Refrigerant Machine Operator Certification Practice Test

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 there is any issue or malfunction with a hermetic compressor, it cannot be repaired or maintained on site and would require the compressor to be completely replaced. In contrast, semi-hermetic compressors can be serviced and repaired on site, which can save time and money in case of any problems.

A spring-loaded PRV (Pressure Relief Valve) is better to use than a fusible plug because a fusible plug cannot reset. Once a fusible plug is activated and melts, it needs to be replaced entirely. This can be time-consuming and costly. On the other hand, a spring-loaded PRV can be easily reset after it has relieved the excess pressure, allowing it to continue functioning without the need for replacement. This makes the spring-loaded PRV more efficient and cost-effective in the long run.

This is the correct procedure as it ensures safety by depressurizing the system and meets the specific requirements for the gauge's pressure graduation rate, compound gauge type, and rupture guard replacement.

Using a factory-made 90° elbow and brazing it is the best way to make a 90° elbow when installing a pipeline. This method ensures a secure and leak-free connection, as the factory-made elbow is designed specifically for this purpose. Brazing provides a strong bond between the elbow and the pipe, ensuring durability and stability. Using a factory-made elbow also saves time and effort compared to bending pipe or using multiple 45° elbows.

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 may become worn soon. Changing all the belts at once ensures that the motor will continue to function properly and avoids any potential issues or failures caused by worn belts.

When installing a service valve to isolate a dual pressure device while keeping the system in service, a three-way valve would be used. A three-way valve has three ports, allowing for the diversion of flow between two different paths. In this case, the valve can be used to redirect the flow from the dual pressure device to either the system or to a bypass line, effectively isolating the device while still maintaining the flow in the system.

When faced with an emergency situation where refrigerant must be dumped into the sewer, the only appropriate action is to discharge the refrigerant under the supervision of the fire department. This ensures that the process is carried out safely and in compliance with regulations. The fire department will have the necessary expertise and resources to handle the situation and minimize any potential risks or harm to the environment.

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 protective cover that prevents any accidental movement or manipulation of the valve, ensuring that it remains in its intended position. Additionally, the cap also serves as a barrier against external elements that could potentially damage the valve, such as dust, dirt, or debris.

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 means that when making repairs, the flame should be contained within a safe enclosure and any fumes or gases produced should be directed outside to prevent any potential hazards. This is necessary to prevent the risk of fire or explosion due to the presence of the flammable refrigerant in the facility.

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 turning into ice, latent heat is released as the water molecules lose energy and slow down, causing them to form a solid structure. Therefore, to change water to ice, the latent heat needs to be removed from the water.

The correct answer is "ODORLESS". This means that R-22 does not have any smell.

According to the safety hand book, a 60 lb container can hold up to 45 lbs of refrigerant for recovery. This means that it is safe to recover and store up to 45 lbs of refrigerant in a container of this size.

Butane is the refrigerant that requires approval for use by the NYC Fire Department. This is because butane is highly flammable and poses a fire hazard. The NYC Fire Department regulates the use of certain refrigerants to ensure safety and prevent accidents or fires. R-22 and R-12 are commonly used refrigerants, but they do not require approval from the fire department. Carbon dioxide is a natural refrigerant and is considered safe for use.

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 ground fault. This can cause the metal box to become energized, 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.

An automatic purge unit is required for refrigerating systems operating below atmospheric pressure because these systems are more prone to leaks and contaminants entering the system. Operating below atmospheric pressure can cause air and moisture to enter the system, which can lead to reduced efficiency and potential damage to the system. Therefore, an automatic purge unit is necessary to remove any non-condensable gases and maintain the proper pressure and purity of the refrigerant in the system.

Orifice plates can be used as a metering device component in a centrifugal system. In addition to this, the vessel in which they are contained can also serve as an economizer. An economizer is a device that helps in improving the efficiency of a system by utilizing waste heat or energy. In this case, the vessel containing the orifice plates can be designed in such a way that it recycles and utilizes the waste heat or energy generated by the system, thereby serving as an economizer.

Direct systems are most likely to leak refrigerant in building spaces that are being cooled. This is because direct systems have direct contact between the refrigerant and the space being cooled, increasing the chances of leaks occurring. In contrast, indirect systems use a secondary fluid to cool the space, reducing the risk of refrigerant leaks. Indirect closed systems further minimize the risk by using a closed loop system, while indirect open systems have a higher chance of refrigerant leaks due to their open design.

A brazed joint is a type of joint created by joining two pieces of metal with a filler metal that has a lower melting point than the base metals. The filler metal is heated to its melting point and then flows into the joint, creating a strong bond. A brazed joint is known for its ability to create a gas tight fitting, meaning it forms a seal that prevents the escape or entry of gases. This is why "gas tight fitting" is the most correct way to describe a brazed joint.

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

The most common metering device used today in a reciprocating commercial refrigeration system over 3 tons is the thermostatic expansion valve. This valve is preferred because it provides precise control of the refrigerant flow into the evaporator based on the temperature and pressure conditions. It ensures that the right amount of refrigerant is supplied to the evaporator, leading to efficient cooling and preventing the risk of flooding or starving the evaporator. The thermostatic expansion valve also allows for adjustments to be made based on the load requirements, making it a versatile and reliable choice for commercial refrigeration systems.

The correct answer is "ALL OF THE ABOVE". R-11 and R-123 refrigerants are oxygen depleting, meaning they reduce the amount of oxygen available in the air. They are also heavier than air, which means they tend to sink and accumulate at lower levels. Additionally, R-11 and R-123 are classified as Class-1 and Class-2 substances by the Environmental Protection Agency (EPA), indicating their potential for causing harm to human health and the environment.

Adjusting the impeller inlet guide pre-rotation vanes is the most likely action to achieve capacity control in a centrifugal compressor. The impeller inlet guide pre-rotation vanes control the flow of gas into the impeller, which in turn affects the compressor's capacity. By adjusting these vanes, the operator can regulate the amount of gas entering the compressor and therefore control its capacity. This allows the operator to match the compressor's output to the required demand, ensuring efficient operation.

Using warm water helps to increase the release rate of refrigerant from the drum when charging an R-12 reciprocating refrigeration system. However, the water temperature should not exceed 90°F. Temperatures higher than this could potentially cause the refrigerant to vaporize too quickly, leading to inefficient charging and potential damage to the system.

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 plate, which controls the flow rate of the refrigerant. The greater the pressure difference, the higher the flow rate of the refrigerant. Therefore, the difference in pressure between the high and low sides is the determining factor for the amount of refrigerant that flows through the orifice plate.

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 important to handle and store ammonia with caution to prevent any accidents or harm to individuals.

A non-positive displacement pump is a type of pump that does not trap and move a fixed amount of fluid with each cycle. Instead, it uses centrifugal force to move the fluid through the pump. A centrifugal pump works by converting rotational energy from a motor into kinetic energy in the liquid being pumped. This kinetic energy then creates pressure and pushes the fluid out of the pump. Therefore, a centrifugal pump is considered a non-positive displacement pump.

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, and reducing the resistance by 1/2 would result in a doubling of the current. Therefore, the power output of the motor would increase by a factor of 2.

The TEV diaphragm is made of metal because it needs to be strong and durable to withstand the pressure and temperature variations in the system. Metal diaphragms are commonly used in industrial applications where they can handle high pressures and provide long-lasting performance. Rubber, plastic, and graphite diaphragms are not as suitable for this purpose as they may not have the necessary strength or resistance to the conditions in which the TEV operates.

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

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 stream before it is discharged from the cooling tower. If these plates are clogged, they will not be able to effectively remove the water droplets, leading to a higher temperature in the water being returned to the 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 cooling tower uses the process of evaporation to remove heat from the building. As the water in the cooling tower evaporates, it absorbs heat from the building, thereby cooling the building. This heat is then released into the atmosphere as the water vaporizes, thus rejecting the heat from the building.

The correct answer is "WATTS = VOLTS X AMPS X POWER FACTOR". In a refrigeration plant, the true power consumption can be determined by multiplying the voltage (V) by the current (A) and the power factor. The power factor represents the efficiency of the motor in converting electrical power to mechanical power. Multiplying all three values together gives the power consumption in watts.

The correct answer is "ACCORDING TO DESIGN PRESSURE." When installing a pressure relief valve on a reciprocating compressor using R-12, it is typically set according to the design pressure. This means that the valve is adjusted to open and relieve pressure when it reaches the maximum pressure level that the compressor was designed to handle. Setting the relief valve according to the design pressure helps to ensure the safe operation of the compressor and prevent any potential damage or accidents that could occur if the pressure exceeds the design limits.

To check if a thermometer is working properly, you would touch it to a bucket of ice or ice water. This is because when the thermometer is exposed to a cold temperature, it should read close to 0 degrees Celsius or 32 degrees Fahrenheit. By comparing the reading on the thermometer to the expected temperature of the ice or ice water, you can determine if the thermometer is accurate and functioning correctly.

The correct answer is B3. In the ASHRAE safety groups classification, B3 represents refrigerants that are highly flammable and have a higher risk of explosion. This makes them the most dangerous among the given options. A1 and A2 represent non-toxic and non-flammable refrigerants, while B2 represents refrigerants that are toxic but not flammable.

A relief valve is a safety device used in refrigerating systems to prevent overpressure. It is designed to open and release excess pressure when the pressure in the system exceeds a certain threshold, known as the design pressure. Therefore, a RMO (Refrigeration Maintenance Operator) would expect a relief valve to start functioning at the design pressure, as this is the pressure at which it is designed to activate and protect the system. The other options, such as 5% over design pressure or 20% below design pressure, are not accurate because the relief valve should only open when the pressure reaches the design pressure.

The correct answer is A3. In fire safety, the ANSI/ASHRAE refrigerant safety classification that is most dangerous is A3. This classification indicates that the refrigerant is highly flammable, posing a significant risk of fire. It is important to handle and store A3 refrigerants with extreme caution, following proper safety protocols to prevent accidents and ensure the safety of individuals and property.

If the spring in the TEV (Thermal Expansion Valve) were to break, it would result in flooding the evaporator. The TEV is responsible for regulating the flow of refrigerant into the evaporator coil. When the spring breaks, it would cause the valve to remain open, allowing an excessive amount of refrigerant to enter the evaporator. This would lead to an overload of refrigerant in the evaporator, causing it to flood and potentially damage the system.

ASHRAE 15 is the correct answer because it is a safety standard developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). ASHRAE 15 specifically focuses on the safe design, installation, and operation of mechanical refrigeration systems, including those in machine rooms. It provides guidelines and requirements to ensure the safety of personnel working in or around these systems, addressing issues such as ventilation, refrigerant leak detection, and emergency procedures. Therefore, ASHRAE 15 is the appropriate safety standard for machine rooms.

Liquid slugging refers to the presence of liquid in the compressor cylinders, which can cause knocking noises. This can occur due to various reasons such as improper refrigerant charge, liquid refrigerant entering the compressor, or faulty suction line design. In this case, since the RMO is assured that the compressor has no worn parts, the most probable cause of the knocking is liquid slugging.

A cold front causes a sharp drop in Outside Air Temperature (O.A.T.). In this condition, the thermostat will cause the solenoid valve to close. When the solenoid valve closes, it will prevent the flow of refrigerant into the compressor. As a result, the compressor will pump down, meaning it will remove the refrigerant from the system until the pressure reaches a low level. Once the pressure drops to a certain point, the compressor will shut down to prevent damage. Therefore, the correct answer is "CLOSE, THE COMPRESSOR PUMPS DOWN AND SHUTS DOWN ON LOW PRESSURE."

R-22 is not used as a cooling medium in an indirect system because it is a type of hydrochlorofluorocarbon (HCFC) refrigerant that has been phased out due to its harmful effects on the ozone layer. It has been replaced by more environmentally friendly refrigerants such as R-410A. Calcium chloride, glycol, and sodium chloride are commonly used as cooling mediums in indirect systems.

The refrigerant leaving the third compressor would be in the state of highly superheated vapor. This means that the refrigerant has absorbed a significant amount of heat and is in a gaseous state with a temperature above its saturation point. This occurs when the refrigerant has undergone a high level of compression and has been heated beyond its boiling point.

Ammonia has the highest latent heat and refrigeration effect compared to the other refrigerants mentioned. Latent heat refers to the amount of heat absorbed or released during a phase change, such as from liquid to gas. Ammonia has a high latent heat, which means it can absorb a significant amount of heat when it evaporates, making it an efficient refrigerant. Additionally, ammonia has a low boiling point, making it suitable for use in refrigeration systems.

The most likely way to achieve capacity control in a reciprocating compressor is by opening the suction valves with some form of control. By controlling the opening of the suction valves, the amount of gas entering the compressor can be regulated, thus controlling the capacity of the compressor. This allows for precise control and adjustment of the compressor's output based on the demand or process requirements.

Under normal conditions, the cooling water temperature leaving the condenser should be higher than the temperature entering it. This is because the condenser removes heat from the refrigerant, causing the water temperature to increase. Since the cooling water is being supplied at 85°F and leaving at 95°F, it indicates that the condenser is effectively removing heat from the refrigerant. The corresponding compressor head pressure in PSI should be most nearly 213, as it is the only option that aligns with the given information and indicates proper cooling operation.

A pump affects the pressure of a fluid or gas by raising it. When a pump is operated, it creates a pressure difference that forces the fluid or gas to move from an area of lower pressure to an area of higher pressure. This increase in pressure allows the fluid or gas to be transported or used for various purposes, such as in water supply systems, hydraulic systems, or air compression systems. Therefore, the correct answer is "RAISING PRESSURE."

Charging with liquid can cause water in the tubes to freeze. When liquid refrigerant is introduced into the system, it can cause a rapid drop in temperature, leading to the formation of ice. This ice can block the flow of refrigerant and restrict the system's efficiency. Charging with vapor, on the other hand, allows for a gradual increase in temperature, preventing the formation of ice and ensuring proper functioning of the system.

Upon being assigned to a facility during inspection, if there has been a failure to maintain water treatment, the first evidence that would most likely be observed when inspecting the condenser water is an increase in compressor head pressure. This is because the failure to maintain water treatment can lead to the accumulation of contaminants in the condenser water, which can reduce the heat transfer efficiency. As a result, the compressor would have to work harder to maintain the desired pressure, leading to an increase in head pressure.

Excessive superheat at the evaporator outlet can be caused by any of the above options: a starved evaporator, a leak in the system, or a low refrigerant charge. A starved evaporator occurs when there is not enough refrigerant flowing into the evaporator coil, leading to insufficient cooling. A leak in the system can result in a loss of refrigerant, causing a decrease in cooling capacity. A low refrigerant charge means that there is not enough refrigerant in the system, leading to inadequate cooling. Therefore, any of these issues can cause excessive superheat at the evaporator outlet.