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2nd Year Finals > Lab > Flashcards

Lab Flashcards

1
Q

What is compressor flooding?
What damage does it cause?
How to prevent it?

A

Small amounts of liquid refrigerant in compressor.
Air cooled compressors - wears pistons and causes blow-by
Suction cooled compressors- dilutes oil & decreases lubrication
Prevent: Ensure 20 F Superheat

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2
Q

What is compressor slugging?
What damage does it cause?

A

Large amounts of liquid refrigerant entering compressor.
Broken internal parts.

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3
Q

What is a flooded start in a compressor?
How do you prevent flooded starts?

A

Flooded starts is refrigerant migration in the off cycle to the compressor.
Prevented by crankcase heaters and pumpdown/pump out control modes

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4
Q

What temperature does oil lose it’s lubrication?

A

300 F

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5
Q

What temperature does oil begin to break down?

A

350 F

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6
Q

How far from the discharge port do you measure overheating temperature and what is the maximum allowed temperature at this point?

A

6 Inches from discharge port and no more then 225 F

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7
Q

Current Relays have a NO or NC set of contacts?

A

NO

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8
Q

Potential Relays have a NO or NC set of contacts?

A

NC

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9
Q

Current relays are often used on what type of compressor?

A

Hermetic Compressors

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10
Q

Potential Relays are normally used on what type of compressors?

A

Semi-hermetic Compressors

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11
Q

Potential Relays are in series or parallel with the start winding?

A

Parallel

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12
Q

Current relays are wired in series or parallel with the run winding?

A

Series

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13
Q

Start capacitors must not exceed what % of their rated mfd?

A

130%

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14
Q

What type of contacts does a PTC relay have?

A

No set of contacts

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15
Q

Hot Wire Relays have how many sets of contacts?

A

2

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16
Q

Run Capacitors stay in the circuit, true or false?

A

True

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17
Q

Adding micro farad ratings in a parallel circuit is done by?

A

MFDt=MFD1 + MFD2

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18
Q

Potential Relays Contacts switch on an increase or decrease of voltage?

A

Increase

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19
Q

Adding micro farad ratings in a series circuit is done by

A

1/MFDt = 1/MFD1 + 1/MFD2

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20
Q

What happens to current relays contacts when the compressor hits LRA?

A

The contacts close

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21
Q

Relief valves are sized and rated according to?

A

SCFM or lbs of dry air per minute

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22
Q

According to Ashrae the relief valve settings must be…?

A

25% higher than the maximum expected operating pressure and not higher than the pressure rating of the vessel

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23
Q

Run capacitors can be replaced with what % larger than it’s original size?

A

110%

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24
Q

Start Capacitors help with what?

A

Starting Torque

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25
Q

Start Capacitors stay in the circuit. True or False?

A

False

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26
Q

RSIR has what type of capacitor?

A

No Capacitor

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27
Q

RSIR keeps the start winding in the circuit. True or False?

A

False

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28
Q

RSIR motors are only found alongside fixed orfices and cap tubes?

A

True

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29
Q

CSIR has what kind of capacitor?

A

Start Capacitor

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30
Q

CSIR motors can be used with TXV’s. True or False?

A

True

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31
Q

CSCR has what kind of relay?

A

Potential Relay

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32
Q

In a CSCR motor the caps are in series or parallel?

A

Parallel

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33
Q

PSC stands for what?

A

Permanent Split Capacitor

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34
Q

The start winding does what in a PSC motor?

A

Stays in the circuit

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35
Q

PSC motors have what type of capacitor?

A

Run Capacitor

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36
Q

Line Duty overloads directly or indirectly cut power to the compressor?

A

Directly

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37
Q

Pilot Duty overloads cut power to the compressor how?

A

Indirectly via contactor or relay

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38
Q

Inherent overloads combine which two properties?

A

Heat and current

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39
Q

The write pin connects which two parts of a reciprocating compressor?

A

Piston and the connecting rod

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40
Q

In a Defrost Timeclock, Defrost termination occurs between which two sets of contacts?

A

3 and X

41
Q

In a Defrost Timeclock, the normally open contacts are between which numbered conatcs?

A

1 and 3

42
Q

In a Defrost Timeclock, which two contacts are always jumpered?

A

1 and 2

43
Q

Oil Failure controls are automatic resets. True or False?

A

False

44
Q

OFC use what device to utilize either 120 or 208 supply voltage?

A

Drop Resistor

45
Q

If the capillary lines off of an oil failure control are inadvertently reversed in connections the result would be?

A

The compressor will start and then go off on oil failure

46
Q

Where is the ideal bulb postion on the suction line for pipe 7/8” & larger?

A

4 or 8 o’clock

47
Q

Where should you NOT mount the TXV bulb?

A

6 o’clock

48
Q

What is the purpose of all evaporator feed devices?

A

Reduce the pressure and meter refrigerant into the evaporator

49
Q

What is the opening force of a TXV?

A

Bulb Pressure

50
Q

What is the closing force of a TXV?

A

Evaporator Pressure & Spring Pressure

51
Q

An oversized TXV will do what to the evaporator?

A

Hunt

52
Q

An undersized TXV will do what to the evaporator?

A

Starve

53
Q

You must use an externally equalized TXV with what piping device?

A

Distributor

54
Q

You must use an externally equalized TXV if the pressure decrease the evaporator is greater than what?

A

2 F

55
Q

TXV is rated in what?

A

Tonnage

56
Q

The bulb of a externally equalized TXV should be mounted upstream or downstream of the equalization port?

A

Downstream

57
Q

Cap Tube minimum and maximum length?

A

6 inches minimum & 18 Inches maximum

58
Q

Capillary Tubes are critically charged systems. True or False?

A

True

59
Q

Bubble point is directly related to what?

A

Subcooling

60
Q

High side floats are critically charged? True or flase?

A

True

61
Q

The first symptom of an overcharge of a system using a high side float would be?

A

Flood back to the compressor

62
Q

High side floats maintain what?

A

A constant liquid level in the high side of the system

63
Q

The first symptom of an overcharge in a system using a low side float would be?

A

High Discharge Pressure

64
Q

An AEV’s opening force?

A

Spring Pressure

65
Q

An AEV’s Closing force

A

Evaporator Pressure

66
Q

An undercharged high side float will do what to the evaporator?

A

Starve it

67
Q

What accessory will prevent overfeeding in low loads and underfeeding in high loads?

A

Accumulator

68
Q

What does nominal mean?

A

Normal conditions

69
Q

What is the range of a “c” bulb charge?

A

50 to -10 F

70
Q

What is the range of a “z” bulb charge?

A

0 to -40 F

71
Q

What is the range of a “x” bulb charge?

A

-40 to -100 F

72
Q

A gas charged bulb has a Maximum Operating Pressure. True or False?

A

True

73
Q

The best liquid line filter drier for removing moisture is?

A

Molecular Seive

74
Q

A service valve must be in which position to put your gauges on?

A

Back seat

75
Q

Oil separators remove oil in the what and return it to where?

A

Discharge line and return it to the crankcase

76
Q

Where is the best place for a sight glass?

A

Downstream of the liquid line filter drier

77
Q

Solenoid valves are gravity sensitive. True or Flase?

A

True

78
Q

A solenoid valve will do what if installed backwards?

A

Will not close

79
Q

Suction line accumulators hold what percentage of total charge?

A

50%

80
Q

Which liquid line filter drier is best for removing acids?

A

Activated Alumina

81
Q

What is the job of an EPR Valve?

A

To prevent suction pressure from getting too low

82
Q

What is an EPR’s operating action?

A

Open on Rise of Inlet

83
Q

What is the closing force of an EPR valve?

A

Spring Pressure

84
Q

What is the operating action of a CPR valve

A

Closes on Rise of Outlet

85
Q

What is the job of a CPR Valve?

A

Prevents the compressor from overamping by limiting the suction pressure the compressor see’s

86
Q

What is the opening force on a CPR valve

A

Spring Pressure

87
Q

An LAC Valve must be used in conjuction with what other device?

A

A check valve

88
Q

What is the operating action of a headmaster control valve?

A

Open on Rise of Outlet

89
Q

A Hot Gas Bypass Valve is used for what?

A

Capacity Control

90
Q

What additional device is needed if the HGBV is equipped to the outlet of the evaporator?

A

Desuperheating TXV

91
Q

Increased air velocities in an evaporator will increase or decrease the RH

A

Decrease the RH

92
Q

A draw through fan should be 2/3 in or out of the shroud?

A

2/3 in the shroud

93
Q

A blow through fan should be 2/3 in or out of the shroud?

A

2/3 out of the shroud

94
Q

A 4 way reversing valve used in a heat pump system in Canada with the reversing valve solenoid energized you must be in?

A

Cooling Mode

95
Q

A defrost differential regulator valve’s purpose is to…?

A

Lower the liquid pressure below the discharge pressure when a system is in defrost mode

96
Q

A large temperature difference will cause low RH and can dry out exposed product, True or False?

A

True

97
Q

What two characteristics of refrigerant help with oil return?

A

Refrigerant velocity and Refrigerant miscibility

98
Q

What are two application for a 3 way solenoid valve?

A

Heat Reclaim and Hot Gas Defrost

2nd Year Finals (3 decks)

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