70
most compressors are positive displacement machines name a compressor that is not a positive displacement machine

Answer 1

D

Centrifical

Question 2

#71
The ratio of the actual volume of refrigerant Vapor pumps to the theoretical displacement volume is known as

Answer 2

A

Volumetric efficiency

Question 3

#72
 air compressor in which the compressor and motor are both sealed within the same pressurizing housing is known as a

Answer 3

C

Hermetic compressor

Question 4

#73
 the passage of liquid refrigerant through the compressor suction and discharge valve should be avoided and is known as

Answer 4

B

Slugging the compressor

Question 5

#74
 modern high speed reciprocating compressors typically

Answer 5

D a+b
A= 1750 RPMs partially correct there is another common speed also
B= 3450 RPM partially correct there is another common speed as well the 1750

Question 6

#75
Compressor capacity decreases as

Answer 6

D all above

discharge pressure increases suction pressure decreases compressor speed decreases

Question 7

#76
 an advantage of the

Answer 7

D all above

smooth quiet operation low torque variation through overlapping compression Cycles you moving parts

Question 8

#77
 how can you identify reverse

Answer 8

D a+b

the compressor will not compress the compressor will Stop on motor overload

Question 9

#78
 during scroll compression

Answer 9

A

refrigerant Vapor enters from the outside of the scroll and exits at the center

Question 10

#79
 capacity control on a helical rotary compressor is obtained using(screw type)

Answer 10

D

a sliding valve

Question 11

#80
 the screw type impellers used in a helical rotary compressors are also known as

Answer 11

A

Rotors

Question 12

#81
 the component in a centrifugal compressor that actually does the compressing is known as

Answer 12

A

An impeller

Question 13

#82
 a centrifugal compressor controls capacity through the use of

Answer 13

D a+c

variable speed and Vortex dampers

Question 14

#83
 bearings in a centrifugal compressor can be checked by

Answer 14

C

checking the temperature of the oil returning from the bearing

Question 15

#84
 a small access valve which is similar to the air valve used on tires is known as

Answer 15

B

Schrader valve

Question 16

#85
 a valve used to prevent flow of liquid refrigerant to the evaporator and to avoid flood back to the compressor during off Cycles is the

Answer 16

D

Solenoid valve

Question 17

#86
 a special value used to prevent evaporator temperature from falling below a predetermined minimum temperature regardless of suction pressure is the

Answer 17

A

Evaporator pressure regulator

Question 18

#87
 a metering device with the characteristic of feeding liquid into the evaporator at the same rate at the liquid flows from the condenser is the

Answer 18

B
high side float valve this valve consists of a float in a needle valve which creates the pressure drop separating the high side from the low side of the system as a liquid level from the condenser raises the flow Rises and opens needle valve forcing refrigerant into the evaporator . As the liquid level from the condenser drops the float drops also and closes the needle valve restricting the flow to the evaporator

Question 19

#88
 in a thermostatic expansion valve three forces act on the diaphragm in the powerhead which is connected to the valve evaporator pressure acts too .......,  the spring pressure acts too .......... and the bulb pressure attached to the evaporator Outlet, acts to ....... the valve

Answer 19

B

close close open

Question 20

#89
 metering device that actually measures temperature rather than pressure or liquid levels is the

Answer 20

D

Thermal electric valve

Question 21

#90
 suction Line Filter drier should be installed whenever

Answer 21

C

a hermetic compressor motor burnout has occurred

Question 22

91

filter dryers, and dryers
are filled with a material that is able to catch and retain moisture and acid This material is called?

Answer 22

B

Desiccant

Question 23

92

suction Line Filter driers are usually equipped with Gauge connections so that pressure drops can be determined.
Why?

Answer 23

D

so that you can determine when to change the filter drier.

Question 24

93

in general the greater the number of rows in an evaporator……………
.
……………………………..

Answer 24

D all above
the more closely the leaving air temperature will be to that of the refrigerant the, the more dehumidification
can take place, The colder the leaving air will be. To

Question 25

#94
 increasing airflow over an evaporator

Answer 25

A

increases evaporator capacity

Question 26

#95
 capacity control of a lithium bromide water absorption machine is accomplished

Answer 26

B
by controlling the heat input to the generator,
more heat results in an increased amount of refrigerant boiled out of the solution in the generator,
Creating more Refrigeration effect. Less heat results in less Refrigeration effect

Question 27

#96
 crystallization may occur in a lithium bromide water absorption chiller

Answer 27

D all above
if power fails while the machine is under a heavy load, if condenser water is allowed to get too cold, If the machine over cools during a shutdown period.

Question 28

#97
 the heat source for absorption liquid chillers could be

Answer 28

D all above

solar panels, Steam, hot water.

Question 29

#98
 The Purge units on absorption liquid chillers are designed to

Answer 29

C

expel non-condensable gases

Question 30

#99
 a possible cause for high head pressure is

Answer 30

D all above
dirty condenser tubes cause a reduction in the ability of the condenser to reject heat resulting in higher condensing temperatures and pressure,
insufficient water flow through the condenser reduces the ability of the condenser to reject heat resulting in higher pressure and temperature,
air and non condensables in the condenser

Question 31

#100
 approach temperature is the difference between

Answer 31

A

condensing temperature and leaving water temperature

Question 32

#101
Gpm=btuh/500×TD
TD=total difference

Answer 32

1.5gpm=15000btuh/500×TD(20°f)

Question 33

#103
 what are the products of perfect combustion using oxygen and a hydrocarbon fuel

Answer 33

B

carbon dioxide, heat,water

Question 34

#104
 describe the appearance of a properly adjusted natural gas flame  in an atmospheric burner

Answer 34

C
study blue flame with a smaller lighter blue inner cone, resting on the burner
Port

Question 35

#105
 radiant tubing or piping should be pressure-tested to at least ................times expected operating pressure

Answer 35

B

2 times

Question 36

#106
 when filling a radiant heating system, it is recommended to fill

Answer 36

C

slowly from the low point so that the tendency for air pockets to form is reduced

Question 37

#107
 infrared heaters use burning gas to heat a specific radiant surface instead of using the infrared energy from the Open Flame because

Answer 37

A

heated surfaces are better heat radiators than open flame

Question 38

#108
High efficiency (condensing) 
 furnaces achieve and efficiency of up to 95% by

Answer 38

B

cooling the exhaust gases to below dewpoint and recovering some of the latent heat of condensation