TPC 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 refrigeration 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 compressors, the crankshaft is usually vertical in a(n) _______ compressor, but horizontal in a(n) ________ compressor.

Answer 6

Full-hermetic; open

Question 7

On the pistons of reciprocating compressors, the ________ ring(s) prevent oil from reaching the compression chamber. The _______ ring(s) 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 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 impeller’s _______ 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 compressor’s capacity by closing pre-rotation vanes raises the pressure in the system’s ______.

Answer 20

Evaporator

Question 21

Which of the following is an important factor to consider when selecting a motor to run 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 240 V instead of 120 V, you need to:

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 to prevent:

Answer 27

Voltage drops to other equipment

Question 28

Overload protection for compressor motors may be provided by a(n):

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 compressors and related components is to:

Answer 31

Follow the manufacturer's recommended maintenance schedules and procedures

Question 32

Typical preventative maintenance procedures for compressors and related equipment include:

Answer 32

Listening for unusual noises

Question 33

A compressor may overheat because of a(n):

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