Refrigerant Machine Operator Test

A three-way valve is the correct choice when installing a service valve to isolate a dual pressure device while keeping the system in service. A three-way valve has three ports, allowing for the diversion of fluid flow between two different paths. In this case, one port can be used to connect to the dual pressure device, while the other two ports can be used to maintain the flow of fluid through the system. This configuration allows for the isolation of the dual pressure device without interrupting the operation of the system.

The reason why a spring loaded PRV is better to use than a fusible plug is because a fusible plug cannot reset. Once it has been activated and melted, it needs to be replaced. On the other hand, a spring loaded PRV can be reset after it has relieved the pressure, making it more convenient and cost-effective in the long run. Additionally, spring loaded PRVs are generally larger in size, allowing them to handle higher pressure and flow rates.

When working in a facility where the refrigerant has been changed from a flammable refrigerant to R-22, it is important to ensure safety while brazing metal. The correct answer states that the flame must be enclosed and vented to open air. This is necessary because R-22 is not a flammable refrigerant, so there is no risk of ignition. However, it is still crucial to enclose the flame and vent it to open air to prevent any potential hazards or accidents. This ensures that the brazing process is done safely and without any risk to the facility or personnel.

Butane requires approval for use by the NYC Fire Department because it is a highly flammable refrigerant. The NYC Fire Department regulates the use of flammable substances to ensure the safety of the public and prevent potential fire hazards. Therefore, approval is necessary before butane can be used as a refrigerant in NYC.

In an emergency situation where it is necessary to dump refrigerant into a sewer, it is crucial to do so under the supervision of the fire department. This is because the fire department has the expertise and resources to ensure that the process is carried out safely and without causing harm to the environment or public health. Dumping refrigerant into a sewer without proper supervision can lead to contamination of water sources and pose a risk to the community. Therefore, it is essential to have the guidance and oversight of the fire department in such circumstances.

Using a factory-made 90° elbow and brazing it is the best way to make a 90° elbow when installing a pipeline. This is because factory-made elbows are specifically designed for this purpose and ensure a precise and secure connection. Brazing provides a strong and leak-proof joint, ensuring the integrity of the pipeline. Using bend pipe may not provide the same level of accuracy and reliability. Flexible tubing may not be suitable for all pipeline applications and may not provide the same level of structural stability. Using two 45° elbows can be an alternative, but it may require more space and fittings, increasing the complexity and cost of the installation.

When changing water to ice, latent heat must be removed. Latent heat is the heat energy required to change the state of a substance without changing its temperature. In the case of water, when it changes from a liquid to a solid state (freezing), latent heat must be removed from the water in order for it to solidify into ice. This is because the water molecules need to release energy in order to slow down and arrange themselves into a solid structure.

The correct answer is to change the center belt and all other belts. This is because if the center belt is worn, it is likely that the other belts are also worn or nearing the end of their lifespan. Changing all the belts ensures that the motor will continue to function properly and avoids potential issues caused by worn belts.

A brazed joint is a type of joint that is created by heating two metal pieces and melting a filler metal into the joint. This process creates a strong and durable connection between the two pieces. The most correct way to describe a brazed joint is as a gas tight fitting. This is because the melted filler metal forms a solid bond between the two pieces, creating a seal that is resistant to gas or fluid leakage. The other options, such as pressure fitting or starting to melt at specific temperatures, do not accurately describe the nature of a brazed joint.

The correct answer is "ODORLESS" because R-22 is a type of refrigerant that does not have a distinct smell. This is important to know because if there is a leak or release of R-22, it may not be immediately detectable by odor, and other means of detection would need to be used.

If one of the hot wires in a compressor's electrical box is touching the metal box, it can create an electrical fault known as a short circuit. This can cause the metal box to become electrified, posing a risk of electric shock to anyone who touches it, including RMO workers. Therefore, the correct answer is that RMO workers can receive an electric shock if they touch it.

Semi-hermetic compressors may be better to use than hermetic compressors because hermetic compressors are fully enclosed and cannot be serviced on-site. This means that if a hermetic compressor malfunctions or requires maintenance, it cannot be repaired on-site and would need to be replaced entirely. In contrast, semi-hermetic compressors can be serviced on-site, allowing for easier maintenance and potentially reducing downtime and costs.

The correct answer is 1.2 of design pressure (at least) because when replacing the gauge on the high side of the refrigeration system, it is important to ensure that the new gauge can handle the pressure of the system. The pressure graduation rate should be at least 1.2 times the design pressure to provide a safety margin and prevent the gauge from rupturing. Additionally, the answer mentions that the rupture guard also needs to be replaced, indicating the need for a gauge that can handle high pressures. A compound gauge is suitable for this purpose as it can measure both positive and negative pressures.

Using warm water to increase the release rate of refrigerant from the drum is a common practice when charging an R-12 reciprocating refrigeration system. However, the water temperature should not exceed 90°F. If the water temperature is too high, it can cause the refrigerant to vaporize too quickly, leading to inefficient charging and potential damage to the system. Therefore, 90°F is the maximum temperature that should be used to ensure proper charging of the system.

If an electric motor is rewound to cut resistance by 1/2, all other factors being equal, the motor power would increase by a factor of 2. This is because power is directly proportional to the square of the current passing through the motor. By reducing the resistance, the current passing through the motor would increase, resulting in a power increase. Since power is proportional to the square of the current, halving the resistance would double the current, leading to a power increase by a factor of 2.

An automatic purge unit is required for refrigerating systems operating below atmospheric pressure because these systems are more prone to air and moisture ingress. Operating below atmospheric pressure creates a vacuum, which can cause air and moisture to leak into the system. The automatic purge unit helps to remove any air and moisture that enters the system, ensuring optimal performance and preventing damage to the system components.

To check if a newly purchased thermometer is working properly, one can touch it to a bucket of ice or ice water. This is because ice water has a known temperature of 0 degrees Celsius or 32 degrees Fahrenheit. By touching the thermometer to the ice water, one can verify if the reading on the thermometer matches the expected temperature. If the thermometer is functioning correctly, it should show a temperature close to 0 degrees Celsius or 32 degrees Fahrenheit. Comparing it to other thermometers or a specific brand is not necessary for this basic functionality test.

Direct systems are most likely to leak refrigerant in building spaces that are being cooled. This is because direct systems have a direct connection between the refrigerant and the building space, which increases the chances of leaks occurring. In contrast, indirect systems, both closed and open, have a separation between the refrigerant and the building space, reducing the likelihood of refrigerant leaks.

According to the NYC Fire Code classification of refrigerants, ammonia would fall under Group 2.

The correct answer is WATTS = VOLTS X AMPS X POWER FACTOR. In a refrigeration plant, the power consumption of a small induction refrigeration motor running on AC current can be determined by multiplying the voltage, current, and power factor. The power factor represents the efficiency of the motor and takes into account the phase difference between the voltage and current waveforms. By including the power factor in the calculation, the true power consumption of the motor can be accurately determined.

The purpose of having a service valve stem cap is to protect the valve from being inadvertently turned from its position and from being damaged. The cap acts as a barrier, preventing any accidental movements or tampering with the valve, which could potentially cause harm or disrupt its functioning. Additionally, the cap also provides protection against external factors such as dirt, debris, and moisture, which could lead to damage or corrosion of the valve.

The correct answer is A3. In the ANSI/ASHRAE refrigerant safety classification, A3 refers to refrigerants that are flammable. Flammable refrigerants pose a higher risk in terms of fire safety compared to non-flammable refrigerants. They have a lower ignition point and can easily ignite if exposed to an ignition source. It is important to handle and store flammable refrigerants with caution to minimize the risk of fire accidents.

The correct answer is "METAL" because the TEV diaphragm, which stands for Thermostatic Expansion Valve diaphragm, is typically made of metal. This is because the diaphragm needs to be strong and durable to withstand the pressure and temperature changes in the valve. Metal is a suitable material for this purpose as it can provide the necessary strength and stability.

According to the safety hand book, a 60 lb container can recover up to 45 lbs of refrigerant.

Ammonia belongs to safety group 2, B2. This classification indicates that ammonia is a hazardous substance that can cause both immediate and long-term health effects. It is moderately hazardous and requires caution when handling and storing. The B2 classification signifies that ammonia is a flammable gas, which further emphasizes the need for safety precautions to prevent accidents and fires.

A centrifugal pump is considered a non-positive displacement pump because it uses centrifugal force to transfer fluid from the inlet to the outlet. It does not rely on the creation of a sealed chamber or the movement of mechanical parts to displace the fluid. Instead, it uses an impeller to spin the fluid and create a centrifugal force, which pushes the fluid outwards towards the outlet. This design allows for continuous flow and high flow rates, making it suitable for applications where a steady flow is required.

A cold front causes a sharp drop in outside air temperature (O.A.T.). In this condition, the thermostat would cause the solenoid valve to close. As a result, the compressor would pump down the system and shut down on low pressure. This is the most likely effect because when the solenoid valve closes, it restricts the flow of refrigerant, causing the compressor to pump down the system and eventually shut down due to low pressure.

Charging with liquid can cause water in the tubes to freeze. This can lead to blockages and reduced efficiency in the system. Charging with vapor, on the other hand, allows for a controlled flow of refrigerant without the risk of freezing water in the tubes.

If the spring in the TEV (Thermal Expansion Valve) were to break, it would result in the flooding of the evaporator. The TEV is responsible for regulating the flow of refrigerant into the evaporator coil. The spring in the TEV controls the opening and closing of the valve, allowing the correct amount of refrigerant to enter the evaporator. If the spring breaks, the valve will remain fully open, causing an excessive amount of refrigerant to enter the evaporator. This will lead to flooding, which can disrupt the heat transfer process and potentially damage the system.

The correct answer is B3. This is because ASHRAE safety groups are classified based on their toxicity and flammability. Group B3 indicates that the substance is highly toxic and can cause serious health effects even at low levels of exposure. Therefore, it is considered the most dangerous among the given options.

The adjustment of the impeller inlet guide pre-rotation vanes is most likely to achieve capacity control in a centrifugal compressor. This is because the impeller inlet guide vanes control the flow of gas into the impeller, which directly affects the compressor's capacity. By adjusting these vanes, the operator can regulate the amount of gas entering the compressor, thereby controlling its capacity. This allows for efficient operation and optimal performance of the centrifugal compressor.

The most common metering device used today in a reciprocating commercial refrigeration system over 3 tons is the thermostatic expansion valve. This valve is designed to regulate the flow of refrigerant into the evaporator based on the temperature and pressure conditions. It ensures that the right amount of refrigerant is supplied to the evaporator to maintain the desired cooling temperature. The thermostatic expansion valve is preferred over other options like the automatic expansion valve, low side float, and high side float due to its ability to provide precise control and efficient operation.

The correct answer is "ALL OF THE ABOVE". R-11 and R-123 refrigerants are known to be oxygen depleting, heavier than air, and are classified as class-1 and class-2 substances defined by the EPA.

Orifice plates may be used as a metering device component in a centrifugal system. The vessel in which they are contained can also serve as an economizer. An economizer is a device that recovers heat from the exhaust gases of a system and uses it to preheat the incoming fluid, thus reducing energy consumption. In this case, the vessel containing the orifice plates can act as an economizer by utilizing the heat from the system to preheat the fluid before it enters the centrifugal system, thereby saving energy.

When properly purging, it is important to stop when the pressure ceases to drop. This means that all the air or gas that needed to be purged from the system has been successfully removed. Continuing to purge beyond this point would be unnecessary and could potentially lead to over-purging or damaging the system. Therefore, stopping when the pressure ceases to drop ensures that the purging process is completed efficiently and effectively.

In a refrigeration system that includes a forced draft cooling tower, the heat that is removed from the building is finally rejected as heat of evaporation of the cooling tower. This means that the heat is transferred to the cooling tower, where it is used to evaporate water and remove heat from the system. The evaporated water is then released into the atmosphere, effectively rejecting the heat from the system. This is a common method of heat rejection in refrigeration systems that use cooling towers.

ASHRAE 15 is the correct answer because it is a standard developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) specifically for safety requirements in refrigeration systems. This standard provides guidelines for the design, construction, installation, and maintenance of refrigeration systems to ensure the safety of personnel working in machine rooms. ARI-700 and ARI-740 are not relevant to machine room safety standards, and although ASHRAE 34 is a standard for refrigerant designations and safety classifications, it does not specifically address machine room safety.

The most probable cause of the knocking in the reciprocating compressor is liquid slugging. Liquid slugging occurs when liquid refrigerant enters the compressor's cylinders, causing damage to the piston, connecting rods, and other internal components. This can lead to knocking sounds and potential damage to the compressor.

The correct answer is "DIFFERENCE IN PRESSURE BETWEEN HIGH AND LOW SIDES". The amount of refrigerant that flows through the orifice plate is determined by the difference in pressure between the high and low sides of the system. This pressure difference creates a pressure drop across the orifice, causing the refrigerant to flow through it. The larger the pressure difference, the higher the flow rate of the refrigerant. Therefore, the pressure difference is a crucial factor in determining the amount of refrigerant that flows through the orifice plate.

A pump affects the pressure of a fluid or gas by raising it. When a pump is used, it creates a force that increases the pressure of the fluid or gas, pushing it to move from an area of lower pressure to an area of higher pressure. This process is commonly used in various applications such as pumping water, fuel, or air, where the pump raises the pressure to ensure the fluid or gas flows efficiently through a system or reaches a desired location.

A relief valve is designed to protect a refrigerating system by releasing excess pressure when it reaches a certain level. The design pressure is the specific pressure that the system is designed to handle without any damage or failure. Therefore, a RMO (Refrigeration Maintenance Operator) would expect the relief valve to start functioning at the design pressure, as this is the pressure that the system is intended to operate within. Starting the relief valve at any other pressure, such as 5% over design pressure or 20% below design pressure, could potentially cause damage to the system or prevent it from operating efficiently. The recommended operating pressure for normal cooling conditions may be a guideline, but the design pressure is the critical factor in determining when the relief valve should start functioning.

R-22 is not used as a cooling medium in an indirect system because it is a type of refrigerant that is commonly used in direct systems, such as air conditioning units and heat pumps. R-22 is not suitable for indirect systems because it can cause corrosion and damage to the components of the system. In indirect systems, other cooling mediums such as calcium chloride, glycol, and sodium chloride are used instead.

The correct answer is 213. When operating a refrigeration machine condenser using R-22 refrigerant, the compressor head pressure is directly related to the temperature of the cooling water. In this case, the cooling water is being supplied at 85°F and leaving at 95°F. As the cooling water temperature increases, the compressor head pressure also increases. Therefore, the compressor head pressure should be most nearly 213 psi.

The correct answer is "HIGHLY SUPERHEATED VAPOR." When running three compressors, the refrigerant leaving the third compressor would be in a highly superheated vapor state. This means that the refrigerant has absorbed a significant amount of heat and is mostly in a gaseous state with little to no liquid present. Superheating occurs when the refrigerant's temperature is raised above its saturation temperature, resulting in a highly heated vapor.

Di-chromates can be added to brine solutions to reduce corrosion and the amount of rust formed. Di-chromates act as corrosion inhibitors by forming a protective layer on the metal surface, preventing it from coming into contact with the corrosive environment. This protective layer acts as a barrier, reducing the rate of corrosion and rust formation. Therefore, the addition of di-chromates to brine solutions is an effective method to mitigate the corrosion disadvantage associated with using brines as a cooling medium.

The power head of a TXV (Thermostatic Expansion Valve) is color coded to match the refrigerant charge in the system. In this case, if the power head was charged with R-22 refrigerant, the color of the power head would be GREEN.

Excessive superheat at the evaporator outlet can be caused by any of the above mentioned reasons. A starved evaporator occurs when there is insufficient refrigerant flow to absorb the heat, resulting in high superheat. A leak in the system can cause a loss of refrigerant, leading to reduced cooling capacity and increased superheat. Similarly, a low refrigerant charge can also result in insufficient cooling and high superheat. Therefore, all three options can potentially cause excessive superheat at the evaporator outlet.

An increase in compressor head pressure would be the first evidence of a failure to maintain water treatment in the condenser water. This is because when water treatment is not properly maintained, it can lead to the accumulation of impurities and deposits in the condenser. These impurities can restrict the flow of water through the condenser, causing an increase in head pressure in the compressor as it has to work harder to pump the refrigerant through the system.

Capacity control in a reciprocating compressor is typically achieved by opening the suction valves with some form of control. By adjusting the suction valves, the amount of gas entering the compressor can be regulated, thereby controlling the capacity of the compressor. This allows for efficient operation and the ability to match the compressor's output to the required demand. Controlling the discharge pressure, changing the stroke and adding re-expansion volume, and returning the discharge gas to suction are not typically used methods for capacity control in a reciprocating compressor.

If the eliminator plates located below the fan in an induced draft-cooling tower have become clogged, it would most likely result in an increase in cooling tower water temperature being returned. The eliminator plates are responsible for removing water droplets from the air leaving the tower, preventing them from being carried out with the exhaust air. If these plates are clogged, they will not be able to effectively remove the water droplets, leading to an increase in the water temperature being returned to the tower.