Unit 23 Quiz

Question 1

If the compression ratio of a reciprocating compressor increases, the amount of refrigerant pumped by the compressor ________.

Answer 1

Will decrease

Question 2

What component connects the piston to the crankshaft in a reciprocating compressor?

Answer 2

Connecting rod

Question 3

Flank sealing takes place in a ______ compressor.

Answer 3

Scroll

Question 4

The hermetic compressor shell is typically thought of as a _______ component.

Answer 4

Low side

Question 5

Two-stage compression is not generally used until the compression ratio exceeds 10:1, often experienced with __________.

Answer 5

Low temperature refrigeration

Question 6

What is the function of the compressor in a refrigeration system?

Answer 6

It is a vapor pump that converts low pressure low temperature vapor into high pressure high temperature vapor

Question 7

Compute the compression ratio using 14.7 psi as the conversion factor when the suction pressure is -3.1 psig and the discharge pressure is 198.9 psig for a low temp system using R-404A.

Answer 7

Question 8

True or false: A semi-hermetic compressor can be taken apart and serviced.

Answer 8

True

Question 9

True or false: The screw compressor uses an open motor instead of the hermetic design.

Answer 9

True

Question 10

True or false: Motors for hermetic compressors are manufactured with the same materials as standard electric motors that operate in an open-air environment.

Answer 10

False

Question 11

True or false: The rotary screw compressor is another name for the rotary type compressor.

Answer 11

False

Question 12

True or false: To keep refrigerant vapor from leaking over the top of the scrolls, tip seals are used.

Answer 12

True

Question 13

True or false: The centrifugal compressor is a positive displacement type compressor.

Answer 13

False

Question 14

True or false: High compression ratios above 12:1 are not recommended by most manufacturers.

Answer 14

True

Question 15

True or false: Open drive compressors are manufactured in two styles, belt driven or gear driven.

Answer 15

False

Question 16

True or false: The discus valve in a reciprocating compressor has a smaller clearance volume than reed/flapper valves.

Answer 16

True

Question 17

True or false: The scroll compressor takes a fixed volume of gas at a suction pressure and then maintains the same gas volume to increase its pressure.

Answer 17

False

Question 18

True or false: A two-step scroll compressor uses motor speed to control cooling capacity.

Answer 18

False

Question 19

List four causes that may lead to liquid refrigerant entering the compressor.

Answer 19

Broken evap fan,
broken metering,
dirty air filter,
overcharging

Question 20

Where would you check an open drive compressor for a possible refrigerant leak?

Answer 20

Shaft seal

Question 21

An electric motor is connected to an open compressor that is rated for 50 tons using R-22 refrigerant. The drive pulley is 5 inches in diameter and spins at 3600 rpm. The compressor needs to run at 1750 rpm. What is the diameter of the pulley on the compressor?
(drive pulley size x drive pulley rpm = driven pulley size x driven pulley rpm)

Answer 21

Question 22

A disengaging solenoid valve is used to vary cooling capacity in a scroll compressor. What is the external feature that distinguishes a digital capacity scroll compressor from a two-step capacity scroll compressor?

Answer 22

Solenoid valve, outside compressor

Question 23

Used to suppress compressor pulsating noises.

Answer 23

Muffler

Question 24

Holds the suction and discharge valves.

Answer 24

Valve plate

Question 25

Belt or direct drive. Must have a shaft seal to keep refrigerant from escaping.

Answer 25

Open compressor

Question 26

Determines the direction the gas entering the compressor will flow.

Answer 26

Refrigerant cylinder valves

Question 27

What external feature on the exterior of a compressor identifies it as a two-stage compressor that will utilize the Y2 terminal in the thermostat?

Answer 27

Two electrical connectors on each side

Question 28

Which compressor doesn’t have a clearance volume and is more efficient than a reciprocating compressor?

Answer 28

Screw, rotary, centrifugal

Question 29

Why is it bad to start a hermetic compressor when it is in vacuum? Explain in detail.

Answer 29

Starting a hermetic compressor while in vacuum may cause an explosion due to Terminal Venting

Question 30

Which type of v-belt is better at dissipating heat when used around small pulleys?

Answer 30

Cog belt

Question 31

A 3-phase internal thermal overload will disconnect all three of the overload contacts at the same time if a motor overheating problem occurs. What happens if only one of the overload contacts opens?

Answer 31

Two of contacts will remain in circuit, resulting in overheating and high current draw