# Local 290 HVAC Term 6

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1. Define Refrigeration:
Refrigeration is cooling by the removal of heat
2. Heat is a form of __
energy
3. As the temperature of any substance increases, the molecules which make it up vibrate:
Faster
4. One pound of refrigerant will take up the most space:
As a gas because it has the lowest density
5. Name the two most commonly used scales to measure temperature:
6. A cooling coil has 40 degree refrigerant inside its tubes while 80 degree air passes over it. Because heat flows "downhill", it will move from:
The coil surface into the air
7. The three ways heat is transferred are called ___, ___, ___
Conduction, convection, and radiation
8. Which one of these is a good insulator and, therefore a poor conductor?
Polystyrene
9. T or F:
A sensible heat change always causes a change in temperature?
True
10. T or F:
A latent heat change always causes a change in molecular activity?
True
11. T or F:
A thermometer can be used to measure latent heat change?
False
12. T or F:
There is a change of state in a substance whenever latent heat is added to it or removed from it?
True
13. Total Heat=
Sensible Heat + Latent Heat
14. Temperature cannot measure total heat because:
It cannot measure latent heat, which is part of total heat
15. BTU stands for ___ ___ ___
British Thermal Unit
16. A BTU is the amount of heat required to raise 1 pound of ___ ___F.
water 1 degree
17. Define Specific Heat:
It is the amount of heat required to raise 1 pound of a substance 1 degree Fahrenheit.
18. The total heat (in BTU) which a pound of any substance contains is called its ___
Enthalpy
19. In terms of refrigeration language, the water we drink is:
Subcooled
20. The amount of heat transfer and rate of heat transfer are different because:
Amount deals with "how much" while rate deals with "how fast"
21. 1 ton of refrigeration capacity or cooling load is:
12,000 Btuh
22. 3 1/2 tons= ___Btuh
42,000
23. 48,000 Btuh=___tons
4
24. Define Pressure:
Its force per unit of area
25. Which of the following expresses pressure?
Pounds per square inch
26. Pressure in an operating refrigeration system is most often measured in ___
psig
27. Pressure is measure in ___ when evacuating a system before it is charged with Freon.
In., Hg., Vac.
28. What will the gauge pressure reading be for:

14.7 psia ___
0 psig
29. What will the gauge pressure reading be for:

Standard atmospheric pressure ___
14.7 psig
30. What will the gauge pressure reading be for:

54.7 PSIA ___
40 psig
31. As pressure rises saturation temperature ___
rises
32. A body has a negative charge when it:
Contains an excess or electrons
33. The force acting between two bodies dis-similarly charged:
is referred to as an electrostatic field
34. In electrical circuits, the time of doing work is expressed in:
Watts
35. The device used in circuits to prevent damage from overloads is called a:
Fuse
36. If the resistance is held constant, what happens to power if the current is doubled?
Power is multiplied by 4
37. Soft iron is most suitable for use in a:
temporary magnet
38. Around a magnet, the external lines of force:
leave the magnet from the north pole and enter the south pole
39. When a conductor moves across a magnetic field:
A voltage is induced in the conductor
40. When voltage is applied to a conductor, free electrons:
Are impelled along the conductor
41. Which of the following is considered to be the best conductor?
Silver
42. Electrically operated devices in gas burning equipment use the electricity producing principle of:
Dissimilar metals heated
43. If a circuit is constructed so as to allow the electrons to follow only one possible path, the circuit is called a(n):
Series circuit
44. In a series circuit, the total current is:
the same through all parts of the circuit
45. T or F:
Primary load devices are located in the line voltage circuit?
True
46. Most common control circuits operate from ___ volts AC
24
47. High voltages, such as 120v or 240v household supplies, are always dangerous. Under certain conditions, however, even low ___ can be lethal
voltages
48. What items listed below are considered load devices?
Compressor, indoor fan motor, outdoor fan motor
49. T or F:
The indoor fan motor is located in the low voltage circuit?
False
50. Thermal overload devices respond to the heat generated by ___ flow.
excessive current
51. T or F:
The low pressure and high pressure switch are normally in series with the compressor contactor?
True
52. OFM is abbreviated for ___
Outdoor fan motor
53. IFM is abbreviated for ___
Indoor fan motor
54. On a loss of refrigerant the low pressure switch closes or opens to de-energize the compressor circuit?
Opens
55. As the warm air from the room passes over the evaporator what happens to the refrigerant temperature?
It rises
56. As superheat at the evaporator outlet increases, what does the metering device do in response?
It opens
57. T or F:
Heat is transferred from the indoor air to the outdoor air by the refrigerant?
True
58. T or F:
Heat flows from cold to warm?
False
59. T or F:
Sensible heat can measured with a thermometer?
True
60. Most of the heat transfer in a mechanical refrigeration system takes place because the ___ changes state.
refrigerant
61. On an air cooled condenser the fan motor fails, which switch will protect the compressor?
High Pressure Switch
62. T or F:
The solenoid uses magnetism to open the valve?
True
63. T or F:
The solenoid coil is considered an electrical load in the circuit?
True
64. In a circuit with two solenoids the correct wiring method would be to wire in a series or parallel circuit?
Parallel
65. The ___ valve regulates and controls the supply ___ to the burners.
gas, gas
66. T or F:
A metering device at the evaporator maintains sub-cooling of the refrigerant?
False
67. T or F:
Head pressure is read at the evaporator?
False
68. T or F:
Capillary tubes are used as metering devices
True
69. T or F:
Thermostatic expansion valves automatically adjust flow of refrigerant according to the superheat sensed?
True

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 Author: TWilson88 ID: 292865 Filename: Local 290 HVAC Term 6 Updated: 2015-01-13 05:19:13 Tags: HVAC Folders: Description: Info that will be on the test Show Answers:

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