Local 290 HVAC Term 6

  1. Define Refrigeration:
    Refrigeration is cooling by the removal of heat
  2. Heat is a form of __
  3. As the temperature of any substance increases, the molecules which make it up vibrate:
  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:
    Fahrenheit and Centigrade
  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?
  9. T or F:
    A sensible heat change always causes a change in temperature?
  10. T or F:
    A latent heat change always causes a change in molecular activity?
  11. T or F:
    A thermometer can be used to measure latent heat change?
  12. T or F:
    There is a change of state in a substance whenever latent heat is added to it or removed from it?
  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 ___
  19. In terms of refrigeration language, the water we drink is:
  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
  23. 48,000 Btuh=___tons
  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 ___
  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 ___
  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:
  35. The device used in circuits to prevent damage from overloads is called a:
  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?
  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?
  46. Most common control circuits operate from ___ volts AC
  47. High voltages, such as 120v or 240v household supplies, are always dangerous. Under certain conditions, however, even low ___ can be lethal
  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?
  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?
  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?
  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?
  58. T or F:
    Heat flows from cold to warm?
  59. T or F:
    Sensible heat can measured with a thermometer?
  60. Most of the heat transfer in a mechanical refrigeration system takes place because the ___ changes state.
  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?
  63. T or F:
    The solenoid coil is considered an electrical load in the circuit?
  64. In a circuit with two solenoids the correct wiring method would be to wire in a series or parallel circuit?
  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?
  67. T or F:
    Head pressure is read at the evaporator?
  68. T or F:
    Capillary tubes are used as metering devices
  69. T or F:
    Thermostatic expansion valves automatically adjust flow of refrigerant according to the superheat sensed?
Card Set
Local 290 HVAC Term 6
Info that will be on the test