Hvac Vocabulary

Question 1

A fast acting fuse is commonly used on motor with a high starting current.

Answer 1

False

Question 2

A flat bimetal strip deforms or bends as temperatures rises because the copper expands more than the steel.

Answer 2

True

Question 3

After a ptc relay increase its resistance, the motor current seeks the path of least resistance, which is through the run capacitor.

Answer 3

True

Question 4

A low pressure safety control is set to maintain a specific evaporator temperature

Answer 4

False

Question 5

A low pressure safety control is set to shut down the compressor in the event of refrigerant loss

Answer 5

True

Question 6

An above atmospheric pressure element is used to control heating units

Answer 6

False

Question 7

An internal bimetal protection device will open the motor circuit when the temperature reaches 200 f to 250 f

Answer 7

True

Question 8

An oil pressure motor control connected to a compressor’s lubrication system shuts off the compressor if the oil pressure drops to low side pressure

Answer 8

True

Question 9

Any standard relay may be used to replace a lockout relay.

Answer 9

False

Question 10

A picture relay has a low resistance when motor circuit is first energize, so it is easier for the current to pass through the PTC relay than through the run capacitor.

Answer 10

True

Question 11

A time delay fuse may allow a motor to be damaged from high current before the time delay is over.

Answer 11

True

Question 12

Bimetal discs are often used for last snap-action applications.

Answer 12

True

Question 13

Current limiting fuses use temperature sensitive resistors that close the motor circuit as temperature rises.

Answer 13

False

Question 14

External bimetal protection devices only open a motor circuit if the current is too high.

Answer 14

True

Question 15

If a thermistor resistance increases as temperature increases, the thermistor has a negative temperature coefficient (NTC).

Answer 15

False

Question 16

If the contact points of a thermostatic motor control were to open very slowly, electric arcing could burn the contacts.

Answer 16

True

Question 17

In order for a PTC relay’s resistance to drop low enough for a motor to start again, it must have enough time to cool down.

Answer 17

True

Question 18

The fuses for a motor in an HVACR system are usually factory installed within the compressor dome.

Answer 18

False

Question 19

The vertical lines in a ladder diagram identify the controls and loads located in a circuit.

Answer 19

False

Question 20

Three phase motors may use the same starting relays that single phase motor use.

Answer 20

False

Question 21

When the pressure inside an above atmospheric pressure elements increase, it closes a electrical circuit.

Answer 21

True

Question 22

When the thermistor in a PTC relay has high resistance, it acts as a close switch or contact.

Answer 22

False

Question 23

Copper conducts heat better than glass.

Answer 23

True

Question 24

During a state change, the temperature of the substance always change.

Answer 24

False

Question 25

The sun heats the earth through conduction

Answer 25

False

Question 26

During operation, the compressor motor will rotate in the opposite direction to change the direction of refrigerant flow.

Answer 26

False

Question 27

In a split phase motor, the run winding has the greatest amount of resistance.

Answer 27

False

Question 28

The contacts of a potential relay are normally open.

Answer 28

False

Question 29

A shade pole motor has a high starting torque

Answer 29

False

Question 30

The human body has resistance.

Answer 30

True

Question 31

The starting winding is wound with finer wire than the running winding so it has great resistance.

Answer 31

True

Question 32

The start capacitor is connected in series with the starting winding.

Answer 32

True

Question 33

The voltage draw is more when the motor is starting than when it is running.

Answer 33

True

Question 34

Most thermostat in the HVAC industry are 120 volts.

Answer 34

False

Question 35

Digital thermostats usually display temperature, time of day, programming and operating status.

Answer 35

True

Question 36

Single phase motor are more efficient than three phase motor.

Answer 36

False

Question 37

If contact become dirty or pitted, it is acceptable to sand or file them as a permanent repair.

Answer 37

False

Question 38

When testing a motor with a ohmmeter, one winding show a 1000 ohm continuity to motor frame. This is an indication of a good safety ground.

Answer 38

False

Question 39

A 240 volt, 3 wire circuit can be split into two 120 volt circuits.

Answer 39

True