Hvac journeyman test

Card Set Information

Hvac journeyman test
2013-04-04 16:51:38
Hvac journeyman test

Hvac jurneyman test
Show Answers:

  1. sensible heat is described as
    heat that can be measured
  2. specific heat is defined as
    the amount of heat required to raise one pound of a substance one degree Fahrenheit
  3. Latent heat is defined as
    heat used to cause a change of state
  4. a BTU is
    the amount of heat required to raise one pound of water 1 degree Fahrenheit
  5. 1 ton of refrigeration is
    2000× 144× 24, 288, 000 BTU/24 hours, and 12,000 BTU/hr
  6. a room thermostat should be mounted
    five feet from the floor
  7. to provide proper oil return to the compressor
    the suction line must be pitch towards the compressor
  8. what is the purpose of the external equalizer on a TXV
    to offset for the pressure drop across the evaporator
  9. what would be the minimum bending radius on one inch soft copper tubing
    5 inches
  10. what is the heating value of natural gas
    1000 BTU/cu ft
  11. the purpose of a fan control is too
    start and stop the fan motor
  12. a limit control
    d energizes the gas firing circuit upon high bonnet temperatures
  13. an unconfined space is
    a space who's volume is greater than 50 cu ft /1000 BTU/h  of total input of all gas fired appliances
  14. what is the total free area of a 15"× 24"combustion air opening used with the metal grill with an unknown free area
    270 sq in
  15. a confined space is
    a space whose volume is less than 50 cu ft/ 1000 BTU/ h of total input of all gas fired appliances
  16. what is the purpose of the reversing valve on the air to air heat pump
    it changes the flow of the refrigerant making the indoor coil the outdoor coil on the Outdoor Coil the indoor coil
  17. which of the following is connected to the top port of a reversing valve
    the discharge line in the compressor
  18. 1 horsepower is the same as
    746 watts
  19. 1 watt equals
    3412 BTU
  20. and open run winding will be indicated by which of the following using an ohm meter
    infinite ohms from run to start
  21. a grounded condition found with an ohm meter on a compressor motor will be indicated by which of the following
    A zero reading from any terminal to compressor housing
  22. the heat anticipator
    is wired in series with the operating contact
  23. a cooling anticipator
    is wired in parallel with the operating contacts
  24. what is the purpose of the solenoid valve
    it controls the flow of a fluid
  25. which of the following is used in a heat pump to change the indoor coil to the outdoors
    a reversing valve solenoid
  26. which of the following is the correct method for fastening sheet metal joints
    steel metal screws
  27. the adding of heat to a refrigerant that has reached its vapor saturation point is referred to as
    superheating the refrigerant
  28. the specific heat of air is
    .24 BTU/lbº Fahrenheit
  29. Enthelapy is
    the measure of the heat content of a substance
  30. which of the following is permitted to be used pressure checking a refrigeration system
  31. using Ohm's law what would R= if e=120 and I=40
  32. a circuit having a voltage of 120 volts applied and is drawing two amps would have a resistance of
    12 ohms
  33. which of the following is false about transformers
    a step down transformer produces more voltage on the secondary winding than the voltage applied to the primary
  34. a positive temperature coefficient PTC device is used for which of the following purposes
    start assist for PSC motor
  35. a 24 volt transformer with a rating of 60va has maximum current carring output of
  36. a rectifier is used to
    change AC voltage to DC voltage
  37. a thermistor may be used for which of the following
    to provide temperature readout to assist in the starting of a PSC motor and to stop a motor on an overload condition
  38. which of the following is true about an internal motor temperature cut out
    opens the circuit on temperature rise and stops the motor
  39. which of the following is adjustable on a thermostat
    the bi metal strip
  40. which of the following is a cause of hermedic compressor motor overheating and cutting out on the internal overload device
    refrigerant  under charge
  41. the point or pressure setting at which a pressure sensing device interrupt the electrical circuit is known as the
    cut out
  42. which of the following is not a type of a fan switch used on a gas furnace
    temperature on - time off
  43. which of the following is required when the thermostat subbase designed for two 24 volt power sources is used with one power source
    hey jump wire is required to be connected between RH and RC terminal
  44. which of the following is false about the use of direct digital controls
    it is a manual control system that requires more maintenance
  45. the number of poles in a single phase motor determines the
  46. and open circuited run capacitor has which of the following affects on a motor
    running amperage will be high motor may fail to start and motor will get hot if operation at full load
  47. how does the run capacitor affect the operation of a capacitor start capacitor Run compressor motor
    limits the current through the start winding so the wind ing will not get hot
  48. which of the following is used in a permanent split capacitor motor
    run capacitor
  49. which of the following Motors has the lowest starting torque
    permanent split capacitor
  50. 2 ohms--------A--------------9 ohms       
                 |                                                   |
         B--------------7 ohms------------C
    refer to the diagram above in on meter indicates the reading shown on the diagram when checking motor winding which of the following is true about the reading
    B is common-A is run- C is start
  51. when identifying common, start and run terminals of an unfamiliar compressor motor, the following resistance reading are measured across the terminals
    terminal A to Terminal B =7 ohms
    terminal A to Terminal C =2 ohm
    terminal B to Terminal c= 2 ohms
    which of the following is the correct terminal designation B is common, A is start, C is run
  52. the potential relay used on a CSCR motor removes which of the following from the motor circuit
    start capacitor
  53. the contacts of a potential relay are between terminals
    one and two
  54. which of the following is not used on a median for cooling electric motors
    refrigerant liquid
  55. the "NO" (normally open)contacts. of a fan relay used on a combination heating and air conditioning system connects to the
    common motor tap
  56. lowering the voltage applied to a motor that is running will cause the current draw of the motor to
  57. which of the following changes may be used to reduce the speed of an open compressor driven by belt type motor
    change the drive pulley to a smaller diameter
  58. which of the following is a precaution used in replacing belt on a belt driven compressor
    A marked match set of belts shall be used when replacing one or more
  59. a single contact contactor is used in some cases too
    provide crankcase heat to the compressor
  60. all by metal overload devices are designed with snap action to avoid excessive
    arcing of the contacts
  61. which of the following is a factor in determining why an electric motor hums and then shuts off
    mechanical problem, load problem, electrical problem
  62. the boiling temperature of the liquid refrigerant determines the
    evaporator coil operating temperatures
  63. the difference between the boiling refrigerant temperature and the evaporator outlet temperature is known as
  64. which of the following is the function of a normal condenser
    de superheat the refrigerant, condense the refrigerant ,subcool the refrigerant
  65. which of the following is true about a vapor charge both used on a thermostatic expansion valve
    the valve body is required to be kept warmer than the bulb
  66. which of the following metering devices controls refrigerant flow by pressure drop
    capillary tube
  67. which of the following is true about capillary tube metering devices they control
    refrigerant flow by pressure drop
  68. what is the purpose in using a low ambient control
    to keep the head pressure up to an acceptable level
  69. the oil pressure control needs a differential in pressure to allow power to pass to the compressor therefore it must have some means to allow the compressor to get started which of the following is used to accomplish this
    a time delay is built into the control
  70. the heat anticipator used in a thermostat with electric heat may be sent by
    adding all current draw in the 24 volt heating circuit that passes through the heat anticipator
  71. which of the following functions may not be incorporated in a low voltage electric heat sequencer
    energize the transformer control circuit
  72. an electric furnace is being replaced with gas fired appliance the electric furnace has an amp draw of 50 amp at 208 volts and a 40 degree temperature rise which of the following furnaces would be required
    35496 btuh output (50×208×3413=35495)
  73. at 70,000 BTuh electric resistance heat furnace has a temperature rise of 50 degree Fahrenheit how many cubic feet per minute of air is required across the electric heating elements of the furnace
    3332 ( 70000 ÷ by 1.0505 ×50=3332
  74. when burned with air 1 cubic foot of natural gas will produce about how many BTU's of heat energy
  75. A gas furnace has an input rating of 100,000 btuh and a temperature rise of 50 degrees Fahrenheit how much air is moving across the exchanger in CFM's
  76. and expansion valve uses an external equalizer to
    compensate for excessive pressure drop across an evaporator coil
  77. excessive platinum Plenum (bonnet) temperature in Furnace are prevented by which of the following devices
    limit switch
  78. a pilot is not used with which of the following burner ignition devices
    spark to burner