Refrigerant Machine Operator Test #2

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Questions: 100 | Attempts: 15,258 | Updated: Mar 22, 2023

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Refrigerant Machine Operator Test #2 - Quiz

Incase you are a refrigerant machine operator and are in need of brushing up your knowledge and comprehension of this job then this is the quiz for you. It is designed to gauge how much you know.

Questions and Answers

1.

OF THE FOLLOWING CHARACTERISTICS OF REFRIGERANT, THE ONE THAT BEST DESCRIBES REFRIGERANT 22 IS:
- A.
  
  ODORLESS WHEN MIXED WITH AIR
- B.
  
  AN ETHER LIKE ODOR WHEN MIXED WITH AIR
- C.
  
  EXPLOSIVE WHEN MIXED WITH AIR
- D.
  
  BOILS AT HIGHER TEMP THAT R-12
Correct Answer
A. ODORLESS WHEN MIXED WITH AIR

Explanation
Refrigerant 22 is described as odorless when mixed with air. This means that it does not have a distinct smell when it is in a gaseous state and mixed with air.

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2.

BECAUSE OF THE LATENT HEAT LOAD, REFRIGERATION MACHINE OPERATOR WAS INSTRUCTED TO START THE RECIPROCATING PLANT FOR AIR CONDITIONING. OF THE FOLLOWING ACCORDING TO RECOMMENDED PRACTICE, THE FIRST THING TO DO IS
- A.
  
  TURN ON CHILLED WATER PUMPS AND OPEN THE BYPASS TO LIGHTER LOAD
- B.
  
  INSTALL LARGER FUSE TO TAKE THE INITIAL LOAD, AND THEN TURN ON THE COOLING TOWER FANS
- C.
  
  TURN ON CHILLED WATER PUMP, CONDENSER WATER PUMPS AND COOLING TOWER FANS
- D.
  
  SET THE THERMOSTAT A FEW DEGREES HIGHER
Correct Answer
C. TURN ON CHILLED WATER PUMP, CONDENSER WATER PUMPS AND COOLING TOWER FANS

Explanation
The correct answer is to turn on the chilled water pump, condenser water pumps, and cooling tower fans. This is because the latent heat load requires the use of the reciprocating plant for air conditioning. To effectively cool the space, the chilled water pump needs to be turned on to circulate cold water through the system. The condenser water pumps are necessary to remove heat from the condenser, and the cooling tower fans help to dissipate the heat from the cooling tower. By turning on these components, the refrigeration machine operator can ensure proper cooling and maintain the desired temperature in the space.

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3.

THE MOST IMPORTANT REASON TO USE 2 COMPRESSORS IN A CASCADE SYSTEM IS TO:
- A.
  
  ACCOMPLISH LOWER TEMPERATURE
- B.
  
  PERMIT THE USE OF INEXPENSIVE LUBRICATING OIL
- C.
  
  AVOID THE NEED FOR VERY HIGH COMPRESSION RATIOS
- D.
  
  DIVIDE THE COOLING LOAD BETWEEN 2 COMPRESSORS
Correct Answer
A. ACCOMPLISH LOWER TEMPERATURE

Explanation
Using two compressors in a cascade system allows for accomplishing lower temperatures. By having two compressors working in tandem, the system can achieve a greater cooling capacity and reach lower temperatures than a single compressor alone. This is especially beneficial in applications where extremely low temperatures are required, such as in industrial refrigeration or cryogenic systems. Additionally, using multiple compressors can provide redundancy and improve system reliability, as one compressor can continue operating if the other fails.

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4.

THE ADVANTAGE OF FORCED DRAFT OVER NATURAL DRAFT COOLING TOWER IS:
- A.
  
  THE POSSIBILITY OF LOWER WATER OUT TEMP
- B.
  
  THERE IS NO DEPENDENCE ON NATURAL WIND VELOCITY
- C.
  
  USE OF A SMALLER TOWER SIZE
- D.
  
  ALL OF THE ABOVE
Correct Answer
D. ALL OF THE ABOVE

Explanation
Forced draft cooling towers have the advantage of lower water outlet temperature compared to natural draft cooling towers. This is because forced draft cooling towers use fans to force air through the tower, resulting in better heat transfer and lower water temperatures. Additionally, forced draft cooling towers are not dependent on natural wind velocity, allowing for more consistent cooling performance. Lastly, forced draft cooling towers can be designed to be smaller in size compared to natural draft cooling towers, making them more space-efficient. Therefore, all of the given options are advantages of forced draft over natural draft cooling towers.

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5.

WHAT IS 29.92" HG IN KPA
- A.
  
  101.3
- B.
  
  101.28
- C.
  
  101.26
- D.
  
  103.2
Correct Answer
A. 101.3

Explanation
The given question is asking for the conversion of 29.92" HG to kPa. The correct answer is 101.3 kPa. This is the standard atmospheric pressure at sea level.

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6.

THE MECHANISM SITTING ABOVE THE EVAPORATOR IS KNOWN AS
- A.
  
  ECONOMIZER
- B.
  
  PURGE UNIT
- C.
  
  AIR BLEED
- D.
  
  PRESSURE RELIEF VALVE
Correct Answer
B. PURGE UNIT

Explanation
The mechanism sitting above the evaporator is known as the purge unit. The purge unit is responsible for removing any non-condensable gases, such as air or moisture, from the refrigeration system. This is important because these gases can reduce the efficiency of the system and cause damage to the components. The purge unit typically uses a combination of pressure differentials and heat to separate and remove these gases from the system, ensuring that only the desired refrigerant remains in the system.

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7.

THE RUPTURE DISK IS ALWAYS PIPED INTO THE
- A.
  
  HIGH SIDE
- B.
  
  LOW SIDE
- C.
  
  EITHER SIDE OF SYSTEM
- D.
  
  NEITHER SIDE SYSTEM
Correct Answer
B. LOW SIDE

Explanation
The rupture disk is always piped into the low side of the system. This is because the low side of the system is where the pressure is lower, and the rupture disk is designed to burst when the pressure exceeds a certain limit. By piping it into the low side, it ensures that if the pressure becomes too high, the disk will rupture and release the excess pressure safely.

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8.

CONCERNING LEAKAGE, WHICH STATEMENT IS MOST CORRECT?
- A.
  
  GATE VALVE CAUSES LESS LEAKAGE
- B.
  
  GLOBE VALVES CAUSES MORE LEAKAGE
- C.
  
  ALL VALVES ARE THE SAME
- D.
  
  GATE VALVES CAUSES MORE LEAKAGE
Correct Answer
D. GATE VALVES CAUSES MORE LEAKAGE

Explanation
Gate valves have a linear motion and a full bore design, which means that when fully open, the flow path is unrestricted. However, when partially open, the flow is restricted, leading to a higher pressure drop and potential for leakage. Globe valves, on the other hand, have a more complex design with a plug and seat arrangement, which allows for better throttling control and lower leakage rates compared to gate valves. Therefore, the statement "Gate valves cause more leakage" is the most correct.

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9.

WHAT SHAFT SEAL PREVENTS VAPOR FROM LEAKING OUT OF COMPRESSOR?
- A.
  
  STUFFING BOX
- B.
  
  ELECTRO-MECHANICAL SEAL
- C.
  
  MECHANICAL SEAL
- D.
  
  ALL OF THE ABOVE
Correct Answer
A. STUFFING BOX

Explanation
A stuffing box is a type of shaft seal that prevents vapor from leaking out of a compressor. It is a traditional and commonly used sealing method in various industries. The stuffing box consists of packing material, such as braided or molded graphite, which is compressed around the shaft to create a seal. This prevents the escape of vapor and helps maintain the desired pressure within the compressor.

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10.

A FUSIBLE PLUG MELTS AT
- A.
  
  450°F
- B.
  
  280°F
- C.
  
  212°F
- D.
  
  800°F
Correct Answer
B. 280°F

Explanation
A fusible plug is designed to melt at a specific temperature in order to prevent excessive pressure buildup in a system. In this case, the correct answer is 280°F. When the temperature reaches this point, the fusible plug will melt, allowing the pressure to be released and preventing any potential damage or danger.

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11.

WHEN WILL THE BTUs ABSORBED BY THE CONDENSING WATER BE THE GREATEST?
- A.
  
  LOW CONDENSER TEMPERATURE, LOW CONDENSER WATER TEMPERATURE
- B.
  
  HIGH CONDENSER TEMPERATURE, HIGH CONDENSER WATER TEMPERATURE
- C.
  
  HIGH CONDENSER TEMPERATURE, LOW CONDENSER WATER TEMPERATURE
- D.
  
  LOW CONDENSER TEMPERATURE, HIGH CONDENSER WATER TEMPERATURE
Correct Answer
C. HIGH CONDENSER TEMPERATURE, LOW CONDENSER WATER TEMPERATURE

Explanation
The BTUs absorbed by the condensing water will be the greatest when the condenser temperature is high and the condenser water temperature is low. This is because a high condenser temperature means that there is a larger temperature difference between the condensing refrigerant and the condensing water, allowing for more heat transfer. Additionally, a low condenser water temperature helps to maintain a larger temperature gradient, further enhancing the heat transfer process.

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12.

FLOODED EVAPORATORS HAVE HIGH HEAT TRANSFER PER SQUARE FOOT, WHAT MAY BE A DISADVANTAGE?
- A.
  
  REQUIRES A SMALLER CHARGE
- B.
  
  REQUIRES A HIGHER CHARGE
- C.
  
  REQUIRES A USE OF A TXV FOR PROPER FEED
- D.
  
  WATER HAS TO BE DRAINED DAILY
Correct Answer
B. REQUIRES A HIGHER CHARGE

Explanation
Flooded evaporators require a higher charge of refrigerant compared to other types of evaporators. This means that a larger amount of refrigerant is needed to fill the evaporator, which can be a disadvantage in terms of cost and environmental impact. A higher charge also increases the risk of refrigerant leaks and the need for regular maintenance and monitoring.

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13.

SHELL AND TUBE CONDENSERS HAVE THE ADVANTAGE OF:
- A.
  
  REMOVING HEADS FOR CLEANING THE WATER SIDES OF THE TUBES
- B.
  
  THE REFRIGERANT CONNECTIONS DOES NOT HAVE TO BE DISRUPTED
- C.
  
  USING ACID FOR CLEANING
- D.
  
  BOTH A AND B ARE CORRECT
Correct Answer
D. BOTH A AND B ARE CORRECT

Explanation
Both options A and B are correct because shell and tube condensers have the advantage of being able to remove the heads for cleaning the water sides of the tubes and the refrigerant connections do not have to be disrupted. This allows for easier maintenance and cleaning of the condenser, ensuring optimal performance and efficiency.

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14.

SHELL AND COIL CONDENSERS HAVE THE ADVANTAGE OF:
- A.
  
  REMOVING HEADS FOR CLEANING THE WATER SIDES OF THE TUBES
- B.
  
  THE REFRIGERANT CONNECTIONS DO NOT HAVE TO BE DISRUPTED
- C.
  
  HAS LESS CHANCE OF DEVELOPING LEAKS
- D.
  
  BOTH A AND B ARE CORRECT
Correct Answer
C. HAS LESS CHANCE OF DEVELOPING LEAKS

Explanation
Shell and coil condensers have the advantage of having less chance of developing leaks. This means that they are less likely to experience any leakage issues compared to other types of condensers. This can be beneficial as it reduces the risk of refrigerant leakage, which can lead to decreased efficiency and potential safety hazards. Additionally, it implies that the condenser will have a longer lifespan and require less maintenance and repair work.

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15.

HOW MANY BTUs WOULD BE REMOVED IN A 30 TON SYSTEM?
- A.
  
  12,000 PER HOUR
- B.
  
  360,000 PER MINUTE
- C.
  
  12,000 PER MINUTE
- D.
  
  360,000 PER HOUR
Correct Answer
D. 360,000 PER HOUR

Explanation
A 30-ton system would remove 12,000 BTUs per minute. Since there are 60 minutes in an hour, the total amount of BTUs removed in an hour would be 12,000 BTUs per minute multiplied by 60 minutes, which equals 360,000 BTUs per hour.

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16.

IF YOU HAVE 62 PSI AT 35°F AND 70 PSI AT 45°F, WHAT WOULD 38°F BE?
- A.
  
  66
- B.
  
  64.4
- C.
  
  65
- D.
  
  62
Correct Answer
B. 64.4

Explanation
The given question is asking for the pressure at 38°F based on the given pressures at 35°F and 45°F. To find the pressure at 38°F, we can use the concept of linear interpolation. Since the temperature is increasing, we can assume that the pressure is also increasing linearly. By calculating the slope using the given data, we can determine the pressure at 38°F. The slope is (70 PSI - 62 PSI) / (45°F - 35°F) = 0.8 PSI/°F. Now, we can calculate the pressure at 38°F by using the formula: pressure at 38°F = 62 PSI + (0.8 PSI/°F) * (38°F - 35°F) = 64.4 PSI. Therefore, the correct answer is 64.4.

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17.

COPPER USED IN REFRIGERATION SYSTEMS, LIKE IN HEAT EXCHANGERS, BECAUSE?
- A.
  
  EASY FABRICATION
- B.
  
  EASY DURABILITY
- C.
  
  HIGH THERMAL CONDUCTIVITY
- D.
  
  FLEXIBILITY
Correct Answer
C. HIGH THERMAL CONDUCTIVITY

Explanation
Copper is used in refrigeration systems, like in heat exchangers, because of its high thermal conductivity. Thermal conductivity refers to the ability of a material to conduct heat. Copper has one of the highest thermal conductivity values among common metals, making it an excellent choice for transferring heat efficiently in refrigeration systems. This property allows copper to quickly absorb and transfer heat, improving the overall performance and efficiency of the system.

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18.

THE ACCESSORIES ON THE LIQUID LINE ARE IN WHAT ORDER?
- A.
  
  SOLENOID VALVE, DRIER, AND SIGHT-GLASS
- B.
  
  RECEIVER, DRIER, SOLENOID VALVE, AND SIGHT-GLASS
- C.
  
  MUFFLER, DRIER, SIGHT-GLASS AND SOLENOID VALVE
- D.
  
  ACCUMULATOR, MUFFLER, DRIER, SIGHT-GLASS
Correct Answer
B. RECEIVER, DRIER, SOLENOID VALVE, AND SIGHT-GLASS

Explanation
The correct order of the accessories on the liquid line is receiver, drier, solenoid valve, and sight-glass. This order ensures that the refrigerant flows properly through the system. The receiver is responsible for storing excess refrigerant and preventing liquid from entering the compressor. The drier removes moisture and contaminants from the refrigerant. The solenoid valve controls the flow of refrigerant into the evaporator. The sight-glass allows technicians to visually inspect the refrigerant for any issues.

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19.

A CONDENSER IS 20' LONG AND 6' IN DIAMETER, WHAT IS THE VOLUME IN GALLONS IF 7.48 GALLONS IS 1 CU/FT?
- A.
  
  565
- B.
  
  4227
- C.
  
  1808
- D.
  
  1205
Correct Answer
B. 4227

Explanation
The volume of a cylinder can be calculated using the formula V = πr^2h, where r is the radius and h is the height. In this case, the diameter is given as 6', so the radius would be half of that, which is 3'. The length of the condenser is given as 20', so the height would be 20'. Plugging these values into the formula, we get V = π(3^2)(20) = 180π cubic feet. Since 7.48 gallons is equal to 1 cubic foot, we can convert cubic feet to gallons by multiplying by 7.48. Therefore, the volume in gallons would be 180π * 7.48 ≈ 4227.

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20.

WHAT IS THIS USED FOR?
- A.
  
  RECYCLING
- B.
  
  RECOVERY
- C.
  
  RECLAIMING
- D.
  
  PURGING
Correct Answer
B. RECOVERY

Explanation
Recovery refers to the process of retrieving or extracting useful materials or energy from waste or discarded items. In the context of recycling, recovery involves collecting and processing waste materials to reuse or convert them into new products. It helps to minimize waste generation and conserve resources by giving a second life to materials that would otherwise end up in landfills. Recovery can also involve the extraction of valuable substances or energy from industrial processes or wastewater. Overall, recovery plays a crucial role in sustainable waste management and resource conservation.

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21.

IF THE LOW PRESSURE CUTOUT CYCLES THE COMPRESSOR OFF, WHAT STARTS THE COMPRESSOR AGAIN?
- A.
  
  SOLENOID VALVE
- B.
  
  HIGH PRESSURE CUT OUT
- C.
  
  LOW PRESSURE CUT OUT
- D.
  
  THERMOSTAT
Correct Answer
C. LOW PRESSURE CUT OUT

Explanation
The low pressure cut out is responsible for cycling the compressor off when the pressure falls below a certain threshold. Once the compressor is cycled off, it needs a mechanism to start again. The low pressure cut out is designed to do just that. It detects when the pressure has reached a safe level and sends a signal to start the compressor again. Therefore, the low pressure cut out is the correct answer for what starts the compressor again.

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22.

REMOVING THE INSULATION ON THE SUCTION LINE, WITH THE ENGINE TEMPERATURE AT 85°F, WHAT WILL OCCUR?
- A.
  
  FLOODED EVAPORATOR
- B.
  
  STARVED EVAPORATOR
- C.
  
  EXCESSIVE SUPERHEAT
- D.
  
  LOW SUPERHEAT
Correct Answer
C. EXCESSIVE SUPERHEAT

Explanation
When the insulation on the suction line is removed and the engine temperature is at 85°F, excessive superheat will occur. Superheat refers to the temperature of the refrigerant gas above its boiling point. When the insulation is removed, the suction line is exposed to higher ambient temperatures, causing the refrigerant gas to become excessively heated before entering the compressor. This leads to excessive superheat, which can negatively affect the performance and efficiency of the refrigeration system.

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23.

IF YOU WERE RUNNING THREE COMPRESSORS, WHICH BEST DESCRIBES THE STATE OF REFRIGERANT LEAVING THE THIRD EVAPORATOR COIL?
- A.
  
  MOSTLY LIQUID, SOME VAPOR
- B.
  
  MOSTLY VAPOR, SOME LIQUID
- C.
  
  SUPERHEATED VAPOR
- D.
  
  HIGHLY SUPERHEATED VAPOR
Correct Answer
C. SUPERHEATED VAPOR

Explanation
When running three compressors, the refrigerant leaving the third evaporator coil would be in a state of superheated vapor. This means that the refrigerant has absorbed enough heat to completely vaporize, and then it has been further heated beyond its saturation temperature. In this state, the refrigerant is fully vaporized and any remaining liquid has been evaporated.

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24.

WHAT TYPE OF PUMP IS THIS?
- A.
  
  CENTRIFUGAL CHILLED WATER PUMP
- B.
  
  RECIPROCATING CONDENSER WATER PUMP
- C.
  
  RECIPROCATING CHILLED WATER PUMP
- D.
  
  CENTRIFUGAL CONDENSER WATER PUMP
Correct Answer
A. CENTRIFUGAL CHILLED WATER PUMP

Explanation
The correct answer is CENTRIFUGAL CHILLED WATER PUMP. This type of pump is specifically designed to circulate chilled water in a centrifugal motion. It is commonly used in HVAC systems to transfer the chilled water from the chiller to the air handling units or other cooling equipment. The centrifugal force generated by the rotating impeller of the pump helps in creating the pressure needed to move the chilled water through the system.

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25.

AN ELECTRIC MOTOR THAT IS RATED AT 3 HP WILL?
- A.
  
  USE THREE PHASE
- B.
  
  NEED A CAPACITOR
- C.
  
  USE SINGLE PHASE
- D.
  
  WILL RUN WITH REDUCED POWER OUTPUT
Correct Answer
A. USE THREE pHASE

Explanation
An electric motor that is rated at 3 HP will use three-phase power. Three-phase power is commonly used for motors with higher power ratings as it provides a more efficient and balanced power supply compared to single-phase power. This allows the motor to operate at its full power output without any reduction in performance. A capacitor is not needed in this case as it is primarily used to improve power factor and correct phase imbalances in single-phase motors.

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26.

IN A 3 STAGE CENTRIFUGAL CHILLER, WHAT HAPPENS TO THE PRESSURE AS IT REACHES THE FINAL STAGE?
- A.
  
  INCREASES
- B.
  
  DECREASES
- C.
  
  SPEED CHANGES NOT PRESSURE
- D.
  
  VOLUME CHANGES NOT PRESSURE
Correct Answer
A. INCREASES

Explanation
In a 3 stage centrifugal chiller, the pressure increases as it reaches the final stage. This is because each stage of the chiller adds more pressure to the refrigerant as it progresses through the system. As the refrigerant moves from one stage to the next, it undergoes compression, which increases its pressure. Therefore, by the time it reaches the final stage, the pressure has significantly increased.

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27.

WITH AN INDUCED DRAFT COOLING TOWER, WHAT IS THE LOWEST TEMPERATURE ATTAINABLE FOR A COOLING TOWER?
- A.
  
  WET BULB EQUAL TO DRY BULB
- B.
  
  DRY BULB SLIGHTLY LOWER THAN WET BULB
- C.
  
  DRY BULB HIGHER THAN WET BULB
- D.
  
  WET BULB CAN NEVER BE LOWER THAN DRY BULB
Correct Answer
C. DRY BULB HIGHER THAN WET BULB

Explanation
In an induced draft cooling tower, the dry bulb temperature refers to the actual air temperature, while the wet bulb temperature is the lowest temperature that can be achieved through evaporative cooling. Since the wet bulb temperature is determined by the moisture content in the air, it is always lower than the dry bulb temperature. Therefore, the correct answer is "DRY BULB HIGHER THAN WET BULB."

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28.

WHEN A COMPRESSOR IS RUNNING FINE AT FULL FLOW AND YOU THROTTLE DOWN FLOW CAUSING THE COMPRESSOR TO STOP RUNNING NORMAL (SHORT CYCLE), WHY WOULD THIS HAPPEN?
- A.
  
  DIRTY FILTER/STRAINER
- B.
  
  AIR GETTING IN SEALS
- C.
  
  LOW PRESSURE CUT OUT
- D.
  
  HIGH HEAD PRESSURE
Correct Answer
C. LOW PRESSURE CUT OUT

Explanation
When a compressor is running fine at full flow and suddenly stops running normally (short cycle) after throttling down the flow, it is likely due to a low pressure cut out. A low pressure cut out is a safety feature in compressors that shuts off the compressor when the pressure in the system drops below a certain threshold. Throttling down the flow reduces the pressure in the system, causing the low pressure cut out to activate and stop the compressor from running.

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29.

WHEN DRY BULB IS 75°F AND WET BULB IS 75°F:
- A.
  
  NOT POSSIBLE
- B.
  
  VERY LOW HUMIDITY
- C.
  
  THERMOMETER IS DEFECTIVE
- D.
  
  100% RELATIVE HUMIDITY
Correct Answer
D. 100% RELATIVE HUMIDITY

Explanation
When the dry bulb temperature and wet bulb temperature are both 75°F, it indicates that the air is saturated with moisture and cannot hold any more water vapor. This means that the relative humidity is at its maximum value of 100%.

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30.

WHEN A COMPRESSOR IS SAID TO HAVE A SAFETY HEAD THIS MEANS
- A.
  
  COMPRESSOR OPERATES WITH NORMAL PRESSURES
- B.
  
  COMPRESSOR OPERATES WITH LOW PRESSURES
- C.
  
  COMPRESSOR HAS PRESSURE RELIEF VALVE
- D.
  
  COMPRESSOR HAS HIGH PRESSURE CUT OUT
Correct Answer
C. COMPRESSOR HAS PRESSURE RELIEF VALVE

Explanation
When a compressor is said to have a safety head, it means that the compressor has a pressure relief valve. This valve is designed to release excess pressure in the compressor system to prevent any damage or failure. The pressure relief valve ensures that the pressure inside the compressor does not exceed safe limits, protecting both the compressor and the surrounding equipment or system.

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31.

THE CYLINDER UNLOADER CONTROLS CAPACITY, IS THERE ANY OTHER FUNCTION IT MAY HAVE?
- A.
  
  ASSIST WITH COMPRESSOR SHUT DOWN
- B.
  
  ASSIST WITH COMPRESSOR START UP
- C.
  
  THERE IS NO OTHER FUNCTION
- D.
  
  RELEASES PRESSURE
Correct Answer
B. ASSIST WITH COMPRESSOR START UP

Explanation
The cylinder unloader controls capacity by assisting with the compressor start up. This means that it helps the compressor to start running smoothly and efficiently. It may have other functions as well, but the given options do not mention any other functions. Therefore, the correct answer is that it assists with compressor start up.

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32.

AN OPERATOR SUSPECTS THAT SHORTED MOTOR WINDINGS HAVE CAUSED THE MOTOR OVERLOADS TO TRIP. IN ORDER TO INVESTIGATE THIS CONDITION, THE OPERATOR WOULD BE MOST CORRECT TO USE
- A.
  
  CAPACITOR
- B.
  
  VOLTMETER
- C.
  
  OHMMETER
- D.
  
  AMMETER
Correct Answer
C. OHMMETER

Explanation
The operator suspects that shorted motor windings have caused the motor overloads to trip. In order to investigate this condition, the operator would be most correct to use an ohmmeter. An ohmmeter is used to measure the resistance of a circuit or component. By using an ohmmeter, the operator can check the resistance of the motor windings. If the windings are shorted, the resistance reading will be very low or close to zero. This would confirm the suspicion that the shorted motor windings are causing the motor overloads to trip.

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33.

WHEN RECOVERING R-22, WHAT COLOR WOULD THE CYLINDER BE THAT YOU ARE STORING THE REFRIGERANT IN?
- A.
  
  YELLOW TOPS
- B.
  
  WHITE TOPS
- C.
  
  GREEN TOPS
- D.
  
  GRAY TOPS
Correct Answer
A. YELLOW TOPS

Explanation
The correct answer is YELLOW TOPS. When recovering R-22 refrigerant, the cylinder used for storing the refrigerant should have yellow tops. This color coding helps to easily identify the type of refrigerant stored in the cylinder and prevent cross-contamination. Yellow tops are specifically designated for R-22 refrigerant, ensuring proper handling and storage of this particular type of refrigerant.

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34.

IF UNLOADERS WERE TO FAIL IN THE UNLOADED POSITION, WHAT HAPPENS IN A SYSTEM USING RECIPROCATING COMPRESSOR?
- A.
  
  THE EVAPORATOR WILL STARVE
- B.
  
  CAUSE HIGH SUPERHEAT
- C.
  
  NOT ENOUGH REFRIGERANT TO COIL
- D.
  
  ALL OF THE ABOVE
Correct Answer
D. ALL OF THE ABOVE

Explanation
If the unloaders were to fail in the unloaded position in a system using a reciprocating compressor, several issues would occur. Firstly, the evaporator would starve, meaning that it would not receive enough refrigerant to properly cool the system. This would lead to high superheat, which is the temperature of the refrigerant vapor above its saturation temperature. Lastly, there would not be enough refrigerant flowing through the coil, further exacerbating the cooling issues. Therefore, all of the above statements are true and would happen if the unloaders failed in the unloaded position.

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35.

WHEN THE TEMPERATURE AND THE LOAD INCREASE AND YOU NEED TO ADD ANOTHER PUMP ONLINE, YOU WOULD:
- A.
  
  CLOSE BOTH SUCTION AND DISCHARGE
- B.
  
  OPEN BOTH SUCTION AND DISCHARGE
- C.
  
  OPEN SUCTION AND THROTTLE DISCHARGE
- D.
  
  OPEN DISCHARGE BYPASS AND CLOSE SUCTION
Correct Answer
C. OPEN SUCTION AND THROTTLE DISCHARGE

Explanation
When the temperature and load increase and another pump needs to be added online, opening the suction and throttling the discharge is the correct action to take. Opening the suction allows fluid to be drawn into the pump, while throttling the discharge restricts the flow and pressure to match the requirements of the system. This ensures that the additional pump can handle the increased temperature and load without causing any disruptions or damage to the system.

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36.

WHEN A SYSTEM DOES NOT HAVE UNLOADERS, WHAT IS NEEDED?
- A.
  
  OTHER CAPACITY CONTROL
- B.
  
  VARIABLE INLET GUIDE VANES
- C.
  
  AN ECONOMIZER
- D.
  
  SOLENOID ON LIQUID LINE
Correct Answer
A. OTHER CAPACITY CONTROL

Explanation
When a system does not have unloaders, other capacity control methods are needed. Unloaders are devices that control the capacity of a system by unloading or bypassing excess refrigerant. Without unloaders, other capacity control methods such as variable inlet guide vanes, an economizer, or a solenoid on the liquid line need to be implemented to regulate the capacity of the system. These alternative methods help to ensure that the system operates efficiently and effectively without the use of unloaders.

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37.

WHEN AN EVAPORATOR IS NOT EQUIPPED WITH AN EQUALIZER LINE, YOU WOULD MOST LIKELY FIND:
- A.
  
  FEELER BULB PLACED IN DIFFERENT AREA
- B.
  
  A DISTRIBUTOR
- C.
  
  AN AUTOMATIC EXPANSION VALVE
- D.
  
  BOTH HIGH AND LOW SIDE PRESSURES IDENTICAL
Correct Answer
B. A DISTRIBUTOR

Explanation
When an evaporator is not equipped with an equalizer line, you would most likely find a distributor. A distributor is used to evenly distribute the refrigerant flow to multiple evaporator coils. Without an equalizer line, the pressure between the inlet and outlet of the evaporator may vary, causing uneven refrigerant distribution. The distributor helps to ensure that each coil receives an equal amount of refrigerant, optimizing the cooling efficiency of the system.

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38.

WHEN YOU PLAN ON OVERHAULING A SYSTEM AND YOU HAVE RECOVERED ALL LIQUID REFRIGERANT, WHAT IS NEXT?
- A.
  
  GO AHEAD AND DO THE WORK
- B.
  
  RECOVER ALL VAPOR, THEN DO WORK
- C.
  
  SEND LIQUID NITROGEN THROUGH
- D.
  
  EVACUATE SYSTEM
Correct Answer
B. RECOVER ALL VAPOR, THEN DO WORK

Explanation
After recovering all the liquid refrigerant from the system, the next step is to recover all the vapor before proceeding with the work. This ensures that all the refrigerant is safely removed from the system, preventing any potential leaks or hazards. Once all the vapor is recovered, the work can be carried out without any risk of refrigerant contamination or damage.

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39.

WHEN THERE IS A 5 LB PRESSURE DROP ACROSS EVAPORATOR, YOU NEED AN EXTERNAL EQUALIZER LINE, WHAT HAPPENS IF IT DISCONNECTS
- A.
  
  EXCESSIVE SUPERHEAT
- B.
  
  EVAPORATOR WOULD STARVE
- C.
  
  EVAPORATOR WOULD FLOOD
- D.
  
  TEV WOULD NOT FUNCTION
Correct Answer
B. EVAPORATOR WOULD STARVE

Explanation
If the external equalizer line disconnects when there is a 5 lb pressure drop across the evaporator, the evaporator would starve. This means that the flow of refrigerant to the evaporator would be restricted or reduced, leading to insufficient cooling capacity. As a result, the evaporator may not be able to remove enough heat from the system, causing a decrease in cooling performance.

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40.

THE METERING DEVICE USED IN A CONDENSER IS A HIGH SIDE FLOAT, THIS DEVICE WILL:
- A.
  
  CONTROL THE AMOUNT OF WATER IN CONDENSER
- B.
  
  CONTROL THE AMOUNT OF REFRIGERANT IN CONDENSER
- C.
  
  KEEPS A CONSTANT PRESSURE
- D.
  
  KEEPS A CONSTANT TEMPERATURE
Correct Answer
B. CONTROL THE AMOUNT OF REFRIGERANT IN CONDENSER

Explanation
The high side float metering device is used to control the amount of refrigerant in the condenser. It regulates the flow of refrigerant into the condenser, ensuring that the correct amount is present for the cooling process. This helps to maintain the efficiency and performance of the condenser by preventing an excessive or insufficient amount of refrigerant from entering the system.

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41.

IF A LOW SIDE FLOAT IS BEING USED:
- A.
  
  PRESSURE WILL BE CONSTANT
- B.
  
  IT WILL CONTROL REFRIGERANT FLOW
- C.
  
  IT WILL CONTROL WATER FLOW
- D.
  
  TEMPERATURE IS CONSTANT
Correct Answer
B. IT WILL CONTROL REFRIGERANT FLOW

Explanation
A low side float is a device used in refrigeration systems to control the flow of refrigerant. It is typically installed on the suction line of the system and works by maintaining a constant level of refrigerant in the evaporator. As the refrigerant evaporates and flows through the system, the float valve opens or closes to regulate the amount of refrigerant entering the evaporator. This helps to maintain a consistent and controlled flow of refrigerant, ensuring efficient operation of the system.

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42.

THE HEAT THAT BOILS OFF IN A CONDENSER IS:
- A.
  
  LATENT HEAT
- B.
  
  SENSIBLE HEAT
- C.
  
  SUPERHEAT
- D.
  
  ALL OF THE ABOVE
Correct Answer
A. LATENT HEAT

Explanation
The heat that boils off in a condenser is latent heat. Latent heat refers to the heat energy required to change the state of a substance without changing its temperature. In the condenser, the vapor is condensed back into a liquid state, releasing latent heat. Sensible heat refers to the heat energy that causes a change in temperature, while superheat refers to the additional heat energy added to a substance above its boiling point. However, in the context of a condenser, the heat being boiled off is specifically latent heat.

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43.

THE CONDENSER THAT USES AIR AND WATER FOR COOLING IS THE:
- A.
  
  AIR COOLED
- B.
  
  WATER COOLED
- C.
  
  EVAPORATIVE
- D.
  
  BOTH A AND B ARE CORRECT
Correct Answer
C. EVAPORATIVE

Explanation
The correct answer is EVAPORATIVE. An evaporative condenser uses both air and water for cooling. It works by allowing water to evaporate into the air, which removes heat from the system being cooled. This type of condenser is commonly used in air conditioning systems and refrigeration units. It is an efficient and cost-effective method of cooling, particularly in dry climates.

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44.

A HERMETIC COMPRESSOR IS OPERATING WITH A LOW REFRIGERANT CHARGE. WHAT IS THE MOST LIKELY EFFECT THIS CONDITION WOULD HAVE ON THE COMPRESSOR?
- A.
  
  HEAD PRESSURE WOULD RISE
- B.
  
  COMPRESSOR WOULD OPERATE AT HIGHER TEMPERATURE
- C.
  
  HAVE NO EFFECT ON THE COMPRESSOR
- D.
  
  OIL PRESSURE WOULD RISE
Correct Answer
B. COMPRESSOR WOULD OPERATE AT HIGHER TEMPERATURE

Explanation
When a hermetic compressor operates with a low refrigerant charge, it means there is not enough refrigerant circulating through the system. This can lead to inadequate cooling and cause the compressor to operate at a higher temperature. Without enough refrigerant to absorb and carry away heat, the compressor will have to work harder and generate more heat, resulting in a higher operating temperature.

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45.

A REFRIGERATION UNIT IS MEASURED IN:
- A.
  
  WATTS
- B.
  
  VOLTS
- C.
  
  BTUs
- D.
  
  TEMPERATURE
Correct Answer
C. BTUs

Explanation
A refrigeration unit is measured in BTUs (British Thermal Units). BTUs are a unit of measurement for heat energy. In the context of refrigeration, BTUs are used to measure the cooling capacity of the unit. The higher the BTU rating, the more cooling power the unit has. Watts and volts are units of electrical power, which are not directly related to the cooling capacity of a refrigeration unit. Temperature is a measure of the degree of hotness or coldness and is not used to measure the capacity of a refrigeration unit.

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46.

A CENTRIFUGAL CHILLER HAS A SUCTION PRESSURE OF 18" HG VACUUM AND DISCHARGE PRESSURE OF 6 PSIG. WHAT IS THE COMPRESSION RATIO OF THIS UNIT?
- A.
  
  3.50
- B.
  
  2.96
- C.
  
  1.75
- D.
  
  2.76
Correct Answer
A. 3.50

Explanation
The compression ratio of a centrifugal chiller is calculated by dividing the discharge pressure by the suction pressure. In this case, the discharge pressure is given as 6 PSIG and the suction pressure is given as 18" HG vacuum. To convert the suction pressure from inches of mercury to PSIG, we need to use a conversion factor. 1 inch of mercury is equal to 0.491 PSIG. Therefore, the suction pressure in PSIG is 18" HG vacuum * 0.491 PSIG/inch of mercury = 8.838 PSIG. Now we can calculate the compression ratio: 6 PSIG / 8.838 PSIG = 0.679. Therefore, the correct answer is not provided in the options.

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47.

WHAT IS A METHOD USED TO CALIBRATE A THERMOMETER?
- A.
  
  PLACE THERMOMETER IN CUP OF ICE
- B.
  
  PLACE THERMOMETER IN SUPERHEATED STEAM
- C.
  
  LOWER TEMPERATURE ON THERMOMETER
- D.
  
  RAISE TEMPERATURE ON THERMOMETER
Correct Answer
A. PLACE THERMOMETER IN CUP OF ICE

Explanation
Placing the thermometer in a cup of ice is a method used to calibrate a thermometer. This is because ice has a well-defined and constant temperature of 0 degrees Celsius (32 degrees Fahrenheit). By placing the thermometer in the ice, it allows the thermometer to adjust to this known temperature, ensuring that it is accurately calibrated.

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48.

IF HAD TO INSTALL A SOLENOID VALVE TO A SYSTEM WHICH USES 110 VOLTS AND NEEDED TO CONVERT IT TO 24 VOLTS, WHAT WOULD YOU USE?
- A.
  
  STEP UP TRANSFORMER
- B.
  
  STEP DOWN TRANSFORMER
- C.
  
  AC TO DC RECTIFICATION
- D.
  
  REWIRE CIRCUIT WITH SMALLER GAUGE WIRE
Correct Answer
B. STEP DOWN TRANSFORMER

Explanation
A step-down transformer would be used to convert the voltage from 110 volts to 24 volts. A step-down transformer has more turns on the secondary coil than the primary coil, which results in a lower output voltage. This allows the voltage to be reduced from 110 volts to 24 volts, which is the desired voltage for the solenoid valve in the system.

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49.

IF YOU HAD 38°F IN THE EVAPORATOR, WHAT SHOULD YOUR SUCTION PRESSURE BE FOR R-22
- A.
  
  66 PSIA
- B.
  
  66 PSIG
- C.
  
  76 PSIG
- D.
  
  76 PSIA
Correct Answer
B. 66 PSIG

Explanation
The correct answer is 66 PSIG. In refrigeration systems, the evaporator temperature is directly related to the suction pressure. R-22 is a common refrigerant, and for a temperature of 38°F in the evaporator, the corresponding suction pressure should be 66 PSIG. The "PSIG" unit indicates that the pressure is measured in pounds per square inch gauge, which means it is measured relative to atmospheric pressure.

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50.

AN OIL WITH LOW VISCOSITY WOULD:
- A.
  
  NOT BE USED FOR REFRIGERATION
- B.
  
  BE USED FOR ENGINE/MOTORS
- C.
  
  BE USED FOR AIR CONDITIONING
- D.
  
  BOTH B AND C ARE CORRECT
Correct Answer
A. NOT BE USED FOR REFRIGERATION

Explanation
An oil with low viscosity would not be used for refrigeration because refrigeration systems require oils with higher viscosity in order to properly lubricate the compressor and other moving parts. Low viscosity oils would not provide sufficient lubrication and could lead to increased wear and damage to the system. Therefore, it is not suitable for refrigeration applications.

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1

Quiz Review Timeline +

Our quizzes are rigorously reviewed, monitored and continuously updated by our expert board to maintain accuracy, relevance, and timeliness.

Current Version
Mar 22, 2023

Quiz Edited by
ProProfs Editorial Team
Feb 09, 2014

Quiz Created by
Catherine Halcomb

Refrigerant Machine Operator Test #2

OF THE FOLLOWING CHARACTERISTICS OF REFRIGERANT, THE ONE THAT BEST DESCRIBES REFRIGERANT 22 IS:

BECAUSE OF THE LATENT HEAT LOAD, REFRIGERATION MACHINE OPERATOR WAS INSTRUCTED TO START THE RECIPROCATING PLANT FOR AIR CONDITIONING. OF THE FOLLOWING ACCORDING TO RECOMMENDED PRACTICE, THE FIRST THING TO DO IS

THE MOST IMPORTANT REASON TO USE 2 COMPRESSORS IN A CASCADE SYSTEM IS TO:

THE ADVANTAGE OF FORCED DRAFT OVER NATURAL DRAFT COOLING TOWER IS:

WHAT IS 29.92" HG IN KPA

THE MECHANISM SITTING ABOVE THE EVAPORATOR IS KNOWN AS

THE RUPTURE DISK IS ALWAYS PIPED INTO THE

CONCERNING LEAKAGE, WHICH STATEMENT IS MOST CORRECT?

WHAT SHAFT SEAL PREVENTS VAPOR FROM LEAKING OUT OF COMPRESSOR?

A FUSIBLE PLUG MELTS AT

WHEN WILL THE BTUs ABSORBED BY THE CONDENSING WATER BE THE GREATEST?

FLOODED EVAPORATORS HAVE HIGH HEAT TRANSFER PER SQUARE FOOT, WHAT MAY BE A DISADVANTAGE?

SHELL AND TUBE CONDENSERS HAVE THE ADVANTAGE OF:

SHELL AND COIL CONDENSERS HAVE THE ADVANTAGE OF:

HOW MANY BTUs WOULD BE REMOVED IN A 30 TON SYSTEM?

IF YOU HAVE 62 PSI AT 35°F AND 70 PSI AT 45°F, WHAT WOULD 38°F BE?

COPPER USED IN REFRIGERATION SYSTEMS, LIKE IN HEAT EXCHANGERS, BECAUSE?

THE ACCESSORIES ON THE LIQUID LINE ARE IN WHAT ORDER?

A CONDENSER IS 20' LONG AND 6' IN DIAMETER, WHAT IS THE VOLUME IN GALLONS IF 7.48 GALLONS IS 1 CU/FT?

WHAT IS THIS USED FOR?

IF THE LOW PRESSURE CUTOUT CYCLES THE COMPRESSOR OFF, WHAT STARTS THE COMPRESSOR AGAIN?

REMOVING THE INSULATION ON THE SUCTION LINE, WITH THE ENGINE TEMPERATURE AT 85°F, WHAT WILL OCCUR?

IF YOU WERE RUNNING THREE COMPRESSORS, WHICH BEST DESCRIBES THE STATE OF REFRIGERANT LEAVING THE THIRD EVAPORATOR COIL?

WHAT TYPE OF PUMP IS THIS?

AN ELECTRIC MOTOR THAT IS RATED AT 3 HP WILL?

IN A 3 STAGE CENTRIFUGAL CHILLER, WHAT HAPPENS TO THE PRESSURE AS IT REACHES THE FINAL STAGE?

WITH AN INDUCED DRAFT COOLING TOWER, WHAT IS THE LOWEST TEMPERATURE ATTAINABLE FOR A COOLING TOWER?

WHEN A COMPRESSOR IS RUNNING FINE AT FULL FLOW AND YOU THROTTLE DOWN FLOW CAUSING THE COMPRESSOR TO STOP RUNNING NORMAL (SHORT CYCLE), WHY WOULD THIS HAPPEN?

WHEN DRY BULB IS 75°F AND WET BULB IS 75°F:

WHEN A COMPRESSOR IS SAID TO HAVE A SAFETY HEAD THIS MEANS

THE CYLINDER UNLOADER CONTROLS CAPACITY, IS THERE ANY OTHER FUNCTION IT MAY HAVE?

AN OPERATOR SUSPECTS THAT SHORTED MOTOR WINDINGS HAVE CAUSED THE MOTOR OVERLOADS TO TRIP. IN ORDER TO INVESTIGATE THIS CONDITION, THE OPERATOR WOULD BE MOST CORRECT TO USE

WHEN RECOVERING R-22, WHAT COLOR WOULD THE CYLINDER BE THAT YOU ARE STORING THE REFRIGERANT IN?

IF UNLOADERS WERE TO FAIL IN THE UNLOADED POSITION, WHAT HAPPENS IN A SYSTEM USING RECIPROCATING COMPRESSOR?

WHEN THE TEMPERATURE AND THE LOAD INCREASE AND YOU NEED TO ADD ANOTHER PUMP ONLINE, YOU WOULD:

WHEN A SYSTEM DOES NOT HAVE UNLOADERS, WHAT IS NEEDED?

WHEN AN EVAPORATOR IS NOT EQUIPPED WITH AN EQUALIZER LINE, YOU WOULD MOST LIKELY FIND:

WHEN YOU PLAN ON OVERHAULING A SYSTEM AND YOU HAVE RECOVERED ALL LIQUID REFRIGERANT, WHAT IS NEXT?

WHEN THERE IS A 5 LB PRESSURE DROP ACROSS EVAPORATOR, YOU NEED AN EXTERNAL EQUALIZER LINE, WHAT HAPPENS IF IT DISCONNECTS

THE METERING DEVICE USED IN A CONDENSER IS A HIGH SIDE FLOAT, THIS DEVICE WILL:

IF A LOW SIDE FLOAT IS BEING USED:

THE HEAT THAT BOILS OFF IN A CONDENSER IS:

THE CONDENSER THAT USES AIR AND WATER FOR COOLING IS THE:

A HERMETIC COMPRESSOR IS OPERATING WITH A LOW REFRIGERANT CHARGE. WHAT IS THE MOST LIKELY EFFECT THIS CONDITION WOULD HAVE ON THE COMPRESSOR?

A REFRIGERATION UNIT IS MEASURED IN:

A CENTRIFUGAL CHILLER HAS A SUCTION PRESSURE OF 18" HG VACUUM AND DISCHARGE PRESSURE OF 6 PSIG. WHAT IS THE COMPRESSION RATIO OF THIS UNIT?

WHAT IS A METHOD USED TO CALIBRATE A THERMOMETER?

IF HAD TO INSTALL A SOLENOID VALVE TO A SYSTEM WHICH USES 110 VOLTS AND NEEDED TO CONVERT IT TO 24 VOLTS, WHAT WOULD YOU USE?

IF YOU HAD 38°F IN THE EVAPORATOR, WHAT SHOULD YOUR SUCTION PRESSURE BE FOR R-22

AN OIL WITH LOW VISCOSITY WOULD: