433

Question 1

A positive displacement compressor uses a piston or other device to

Answer 1

compress refrigerant vapor in a chamber

Question 2

which of the following is a kind of kinetic displacement compressor

Answer 2

centrifugal

Question 3

which of the following is part of a scroll compressor

Answer 3

swing link

Question 4

a multiple stage refrigerant system has more than one

Answer 4

compressor

Question 5

when selecting a replacement compressor you need to make sure the replacement will operate with/at the proper

Answer 5

discharge pressure

Question 6

among reciprocating compressor the crankshaft is usually vertical in a ___ compressor but horizontal in a ___ compressor

Answer 6

full hermetic; open

Question 7

on the pistons of reciprocating compressors, the ___ rings prevent oil from reaching the compression chamber. The ___ ring prevent refrigerant from escaping around the piston during compression

Answer 7

bottom; top

Question 8

which of the following is a method of distributing lubricating oil in a reciprocating compressor

Answer 8

crankshaft splash

Question 9

a cylinder unloader reduces the capacity of a reciprocating compressor by allowing refrigerant to flow through the ___ port during the ___ stroke

Answer 9

suction; compression

Question 10

one way of reducing vibration problems in a reciprocating compressors involves the use of

Answer 10

spring mounts

Question 11

one advantage of rotary compressors over reciprocating compressors is that the

Answer 11

vibration is less

Question 12

slugging is the entry of ___ refrigerant into a compressor. Cavitation is the formation and collapse of ____ in a liquid flowing under pressure

Answer 12

liquid; vapor pockets

Question 13

one purpose of the accumulator on a rotary compressor is to

Answer 13

keep dirt and debris out of the compressor

Question 14

helical compressors differ from rotary compressors in that they have

Answer 14

no vanes

Question 15

in a scroll compressor one scroll is stationary and the other ___ refrigerant enters the scrolls at the __ and leaves at the center

Answer 15

orbits; outer edge

Question 16

the amount of compression in a centrifugal compressor depends on the ___ the impeller, which depends in turn on the impellers ___ and rate of rotation

Answer 16

tip speed of; diameter

Question 17

in reverse hydrostatic sealing the flow of ___ across the seal opposes the flow of ____ across the bearing

Answer 17

refrigerant vapor; oil

Question 18

in multistage centrifugal compressors thrust loads are reduced by

Answer 18

opposing impellers

Question 19

the purpose of a purge system on a condenser is to eliminate ___ from the refrigeration system

Answer 19

air

Question 20

reducing a compressors capacity by closing pre rotation vanes raises the pressure in the systems ___

Answer 20

evaporator

Question 21

which of the following is an important factor to consider when selecting a motor to tun a refrigeration compressor

Answer 21

horsepower rating

Question 22

which of the following motors can be used in hermetic compressors

Answer 22

capacitor start, induction run

Question 23

you can reverse the direction of a single phase induction motor by

Answer 23

reversing the connection of either the starting or running winding

Question 24

to change a dual voltage motor to run on 240v instead of 120v you need tp

Answer 24

connect the two running windings in series

Question 25

a single phase motor used in a hermetic compressor has a relay to disconnect the starting winding from the circuit when the motor approaches its running speed. One kind of relay operates when the current in the ___ winding falls to a preset value. Another kind operates when the voltage across the ___ winding rises to a preset value

Answer 25

running; starting

Question 26

the two basic categories of motor starting devices are

Answer 26

contactors and starters

Question 27

a reduced voltage starter limits the current to the motor at startup in order top prevent

Answer 27

voltage drops to other equipment

Question 28

overload protection for compressor motors may be provided by a

Answer 28

external bimetallic disk

Question 29

crankcase heaters are especially useful on compressors that are subjected to

Answer 29

cold climates

Question 30

installing a suction line accumulator can protect a compressor from damage caused by

Answer 30

slugging

Question 31

the first rule of preventative maintenance for all compressors and related components is to

Answer 31

follow the manufacturers recommended maintenance schedules and procedures

Question 32

typical preventative maintenance procedures from compressors are related equipment include

Answer 32

listening for unusual sounds

Question 33

a compressor may overheat because of a

Answer 33

low oil level

Question 34

when pumping down a compressor for service run the compressor with the valve on the suction line closed then close the valve on the discharge line and stop the compressor. Repeat this process until the pressure holds at ___ psig

Answer 34

+2 to +5

Question 35

After disassembling a reciprocating compressor and cleaning the parts you should inspect the parts for

Answer 35

excessive wear on bearing surfaces