# Refrigerant Machine Operator Test # 4

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• 1.

### What is the cooling medium of the cooling towers?

• A.

Air

• B.

Water

• C.

Air and water

• D.

Fan

A. Air
Explanation
Cooling towers use air as the cooling medium. The purpose of a cooling tower is to remove heat from a system by transferring it to the surrounding air. Water is typically circulated through the tower, and as the water flows over the tower's fill material, it is exposed to the air. The heat from the water is then transferred to the air through evaporation and convection, cooling the water in the process. Therefore, air is the main medium used for cooling in cooling towers.

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• 2.

### If the temperature outside drops b 8 deg.C, what is the equivalent drop in def.F?

• A.

4 deg.F

• B.

40 deg.F

• C.

14 deg.F

• D.

8 deg.F

C. 14 deg.F
Explanation
If the temperature outside drops by 8 deg.C, the equivalent drop in def.F can be calculated using the formula: def.F = (9/5 * deg.C) + 32. Plugging in the value of -8 deg.C, we get def.F = (9/5 * -8) + 32 = 14 deg.F. Therefore, the correct answer is 14 deg.F.

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• 3.

### The primary function of the steam eductors on the surface condenser is to:

• A.

Condense the steam

• B.

Create a vacuum

• C.

Separate the steam and air

• D.

Safety device only

B. Create a vacuum
Explanation
The primary function of the steam eductors on the surface condenser is to create a vacuum. Steam eductors use high-pressure steam to create a low-pressure area, which helps in drawing out air and other non-condensable gases from the condenser. This vacuum is necessary for efficient condensation of steam and optimal performance of the condenser. By creating a vacuum, the steam eductors ensure that the pressure inside the condenser is lower than the surrounding atmosphere, facilitating the removal of air and enhancing the condensation process.

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• 4.

### A valve that will not provide continuos flow of refrigerant through the circuit is the:

• A.

Globe valve

• B.

Service valve

• C.

Solenoid valve

• D.

TXV

C. Solenoid valve
Explanation
A solenoid valve is a type of valve that is controlled by an electric current. It is commonly used in refrigeration systems to control the flow of refrigerant. Unlike other valves such as globe valves and service valves, a solenoid valve can be opened or closed rapidly, allowing for precise control of the refrigerant flow. However, it is not designed to provide continuous flow of refrigerant through the circuit. It is typically used to regulate the flow or completely shut off the refrigerant when needed. Therefore, a solenoid valve is the correct answer.

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• 5.

### When considering the rate of BTUs rejected by the condenser, an important point for the operator to remember is:

• A.

Will increase if you oversize the tower

• B.

Will decrease as the water temperature goes down

• C.

Will increase as the velocity goes up

• D.

Will show no difference as long as the water temperature is the same

C. Will increase as the velocity goes up
Explanation
The correct answer is "will increase as the velocity goes up." This means that the rate of BTUs rejected by the condenser will increase when the velocity of the water flowing through the condenser increases. This is because higher velocity leads to better heat transfer between the water and the condenser, resulting in more BTUs being rejected.

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• 6.

### As the load on a reciprocating chiller decreases, the most correct sequence of operation is as follows

• A.

Compressor goes into hot gas by-pass, unloads and shuts off

• B.

Compressor shuts off, unloads and then goes into hot gas by-pass

• C.

Compressor unloads, then hot gas by-passes and shuts down

• D.

None of the above

C. Compressor unloads, then hot gas by-passes and shuts down
Explanation
When the load on a reciprocating chiller decreases, the compressor first unloads, which means it stops compressing refrigerant and operates at a lower capacity. After unloading, the hot gas by-pass valve opens to divert the hot refrigerant gas directly to the condenser, bypassing the compressor. Finally, the compressor shuts down completely. Therefore, the correct sequence of operation is compressor unloads, then hot gas by-passes, and shuts down.

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• 7.

### An RMO notices that the diameter of the suction line is 36" and the diameter of the discharge line is 18".  What can we determine from this statement?

• A.

The unit is piped wrong because the diameters should be opposite

• B.

The cold refrigerant vapor needs less space than a hot vapor

• C.

The high pressure line needs more diameter to handle the pressure

• D.

The higher the vapor pressure is, the less volume is needed

D. The higher the vapor pressure is, the less volume is needed
Explanation
The correct answer suggests that the higher the vapor pressure, the less volume is needed. This means that the diameter of the suction line being larger than the discharge line is intentional and correct. It indicates that the system is designed to handle high vapor pressure, which requires less volume.

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• 8.

### As an RMO, you are responsible for two air cooled split systems handling computer rooms and are required to run all year round.  These units are most likely equipped with:

• A.

Crankcase heaters and condenser damper

• B.

Crankcase heater and hot gas by-pass

• C.

Condenser damper and VFD

• D.

Condenser damper and hot gas by-pass

D. Condenser damper and hot gas by-pass
Explanation
The correct answer is condenser damper and hot gas by-pass. In computer rooms, it is important to maintain a stable temperature throughout the year. The condenser damper allows for the regulation of air flow in the condenser unit, ensuring efficient heat transfer. The hot gas by-pass valve helps control the refrigerant flow and temperature, allowing the system to adjust to varying cooling demands. These features ensure that the air cooled split systems can operate effectively and continuously in order to maintain the desired temperature in the computer rooms.

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• 9.

### You notice that the second stage compressor on your reciprocating chiller has foaming in the oil sight glass.  As an operator you should check for:

• A.

Excessive charge

• B.

Burnt out crankcase heater

• C.

Moisture in the system

• D.

Too much oil

B. Burnt out crankcase heater
Explanation
Foaming in the oil sight glass of the second stage compressor indicates a potential issue with the crankcase heater. The crankcase heater is responsible for preventing the oil from becoming too cold and thick, which can lead to foaming. If the crankcase heater is burnt out or not functioning properly, it can result in foaming. Therefore, as an operator, it is important to check for a burnt out crankcase heater when encountering foaming in the oil sight glass.

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• 10.

### On a water cooled chiller, the heat that is absorbed by the chilled water is:

• A.

Rejected to the ambient air as sensible heat

• B.

Rejected as latent and sensible heat heat to the ambient air

• C.

Minimal in comparison to the volume of water

• D.

Rejected by the compressor

B. Rejected as latent and sensible heat heat to the ambient air
Explanation
The heat absorbed by the chilled water in a water cooled chiller is rejected to the ambient air as both latent and sensible heat. This means that the heat is transferred to the surrounding air in two forms - sensible heat, which can be felt and measured by a thermometer, and latent heat, which is released when water vapor condenses. This dual rejection of heat helps to cool down the chilled water and maintain the desired temperature in the chiller system.

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• 11.

### Types of steam turbines include all of the following except:

• A.

Impulse steam turbines

• B.

Reaction steam turbines

• C.

Impulse reaction steam turbine

• D.

None of the above

D. None of the above
Explanation
The correct answer is "none of the above" because all three types of steam turbines mentioned in the options are actually included in the types of steam turbines. Impulse steam turbines, reaction steam turbines, and impulse reaction steam turbines are all valid types of steam turbines. Therefore, none of the options listed are excluded from the types of steam turbines.

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• 12.

### As an RMO inspecting the discharge line of a reciprocating compressor you notice a device at the furthest point away from the compressor.  This device is most likely there to:

• A.

Clean the refrigerant

• B.

Separate the moisture from the refrigerant

• C.

Return oil to the compressor

• D.

Muffle the noise from the compressor

C. Return oil to the compressor
Explanation
The device at the furthest point away from the compressor is most likely there to return oil to the compressor. This is because in a reciprocating compressor, oil is used to lubricate the moving parts and prevent wear and tear. As the refrigerant flows through the system, it can carry some of the oil with it. The device at the furthest point is designed to separate the oil from the refrigerant and return it back to the compressor, ensuring proper lubrication and preventing oil buildup in other parts of the system.

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• 13.

### Oil that has been separated from the refrigerant is returned to the compressor and tied into the

• A.

Oil charging valve

• B.

Discharge service valve

• C.

Oil pump suction

• D.

Compressor crankcase

D. Compressor crankcase
Explanation
The oil that has been separated from the refrigerant is returned to the compressor crankcase. This is where the oil is stored and circulated within the compressor. By returning the oil to the crankcase, it ensures that the compressor has a sufficient supply of oil for lubrication and cooling. This helps to maintain the efficiency and longevity of the compressor.

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• 14.

### What is the state of the refrigerant as it enters and exits the compressor?

• A.

Low temperature liquid in and high temperature liquid out

• B.

Low temperature vapor in and high temperature vapor out

• C.

Low temperature in and high temperature out

• D.

Low pressure in and high pressure out

B. Low temperature vapor in and high temperature vapor out
Explanation
As the refrigerant enters the compressor, it is in a low temperature vapor state. This means that it is in a gaseous form but at a low temperature. As the refrigerant exits the compressor, it is still in a vapor state but now at a high temperature. This indicates that the refrigerant has been compressed and its temperature has increased.

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• 15.

### When looking at a wiring diagram for a 20 ton split system, you would expect to find the following information.

• A.

The path that current takes through the system

• B.

A point to point detail of how the wires are run

• C.

A pictorial of component position

• D.

B. A point to point detail of how the wires are run
Explanation
When looking at a wiring diagram for a 20 ton split system, you would expect to find a point to point detail of how the wires are run. This means that the diagram would provide a clear and specific description of how the wires connect and run throughout the system. It would show the starting point and ending point of each wire, as well as any junctions or connections along the way. This information is crucial for understanding the electrical connections and ensuring proper installation and troubleshooting of the system.

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• 16.

### The design and sequence of operations of an automatic expansion valve causes it to:

• A.

Decrease superheat on an increase in load

• B.

Increase superheat on a decrease of load

• C.

Close on decrease in pressure

• D.

Close on an increase in pressure

D. Close on an increase in pressure
Explanation
An automatic expansion valve is designed to close when there is an increase in pressure. This is because the valve is responsible for regulating the flow of refrigerant into the evaporator coil of a refrigeration system. When there is an increase in pressure, it indicates that the evaporator coil is becoming too cold and the valve needs to close to reduce the flow of refrigerant and prevent excessive cooling. By closing the valve, the superheat (the temperature difference between the refrigerant and its boiling point) is increased, allowing for better control of the cooling process.

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• 17.

### When looking at a large semi-hermetic reciprocating compressor,  you would expect to find:

• A.

Suction and discharge lines parallel to each other

• B.

Suction and discharge lines perpendicular to each other

• C.

Depends on the amount of cylinders

• D.

Suction on top and discharge off the bottom

B. Suction and discharge lines perpendicular to each other
Explanation
In a large semi-hermetic reciprocating compressor, the suction and discharge lines are expected to be perpendicular to each other. This configuration allows for efficient flow of the refrigerant through the compressor. The perpendicular arrangement helps to minimize pressure drop and maximize the compressor's performance.

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• 18.

### The sole refrigeration engineer on duty in a building is permitted to leave the building refrigeration system is in operation only when

• A.

Lunch or dinner occur

• B.

System is in automatic operation

• C.

Relieved by another licensed refrigeration engineer

• D.

The assistant provides coverage or supervision

C. Relieved by another licensed refrigeration engineer
Explanation
The correct answer is "relieved by another licensed refrigeration engineer". This means that the sole refrigeration engineer can only leave the building when another licensed engineer takes over their responsibilities. This ensures that there is always a qualified professional present to monitor and maintain the refrigeration system, ensuring its proper operation and preventing any potential issues or emergencies.

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• 19.

### When conducting a routine tour of the plant, an RMO notices a significant increase in superheat for a reciprocating compressor. Of the following, the most likely cause of this would be?

• A.

Scale particles lodged in the TEV

• B.

Unraveling of the insulation covering the thermal bulb of the TEV

• C.

Overcharge of refrigerant

• D.

Noncondensables in the system

A. Scale particles lodged in the TEV
Explanation
The most likely cause of the significant increase in superheat for a reciprocating compressor is scale particles lodged in the TEV. Scale particles can obstruct the flow of refrigerant through the thermal expansion valve (TEV), causing it to malfunction and leading to an increase in superheat. This can result in inefficient cooling and potential damage to the compressor. The other options - unraveling of the insulation covering the thermal bulb of the TEV, overcharge of refrigerant, and noncondensables in the system - may also cause issues in the system, but they are not as likely to directly cause an increase in superheat as scale particles lodged in the TEV.

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• 20.

### An automatic purge unit is required on units:

• A.

With centrifugal compressors

• B.

Containing low pressure refrigerants

• C.

Absorption systems

• D.

Double indirect open spray systems

B. Containing low pressure refrigerants
Explanation
An automatic purge unit is required on units containing low pressure refrigerants because low pressure refrigerants have a higher tendency to leak compared to high pressure refrigerants. The automatic purge unit helps to remove any non-condensable gases that may accumulate in the system, which can lead to reduced efficiency and potential damage to the equipment. By continuously purging these gases, the unit ensures that the system operates at its optimal level and prevents any potential safety hazards.

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• 21.

### Efficiency of the refrigeration cycle is affected by the operation of the condenser. Of the following, a more efficient condenser on a centrifugal compressor results from

• A.

Raising the condenser liquid level to maximum

• B.

Produce large amounts of subcooling

• C.

• D.

Lowering the condenser pressure

B. Produce large amounts of subcooling
Explanation
A more efficient condenser on a centrifugal compressor results from producing large amounts of subcooling. Subcooling refers to cooling the refrigerant liquid below its saturation temperature. By producing large amounts of subcooling, the condenser is able to remove more heat from the refrigerant, resulting in a lower condensing temperature and improved efficiency of the refrigeration cycle. This allows the compressor to work more efficiently and reduces the energy consumption of the system.

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• 22.

### Shaft glands on a steam turbine are located:

• A.

Front and rear of turbine

• B.

Wherever the shaft emerges from the casing or steam could leak

• C.

Wherever air could leak out of the turbine

• D.

Wherever oil can leak from the lubrication system

B. Wherever the shaft emerges from the casing or steam could leak
Explanation
Shaft glands on a steam turbine are located wherever the shaft emerges from the casing or steam could leak. This is because the shaft glands are designed to prevent steam leakage from the turbine. By placing the glands at the point where the shaft emerges from the casing, any potential steam leakage can be effectively controlled and prevented.

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• 23.

### You are the RMO of a facility which contains a 750 ton centrifugal Trane chiller.  The chief ask you to order extra refrigerant for the upcoming season.  If the machine charge is determined to be 1500lbs, how much refrigerant can you store without being in violation of the code?

• A.

Whatever the chief engineer deems safe

• B.

Whatever can be tied down and stored safely

• C.

200lbs of refrigerant

• D.

330 lbs of refrigerant

D. 330 lbs of refrigerant
Explanation
The correct answer is 330 lbs of refrigerant. This is because the question asks for the maximum amount of refrigerant that can be stored without violating the code. Since the machine charge is determined to be 1500 lbs, it is safe to store up to 330 lbs of refrigerant without violating the code.

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• 24.

### When changing water to ice, what must be removed?

• A.

Specific heat

• B.

Latent heat

• C.

Sensible heat

• D.

N/A

B. Latent heat
Explanation
When changing water to ice, latent heat must be removed. Latent heat is the energy required to change the state of a substance without changing its temperature. In the case of water, when it reaches its freezing point and changes from a liquid to a solid (ice), latent heat must be removed from the water in order for this phase change to occur.

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• 25.

### A truck with 5 tons of ice stuck on the side of the road with no refrigeration.  How many BTUs is required to melt 5 tons of ice at 32 deg F to 5 tons of water at 32 deg F in 1

• A.

60,000 BTUs

• B.

1,400,000 BTUs

• C.

288,000 BTUs

• D.

Cannot be done in 1 hr.

A. 60,000 BTUs
Explanation
The correct answer is 60,000 BTUs because it takes 1 BTU to raise the temperature of 1 pound of water by 1 degree Fahrenheit. Since there are 2000 pounds in a ton, and the temperature change is 32 degrees, the total BTUs required to melt 5 tons of ice at 32 degrees Fahrenheit to 5 tons of water at 32 degrees Fahrenheit is 5 tons * 2000 pounds/ton * 32 degrees = 320,000 BTUs. However, since the question specifies that this needs to be done in 1 hour, the total BTUs required per hour is 320,000 BTUs/hour. Therefore, the correct answer is 60,000 BTUs.

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• 26.

### Packing glands on centrifugal pumps are typically made out of what types of materials?

• A.

Graphite impregnated rope or string

• B.

Ceramic and carbon with rubber retainers

• C.

Centrifugal pumps do not need packing glands

• D.

Stuffing box filled with grease

A. Graphite impregnated rope or string
Explanation
Packing glands on centrifugal pumps are typically made out of graphite impregnated rope or string. This material is commonly used because it has good lubrication properties and can withstand high temperatures and pressures. It also provides a tight seal to prevent leakage of the pumped fluid. Ceramic and carbon with rubber retainers may also be used in some cases, but graphite impregnated rope or string is the more common choice. Centrifugal pumps do require packing glands to ensure proper sealing, so the option stating that they do not need packing glands is incorrect. A stuffing box filled with grease is not a typical material for packing glands on centrifugal pumps.

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• 27.

### The job of the kingsbury bearing on a steam turbine is to:

• A.

To maintain axial clearance

• B.

To keep vertical clearance

• C.

To compensate for axial thrust

• D.

To not allow and shaft movement

C. To compensate for axial thrust
Explanation
The job of the Kingsbury bearing on a steam turbine is to compensate for axial thrust. Axial thrust refers to the force exerted on the rotor in the axial direction, which can occur due to pressure imbalances within the turbine. The Kingsbury bearing is designed to counteract this thrust and ensure that the rotor remains stable and properly aligned. By providing support and allowing for controlled movement, the bearing helps to prevent damage to the turbine and ensure its efficient operation.

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• 28.

### As an RMO you encounter a large steam turbine.  The type of device you would most likely find controlling the speed of the turbine is:

• A.

A hydraulic governor assembly

• B.

A mechanical governor assembly

• C.

An automatic over speed trip

• D.

An automatic gimple valve

A. A hydraulic governor assembly
Explanation
A hydraulic governor assembly is the most likely device to control the speed of a large steam turbine. This is because hydraulic governors use fluid pressure to regulate the turbine's speed, allowing for precise control and adjustment. Mechanical governor assemblies, on the other hand, rely on mechanical linkages and are typically used in smaller engines. An automatic overspeed trip is a safety feature that shuts down the turbine if it exceeds a certain speed, while an automatic gimple valve is used for pressure regulation and is not directly related to controlling the turbine's speed.

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• 29.

### Radial clearance in reference to a steam turbine is defined as

• A.

Distance from end to end of shaft

• B.

• C.

Distance between the top of the rotating blades and the casing

• D.

Distance between the packing and the shaft

C. Distance between the top of the rotating blades and the casing
Explanation
Radial clearance in reference to a steam turbine is the distance between the top of the rotating blades and the casing. This refers to the space or gap between the blades and the casing, allowing for thermal expansion and preventing any contact or interference between the blades and the casing during operation. It is important to maintain an appropriate radial clearance to ensure efficient and safe operation of the steam turbine.

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• 30.

### The recirculation valve on a surface condenser is controlled by the:

• A.

Hot well level control

• B.

The condensate pumps

• C.

pneumatic controller

• D.

Oil pump pressure

A. Hot well level control
Explanation
The recirculation valve on a surface condenser is controlled by the hot well level control. The hot well level control is responsible for maintaining the desired level of water in the hot well, which is the collection point for condensed steam. By controlling the hot well level, the recirculation valve can be adjusted to regulate the flow of condensed steam back into the condenser, ensuring efficient operation and preventing overflow or underflow in the hot well.

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• 31.

### After condensate water leaves the recirculation valve, where does it go?

• A.

Back to the boiler

• B.

Down the drain back

• C.

Back to the hot well for priming

• D.

Back to turbine

C. Back to the hot well for priming
Explanation
After condensate water leaves the recirculation valve, it goes back to the hot well for priming. The hot well is a reservoir that collects and stores condensate water from various parts of the system. Priming refers to the process of returning the condensate water back to the boiler for reuse. This ensures that the water is properly treated and heated before being circulated back into the system.

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• 32.

### As an RMO running a reciprocating chiller, you notice oil foaming the sight glass.  The cause for this condition could be:

• A.

A sudden drop in crankcase pressure

• B.

A faulty crankcase heater

• C.

Liquid refrigerant mixing with the oil in the off cycle

• D.

All of the above

D. All of the above
Explanation
The correct answer is "all of the above". This means that all three options mentioned in the question could be the cause for the condition of oil foaming in the sight glass of the reciprocating chiller. A sudden drop in crankcase pressure, a faulty crankcase heater, and liquid refrigerant mixing with the oil in the off cycle can all contribute to the foaming of oil in the sight glass.

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• 33.

### What is the diaphragm of the power assembly of a TEV made of?

• A.

Copper

• B.

Flexible rubber

• C.

Flexible steel

• D.

N/A

C. Flexible steel
Explanation
The diaphragm of the power assembly of a TEV is made of flexible steel. This material is chosen because it allows for movement and flexibility while maintaining strength and durability. The flexible steel diaphragm is able to withstand the pressure and temperature changes that occur in the power assembly of a TEV, ensuring proper functioning and efficient control of the refrigerant flow.

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• 34.

### An automatic oil trap is installed in the high side of a refrigeration system.  When the float of the traps lifts it allows:

• A.

Hot oil to defrost the coils

• B.

Hot oil to go through the stuffing box

• C.

Oil to drain off into the receiver reservoir

• D.

Explanation
The automatic oil trap is designed to separate the oil from the refrigerant in the high side of the refrigeration system. When the float of the trap lifts, it allows the oil to leave the trap and return to the compressor. This ensures that the oil is properly circulated and lubricates the compressor, preventing any potential damage or wear. By returning the oil to the compressor, the system can operate efficiently and effectively.

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• 35.

### In commercial refrigeration, the room thermostat controls the liquid line solenoid valve but the control that starts and stops the compressor is the :

• A.

Low temperature stat

• B.

Low pressure cut-out

• C.

Low pressure control

• D.

Low oil safety

C. Low pressure control
Explanation
The low pressure control is responsible for starting and stopping the compressor in commercial refrigeration. This control ensures that the system operates within the desired pressure range by monitoring the pressure in the refrigeration system. When the pressure drops below a certain threshold, the low pressure control will signal the compressor to start, and when the pressure rises above the set limit, it will signal the compressor to stop. This control helps maintain the proper functioning of the refrigeration system and prevents damage due to low or high pressure conditions.

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• 36.

### An RMO is inspecting a centrifugal pump and he notices excessive water leaking from the mechanical seal.  The RMO should:

• A.

Tighten evenly to get a steady drip

• B.

This is normal for a mechanical seal

• C.

Shut down the pump, turn on the standby and call for pump service

• D.

Order a new pump because mechanical seals cannot be replaced

C. Shut down the pump, turn on the standby and call for pump service
Explanation
The correct answer is to shut down the pump, turn on the standby, and call for pump service. Excessive water leaking from the mechanical seal indicates a problem with the seal, which can lead to further damage if not addressed. Shutting down the pump and turning on the standby ensures that the pump is not running while the issue is being resolved. Calling for pump service is necessary to have a professional inspect and repair the mechanical seal.

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• 37.

### Mechanical seals are typically made of:

• A.

Carbon and stainless steel

• B.

Ceramic and carbon

• C.

Ceramic and graphite

• D.

Graphite impregnated rope or string

A. Carbon and stainless steel
Explanation
Mechanical seals are typically made of carbon and stainless steel because these materials offer excellent durability and resistance to corrosion. Carbon is used for the seal faces because it has self-lubricating properties and can withstand high temperatures. Stainless steel is used for the other components of the seal, such as the springs and housing, because it provides strength and resistance to chemical attacks. The combination of carbon and stainless steel ensures a reliable and long-lasting seal in various industrial applications.

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• 38.

### All of the following can cause you to lose your vacuum on the surface condenser  except:

• A.

Open atmospheric vent valve

• B.

Ruptured cooling water tube

• C.

No priming water in the hot well

• D.

D. A sudden drop in load
Explanation
A sudden drop in load does not directly cause a loss of vacuum in a surface condenser. The vacuum in a surface condenser is maintained by the removal of non-condensable gases and the cooling of the steam by the cooling water. An open atmospheric vent valve would allow air to enter the condenser, disrupting the vacuum. A ruptured cooling water tube would reduce the cooling water flow, affecting the condensation process. The absence of priming water in the hot well would also impact the condensation process. However, a sudden drop in load does not directly affect the vacuum in the surface condenser.

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• 39.

### The medium/mediums for cooling in an evaporative condenser is/are:

• A.

Air only

• B.

Refrigerant and water

• C.

Water and air

• D.

Glycol and air

C. Water and air
Explanation
The correct answer is water and air. Evaporative condensers use water and air as the mediums for cooling. The process involves the evaporation of water which absorbs heat from the refrigerant, thereby cooling it. The water is circulated over a heat exchanger while air is blown through the exchanger, facilitating the evaporation process and dissipating the heat. This combination of water and air is essential for efficient cooling in evaporative condensers.

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• 40.

### Ejector pumps are employed on oil tanks of a centrifugal system to:

• A.

Vent air from the oil tank

• B.

Vent refrigerant from the oil tank

• C.

Return oil from the condenser

• D.

Return oil from the chiller

D. Return oil from the chiller
Explanation
Ejector pumps are used on oil tanks of a centrifugal system to return oil from the chiller. This means that the ejector pumps help in pumping the oil from the chiller back into the oil tank.

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• 41.

### Of the following, the action that controls the capacity of the centrifugal compressor provided with variable vane control:

• A.

Altering the size of the passage wheel

• B.

Controlling the cylinder unloaders as capacity changes

• C.

Changing the compressor clearance spac

• D.

Changing the tip speed of the compressor wheel

A. Altering the size of the passage wheel
Explanation
The action that controls the capacity of the centrifugal compressor provided with variable vane control is altering the size of the passage wheel. By changing the size of the passage wheel, the flow rate of the gas entering the compressor can be adjusted, thereby controlling the capacity of the compressor. This allows for flexibility in matching the compressor's output to the required demand, making it an effective method of capacity control.

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• 42.

### After completing repair to a refrigeration system, you leak check the system with your electronic leak detector.  After no leaks are found, proper disposal of the R-22 and nitrogen mix to :

• A.

Separate refrigerant from nitrogen and vent

• B.

Recover the mixture and mark to be destroyed

• C.

Vent the mixture to the outside air

• D.

You cannot use R-22 for this purpose

C. Vent the mixture to the outside air
Explanation
After completing the repair to the refrigeration system and confirming that there are no leaks, the proper disposal method for the R-22 and nitrogen mix is to vent the mixture to the outside air. This means releasing the mixture into the atmosphere. This is the correct answer because venting the mixture is a common practice for disposing of refrigerants, especially when there are no leaks present. However, it is important to note that venting refrigerants is not environmentally friendly and should be avoided whenever possible.

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• 43.

### It has been determined that the oil level in a particular refrigeration system is low, additional oil should be charged into the system by

• A.

Pumping it through the suction service valve

• B.

Pumping it into the compressor crankcase

• C.

Pumping it into the king valve

• D.

Using the gauge manifold to draw through both service valves simultaneously

B. Pumping it into the compressor crankcase
Explanation
When the oil level in a refrigeration system is low, additional oil should be charged into the system by pumping it into the compressor crankcase. The compressor crankcase is the part of the system where the compressor is located, and it is designed to hold and distribute the oil throughout the system. By pumping the oil directly into the compressor crankcase, it ensures that the oil will be properly distributed to lubricate the compressor and other components of the system, preventing damage and ensuring efficient operation.

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• 44.

### Solenoid valves are characterized by an electromagnet.  Which of the following will take place when a normally close solenoid is energized?

• A.

Valve disc will rotate 180 degrees

• B.

Valve will meter flow of refrigerant to evaporator

• C.

Valve plunger will lift off the seat

• D.

Magnetic force will close contact

C. Valve plunger will lift off the seat
Explanation
When a normally closed solenoid is energized, the valve plunger will lift off the seat. This is because the electromagnetic force generated by the solenoid causes the plunger to move upwards, creating an opening between the plunger and the seat. This allows the flow of fluid or gas through the valve, enabling the passage of refrigerant to the evaporator or any other intended application.

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• 45.

### Which of the following conditions will cause a system's compressor to pump down?

• A.

A rise in space temperature

• B.

• C.

A decrease in space temperature

• D.

A high differential setting on the low pressure controller

C. A decrease in space temperature
Explanation
A decrease in space temperature will cause a system's compressor to pump down because when the space temperature decreases, the demand for cooling decreases as well. As a result, the compressor will continue to run until the desired temperature is reached, and then it will shut off to prevent overcooling. This process is known as pumping down, where the refrigerant is pumped out of the evaporator and into the condenser until the system reaches a lower pressure and temperature.

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• 46.

### A systems condenser  water pump has been shut down for service.  When it is turned back on, it is discovered that it is not moving water.  What should the RMO do?

• A.

Check the shaft bearings for grease

• B.

Check the contacts with the voltmeter for correct voltage

• C.

Open the petcock and bleed air from volute

• D.

Bleed excess water pressure from the bottom plug

C. Open the petcock and bleed air from volute
Explanation
The RMO should open the petcock and bleed air from the volute. When the condenser water pump is shut down for service, air can enter the system and become trapped in the volute, preventing the pump from moving water. Bleeding the air from the volute will allow water to flow properly through the pump. Checking the shaft bearings for grease, checking the contacts with a voltmeter for correct voltage, and bleeding excess water pressure from the bottom plug are not relevant actions in this scenario.

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• 47.

### If the thermal bulb is clamped to the pipe right after expansion valve, what would take place?

• A.

The expansion valve would continually flood the coil

• B.

The expansion valve would freeze in the wide open position

• C.

This is incorrect and would starve the cooling coil

• D.

Oil and moisture would likely accumulate

C. This is incorrect and would starve the cooling coil
Explanation
If the thermal bulb is clamped to the pipe right after the expansion valve, it would be incorrect and would starve the cooling coil. This means that the expansion valve would not be able to properly regulate the flow of refrigerant into the coil, resulting in insufficient cooling. This can lead to poor performance and decreased efficiency of the cooling system. Additionally, the accumulation of oil and moisture is likely to occur in this situation.

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• 48.

### There are two refrigerating systems. System "A" operates with a suction pressure of 18 PSIG and a speed of 230 RPM.  It is absorbing 800 BTUs per minute in its evaporator.  The second system "B" is operating with a suction pressure of 22 PSIG and a speed of 300 RPM.  It is absorbing 600 BTUs per minute from a brine tank.  From the data given it can be said that:

• A.

"A" is producing three tons and "B" is producing for tons

• B.

"A" is producing four tons and "B" is producing four tons

• C.

"A" is producing four tons and "B" is producing three tons

• D.

"A" is producing three tons and "B" is producing three tons

C. "A" is producing four tons and "B" is producing three tons
Explanation
Based on the given information, the cooling capacity of a refrigerating system is directly proportional to the amount of heat absorbed per unit of time. System "A" is absorbing 800 BTUs per minute, while system "B" is absorbing 600 BTUs per minute. Therefore, system "A" has a higher cooling capacity than system "B". Since one ton of refrigeration is equivalent to 12,000 BTUs per hour, it can be concluded that system "A" is producing four tons (48,000 BTUs per hour) and system "B" is producing three tons (36,000 BTUs per hour).

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• 49.

### Which of the following statements should be imprinted on the body of a fusible plug?

• A.

Temperature at which the fusible member melts

• B.

Date manufactured

• C.

Busting pressure

• D.

Maximum operating pressure

A. Temperature at which the fusible member melts
Explanation
The correct answer is "temperature at which the fusible member melts". This statement should be imprinted on the body of a fusible plug because it is crucial information for the proper functioning of the plug. The fusible member is designed to melt at a specific temperature, allowing for the release of pressure in the event of overheating or excessive pressure. Knowing this temperature is essential for maintaining the safety and effectiveness of the fusible plug.

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• 50.

### While inspecting the machine room, the compressor is cycling on and off, what is causing the compressor to cycle on and off?

• A.

Refrigerant overcharge

• B.

Refrigerant undercharge

• C.

Compressor valves problems

• D.

Non condensables in the system