# 3e151 B Set Vol 4

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UREs for B set of 3E151 cdcs Vol 4.

• 1.

### In air distributions systems, the three basic categories of fans are

• A.

Backward inclined, airfoil, and forward curve

• B.

• C.

Centrifugal, special design, and axial

• D.

Propeller, tubeaxial, and vaneaxial

C. Centrifugal, special design, and axial
Explanation
The correct answer is centrifugal, special design, and axial. In air distribution systems, centrifugal fans are commonly used due to their ability to generate high airflow and pressure. Special design fans are used for specific applications that require unique features such as explosion-proof or high-temperature resistance. Axial fans are typically used in situations where high airflow rates are needed at low pressure differentials, such as in cooling towers or ventilation systems.

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• 2.

### What are the width and inlet constructions of centrifugal fans?

• A.

SWSI and DWDI

• B.

SWDI and DWSI

• C.

SPST and DPDT

• D.

SPDT and DPST

A. SWSI and DWDI
Explanation
The correct answer is SWSI and DWDI. SWSI stands for Single Width Single Inlet, which means that the fan has a single inlet and a single width. DWDI stands for Double Width Double Inlet, which means that the fan has double inlets and a double width. These terms are used to describe the construction of centrifugal fans and indicate the number of inlets and the width of the fan.

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• 3.

### The purpose of the vanes of a vaneaxial fan is to

• A.

Change the fpm

• B.

Change the cfm

• C.

Increase the torque

• D.

Straighten out the air's spiraling motion

D. Straighten out the air's spiraling motion
Explanation
The purpose of the vanes of a vaneaxial fan is to straighten out the air's spiraling motion. Vaneaxial fans are designed to move large volumes of air at high pressures, and the vanes play a crucial role in achieving this. As the air enters the fan, it tends to spiral due to the rotational motion of the blades. The vanes are strategically placed to counteract this spiraling motion and straighten out the airflow. This ensures more efficient and effective airflow, allowing the fan to function optimally.

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• 4.

### A fan drive is an assembly made up of

• A.

A motor sheave, fan sheave, and connecting belts

• B.

Grooves used to increase and decrease the speed of the fan

• C.

Fixed bores that allow the sheaves to fit the shaft exactly

• D.

Movable discs to increase or decrease the pitch diameter

A. A motor sheave, fan sheave, and connecting belts
Explanation
The correct answer is a motor sheave, fan sheave, and connecting belts. A fan drive is an assembly that consists of these components. The motor sheave is connected to the motor shaft, the fan sheave is connected to the fan shaft, and the connecting belts transmit power from the motor sheave to the fan sheave. By adjusting the size of the sheaves and the tension of the belts, the speed of the fan can be increased or decreased. This allows for control over the airflow and ventilation in a system.

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• 5.

### To prevent needless problems to your heating, ventilation, air conditoner, and refrigeration (HVAC/R) equipment, which items should you check during V-belt inspections?

• A.

Outside diameter

• B.

Proper alignment

• C.

Pitch length

• D.

Belt alignment

B. Proper alignment
Explanation
During V-belt inspections, it is important to check for proper alignment. This ensures that the V-belt is correctly positioned and aligned with the pulleys in the HVAC/R equipment. Proper alignment prevents unnecessary wear and tear on the belt, reduces friction, and ensures efficient functioning of the equipment. Checking the outside diameter, pitch length, and belt alignment are also important aspects of V-belt inspections, but the most crucial one is ensuring proper alignment.

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• 6.

### The most common size of V-belts used in HVAC systems are

• A.

1L, 2L, and 3L

• B.

3L, 4L, and 5L

• C.

A through D

• D.

A and B

C. A through D
Explanation
The correct answer is A through D. This means that the most common size of V-belts used in HVAC systems can vary and include sizes ranging from A to D. The specific size of the V-belt used would depend on the requirements of the HVAC system and the manufacturer's recommendations.

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• 7.

### What is generally the proper tension for the top side of fan belts?

• A.

1/2 to 1 inch deflection

• B.

1/2 to 1 1/2 inch deflection

• C.

3/4 to 1 1/4 inch deflection

• D.

3/4 to 1 3/4 inch deflection

A. 1/2 to 1 inch deflection
Explanation
The proper tension for the top side of fan belts is generally 1/2 to 1 inch deflection.

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• 8.

### A single-duct system become a low-pressure reheat system when

• A.

A higher-pressure duct design and pressure reduction devices are used to permit system balancing

• B.

Heating coils are inserted into the duct system downstream of the cooling coils

• C.

The system responds to only one set of space conditions

• D.

Excess air is dumped into a return-air ceiling plenum

B. Heating coils are inserted into the duct system downstream of the cooling coils
Explanation
When heating coils are inserted into the duct system downstream of the cooling coils, it means that the system has the capability to provide both cooling and heating functions. This is because the cooling coils are located before the heating coils in the airflow path. By having this setup, the system can adjust the temperature of the air as needed, making it a low-pressure reheat system.

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• 9.

### The individual zone or space control is provided in an indution system by

• A.

Heating and secondary airstream

• B.

Careful analysis of the system

• C.

The low-pressure reheat coils

• D.

Inducting the sir

A. Heating and secondary airstream
Explanation
In an induction system, individual zone or space control is achieved by using heating and secondary airstream. This means that the system is designed in such a way that each zone or space can be controlled separately by adjusting the temperature of the heating and secondary airstream. This allows for customized comfort levels in different areas of the space, providing more flexibility and efficiency in heating and cooling. Careful analysis of the system is also important to ensure that the design and implementation of the heating and secondary airstream is done correctly. The low-pressure reheat coils and inducting the air are not directly related to providing individual zone or space control in an induction system.

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• 10.

### Which multiple-path system uses a mixing valve to control zone temperature by mixing warm and cold air in proper proportion?

• A.

Multizone

• B.

Dual-duct

• C.

Dual-reheat

• D.

Variable-air-volume

B. Dual-duct
Explanation
The correct answer for this question is dual-duct. In a dual-duct system, a mixing valve is used to control the temperature in different zones by blending warm and cold air in the correct proportion. This allows for precise temperature control in each zone, ensuring optimal comfort for occupants.

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• 11.

### What is one way to reduce energy costs if a dual-duct system with no cooling load?

• A.

Replace existing boxes with high-pressure boxes

• B.

Operate the system as a single-zone

• C.

Operate the system as a multizone

• D.

Eliminate the return-air fan

B. Operate the system as a single-zone
Explanation
Operating the system as a single-zone can help reduce energy costs in a dual-duct system with no cooling load because it allows for the elimination of unnecessary equipment and reduces the amount of energy required to operate the system. In a single-zone operation, both the supply and return air are mixed together and distributed throughout the building, eliminating the need for separate zones and the associated equipment and energy consumption. This can result in significant energy savings and cost reduction.

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• 12.

### Which multiple-path system meets requirements of the different zones by mixing cold and warm air through dampers at the central HVAC unit?

• A.

High-velocity, dual-duct

• B.

Low-velocity, dual-duct

• C.

Multizone

• D.

Induction

C. Multizone
Explanation
A multizone system is a multiple-path system that meets the requirements of different zones by mixing cold and warm air through dampers at the central HVAC unit. This system allows for individual temperature control in different areas or zones of a building, providing comfort and energy efficiency. Unlike high-velocity or low-velocity dual-duct systems, which use separate ducts for cold and warm air, a multizone system uses dampers to mix the air, making it a suitable choice for meeting the different temperature needs of various zones. Induction systems, on the other hand, use a combination of primary air and induced air to condition the space, which is not the case in this scenario.

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• 13.

### The supply pressure loss data for equipment used in piping systems normally come from

• A.

Manufacturers

• B.

System designers

• C.

HVAC/R technicians

• D.

A. Manufacturers
Explanation
Manufacturers provide the supply pressure loss data for equipment used in piping systems. They have the necessary knowledge and expertise about their products to accurately determine the pressure loss associated with their equipment. System designers and HVAC/R technicians may also have some knowledge about pressure loss, but manufacturers are the primary source for this information as they design and produce the equipment. Velocity head pressure is not a source of supply pressure loss data; it is a term used to calculate the pressure loss in a piping system due to fluid velocity.

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• 14.

• A.

Pressure in psi being pumped representing system resistance that must be overcome

• B.

Pressure due to the weight of the fluid above the point pf measurement

• C.

Sum of the lift and velocity head at the pump

• D.

B. Pressure due to the weight of the fluid above the point pf measurement
Explanation
Static head refers to the pressure due to the weight of the fluid above the point of measurement. It represents the force exerted by the fluid column on the measuring point, resulting from the gravitational pull. This pressure is independent of the pump and is solely determined by the height of the fluid column.

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• 15.

### How many intakes does the single-suction pump impeller have?

• A.

One

• B.

Two

• C.

Three

• D.

Four

A. One
Explanation
The single-suction pump impeller has only one intake. This means that there is only one opening or inlet through which the fluid is drawn into the impeller for pumping. Having only one intake allows for a more streamlined and efficient flow of the fluid, as it is directed towards a single point.

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• 16.

### Which type pump casing collects water from the impeller and discharges it parallel to the

• A.

Multiple

• B.

Volute

• C.

Diffuser

• D.

Single

C. Diffuser
Explanation
A pump casing collects water from the impeller and discharges it parallel to the diffuser. The diffuser is a component in a pump that helps to increase the pressure of the fluid being pumped by gradually expanding the flow area. This allows for a more efficient and smooth flow of water, reducing turbulence and increasing the overall performance of the pump. Therefore, the diffuser is the correct answer in this case.

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• 17.

### Some leakage at the packing gland of a pump is needed to

• A.

Equalize the pressure on the two sides of the seal

• B.

Seal undesirable leakage to the stuffing box

• C.

Allow the coupling halves to be disconnected

• D.

Lubricate and cool the area between the material and shaft

D. Lubricate and cool the area between the material and shaft
Explanation
The leakage at the packing gland of a pump is needed to lubricate and cool the area between the material and shaft. This is because the packing gland creates a seal around the shaft to prevent leakage, but a small amount of leakage is necessary to ensure that the area between the material being pumped and the shaft is properly lubricated and cooled. This helps to prevent friction and heat buildup, which can damage the pump and reduce its efficiency.

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• 18.

### Pumps with mechanical seals

• A.

Can be run dry, depending on the ambient temperature

• B.

Can be run dry, depending on the internal pressure

• C.

Must not be run dry

• D.

Must be run dry

C. Must not be run dry
Explanation
Pumps with mechanical seals must not be run dry because the seals require the presence of fluid to maintain lubrication and prevent overheating. Running the pump without any fluid can lead to damage or failure of the seals, causing leaks and potential damage to the pump itself. Therefore, it is important to ensure that these types of pumps are always operated with sufficient fluid to prevent dry running.

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• 19.

### Destructive pitting and wearing of a pump impeller and casing as well as noise and vibration can be caused

• A.

Cavitation

• B.

Friction loss

• C.

Stratification

• D.

Flow coefficient

A. Cavitation
Explanation
Cavitation is the correct answer because it refers to the formation of vapor bubbles in a liquid due to low pressure, which then collapse and cause damage to the impeller and casing of a pump. This phenomenon can also result in noise and vibration. Friction loss, stratification, and flow coefficient do not directly cause these issues.

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• 20.

### What is normally the cause of vortex in a piping system?

• A.

Undersized piping

• B.

Too many fittings

• C.

Location of the pump

• D.

Configuration of the piping system

D. Configuration of the piping system
Explanation
The configuration of the piping system refers to the layout and design of the pipes, including the angles, bends, and connections. A vortex in a piping system is typically caused by the improper configuration of the pipes, which leads to the formation of swirling or turbulent flow patterns. This can disrupt the smooth flow of fluid and cause issues such as pressure drops, cavitation, or even damage to the system. Therefore, it is important to ensure that the piping system is properly designed and configured to avoid vortex formation.

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• 21.

### What do manufacturers use to show how pumps respond under different operating condidtions?

• A.

Curves of system pressure changes for different altitudes

• B.

Curves of the temperature and pressure limitations

• C.

A graph of net positive suction pressure head curves

• D.

A performance curve graph

D. A performance curve graph
Explanation
Manufacturers use a performance curve graph to show how pumps respond under different operating conditions. This graph represents the relationship between the pump's flow rate and the head it can generate. It provides valuable information about the pump's efficiency, power consumption, and operating range. By analyzing the performance curve, manufacturers can determine the pump's suitability for specific applications and make informed decisions about its operation and maintenance.

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• 22.

### After each major repair to a pump or when there is an indication that the system flow is not correct, what do you check?

• A.

Pump performance

• B.

Mechanical seals

• C.

Stuffing box

• D.

Bearings

A. Pump performance
Explanation
After each major repair to a pump or when there is an indication that the system flow is not correct, it is important to check the pump performance. This involves evaluating various aspects such as the flow rate, pressure, efficiency, and power consumption of the pump. By checking the pump performance, any issues or abnormalities can be identified and addressed, ensuring that the pump is functioning optimally and the system flow is correct.

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• 23.

### What is the maximum allowable working pressure for low-pressure heating boilers with a maximum temperature limitations of 250*F?

• A.

140 psi

• B.

160 psi

• C.

180 psi

• D.

200 psi

B. 160 psi
Explanation
The maximum allowable working pressure for low-pressure heating boilers with a maximum temperature limitation of 250Â°F is 160 psi. This means that the boiler can safely operate at a pressure of up to 160 pounds per square inch without risking damage or failure. It is important to adhere to these pressure limitations to ensure the safety and efficiency of the heating system.

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• 24.

### What is the usual pressure or medium-pressure heating when the usual design supply temperature is approximately 250*F to 350*F?

• A.

140 psi

• B.

150 psi

• C.

160 psi

• D.

180 psi

B. 150 psi
Explanation
The usual pressure for medium-pressure heating is typically around 150 psi when the design supply temperature ranges from approximately 250*F to 350*F. This pressure level is considered suitable for maintaining the desired temperature range in the heating system.

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• 25.

### What is the maximum allowable working pressure for high-pressure heating boilers with a maximum temperature limitation of 450*F?

• A.

180 psi

• B.

200 psi

• C.

250 psi

• D.

300 psi

D. 300 psi
Explanation
High-pressure heating boilers with a maximum temperature limitation of 450Â°F have a maximum allowable working pressure of 300 psi. This means that the boiler can safely operate at a pressure of up to 300 pounds per square inch without risking any damage or failure. It is important to adhere to this pressure limit to ensure the safety and proper functioning of the boiler system.

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• 26.

### What would be the acceptable temperature and pressure of a chilled-water supply system, without an antifreeze additive?

• A.

58*F and less than 125 psi

• B.

58*F and greater that 125 psi

• C.

48*F and less that 125 psi

• D.

48*F and greater that 125 psi

C. 48*F and less that 125 psi
Explanation
The acceptable temperature for a chilled-water supply system without an antifreeze additive is 48Â°F. This is because a lower temperature helps to prevent the growth of bacteria and other microorganisms in the water. The acceptable pressure should be less than 125 psi, as a higher pressure can put stress on the system and potentially cause leaks or damage.

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• 27.

### Which piping system is a continuous run of pipe or tube from the boiler or chilled-water supply connection back to the boiler or chiller?

• A.

Two-pipe reverse-return

• B.

Two-pipe direct-return

• C.

Series-loop

• D.

One-pipe

C. Series-loop
Explanation
A series-loop piping system is a continuous run of pipe or tube from the boiler or chiller back to the boiler or chiller. In this system, the water flows through the loop in a series, meaning that it passes through each terminal unit before returning to the source. This allows for equal distribution of water throughout the system and ensures balanced heating or cooling. The other options, such as two-pipe reverse-return, two-pipe direct-return, and one-pipe, do not necessarily provide a continuous run of pipe or tube back to the source.

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• 28.

### Which hydronic distribution system uses a special diverting tee that creates a pressure drop in the main flow divert a portion of the main flow to the terminal unit?

• A.

One-pipe

• B.

Series-loop

• C.

Two-pipe direct-return

• D.

Two-pipe reverse-return

A. One-pipe
Explanation
A one-pipe hydronic distribution system uses a special diverting tee that creates a pressure drop in the main flow to divert a portion of the main flow to the terminal unit. This system is designed in such a way that the same pipe is used to supply and return the water, hence the name "one-pipe." The diverting tee helps to regulate the flow and ensure that each terminal unit receives an adequate amount of heated or cooled water.

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• 29.

### Since water flow distance from and to the boiler is virtually thesame through any unit, balancing valves require less adjusting on the

• A.

Two-pipe direct return

• B.

Two-pipe reverse return

• C.

One-pipe direct return

• D.

One-pipe reverse return

B. Two-pipe reverse return
Explanation
The two-pipe reverse return system is the correct answer because it allows for more balanced water flow between units. In this system, the water flows in one direction through the supply pipe and returns in the opposite direction through the return pipe. This design helps to equalize the flow distance to and from the boiler, resulting in less need for adjusting balancing valves. The other systems mentioned, such as two-pipe direct return and one-pipe systems, may not provide the same level of balance in water flow.

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• 30.

### Which hydronic distribution system uses a special three-way valve at the inlet to the coil to admit water from either the hot-or-cold   water supply in sequence as required?

• A.

One-pipe

• B.

Two-pipe

• C.

Three-pipe

• D.

Four-pipe

C. Three-pipe
Explanation
A three-pipe hydronic distribution system uses a special three-way valve at the inlet to the coil to admit water from either the hot or cold water supply in sequence as required. This allows for the system to provide both heating and cooling capabilities, as the valve can switch between the two water supplies based on the desired temperature. The three-pipe system is more versatile compared to one-pipe or two-pipe systems, as it allows for greater control over the temperature in different areas of a building.

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• 31.

### When a terminal unit of the hydronic distribution system is provided with two independent water coils, one served by hot water, the other by cold water, this is an example of a

• A.

One-pipe system

• B.

Two-pipe system

• C.

Three-pipe system

• D.

Four-pipe system

D. Four-pipe system
Explanation
When a terminal unit of the hydronic distribution system is provided with two independent water coils, one served by hot water and the other by cold water, this is an example of a four-pipe system. In a four-pipe system, there are separate supply and return pipes for both hot and cold water, allowing for independent control and regulation of the temperature in each coil. This setup provides greater flexibility and control over the heating and cooling of the space compared to a one-pipe, two-pipe, or three-pipe system.

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• 32.

### If air and other gases are not removed from the hydronic piping flow circuit, they may cause

• A.

Excessive air

• B.

Air binding

• C.

Vibration

• D.

Leakage

B. Air binding
Explanation
Air binding occurs when air becomes trapped in the hydronic piping flow circuit and prevents the proper flow of water. This can lead to reduced efficiency and performance of the system, as well as potential damage to the components. It can cause blockages, reduce heat transfer, and create uneven distribution of water throughout the system. Therefore, it is important to remove air and other gases from the hydronic piping flow circuit to prevent air binding and ensure optimal operation.

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• 33.

### All low points on hydronic systems should be equipped with

• A.

Vents

• B.

Drains

• C.

Stutoffs

• D.

Strainers

B. Drains
Explanation
All low points on hydronic systems should be equipped with drains. Drains are necessary to remove any accumulated water or condensation from the system. Without drains, water can build up in low points and cause damage to the system or create an environment for bacterial growth. Therefore, drains are essential to maintain the proper functioning and longevity of hydronic systems.

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• 34.

### When the condensate of a steam system has cooled below the condensing temperature, this is referred to as

• A.

Superheating

• B.

Subcooling

• C.

Saturated vapor

• D.

Enthalpy

B. Subcooling
Explanation
When the condensate of a steam system has cooled below the condensing temperature, it is referred to as subcooling. Subcooling occurs when the temperature of the condensate is lower than its saturation temperature at the given pressure. This can happen when additional cooling is applied to the condensate after it has already reached its saturation point. Subcooling helps to ensure that the condensate remains in a liquid state, which is important for efficient heat transfer and preventing damage to equipment.

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• 35.

### Because it is necessary to keep a steam system in service at all times, what is installed around the automatic temperature control valve?

• A.

Dipped supply piping

• B.

Thermostatic traps

• C.

Steam mains

• D.

A bypass

D. A bypass
Explanation
A bypass is installed around the automatic temperature control valve in order to keep the steam system in service at all times. This bypass allows the steam to flow even when the temperature control valve is closed or not functioning properly. It ensures that there is a continuous supply of steam to the system, preventing any disruptions or downtime.

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• 36.

### Which steam trap reacts to a difference in the temperature between the steam and condensate?

• A.

Mechanical

• B.

Safety relief

• C.

Thermostatic

• D.

Inverted-bucket trap

C. Thermostatic
Explanation
A thermostatic steam trap is designed to react to the temperature difference between the steam and condensate. When the steam cools down and condenses into water, the thermostatic trap senses the temperature change and opens up to allow the condensate to be discharged. Once the steam starts flowing again, the trap closes to prevent the steam from escaping. This type of steam trap is commonly used in systems where the temperature difference between the steam and condensate is significant.

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• 37.

### Which thermostatic trap is not adversely affected by superheated steam?

• A.

Bellows

• B.

Balanced

• C.

Inverted

• D.

Bimetallic

D. Bimetallic
Explanation
The bimetallic thermostatic trap is not adversely affected by superheated steam because it uses a combination of two different metals with different coefficients of thermal expansion. This allows the trap to expand and contract at different rates, ensuring that it can handle the high temperatures of superheated steam without being damaged. The other traps mentioned - bellows, balanced, and inverted - do not have the same ability to withstand superheated steam and may be adversely affected by it.

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• 38.

### When pressure-reducing valves are used in a steam system, what must also be used?

• A.

Relief devices

• B.

Mechanical traps

• C.

Inverted-bucket traps

• D.

Pilot-controlled valves

A. Relief devices
Explanation
When pressure-reducing valves are used in a steam system, relief devices must also be used. This is because pressure-reducing valves only control the pressure in the system, but they do not provide protection against overpressure. Relief devices, such as safety valves or pressure relief valves, are necessary to prevent the pressure from exceeding safe limits and causing damage to the system or equipment. These devices automatically open and release excess pressure when it reaches a certain threshold, ensuring the safety and integrity of the steam system.

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• 39.

### In hydronic heating and cooling units, radiators are rated in terms of the square feet of

• A.

Steam flow

• B.

Water flow

• C.

British thermal units (BTU)

• D.

Explanation
In hydronic heating and cooling units, radiators are rated in terms of equivalent direct radiation (EDR). EDR is a measurement that represents the amount of heat output that a radiator can provide. It takes into account factors such as the size of the radiator, the surface area of the fins, and the type of metal used. By using EDR ratings, it becomes easier to determine the appropriate size of radiator needed for a specific space, ensuring efficient heating and cooling.

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• 40.

• A.

Location

• B.

Efficiency

• C.

Position

• D.

Capacity and configuration

D. Capacity and configuration
Explanation
The square feet of equivalent direct radiation (EDR) of a radiator depends on its capacity and configuration. Capacity refers to the amount of heat that the radiator can produce, while configuration refers to the design and arrangement of the radiator's heating elements. Both factors play a crucial role in determining the EDR of a radiator. The capacity of the radiator determines the amount of heat it can emit, while the configuration affects the distribution and efficiency of the heat. Therefore, the EDR of a radiator is influenced by its capacity and configuration.

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• 41.

### The primary types of baseboard units are

• A.

Water and steam

• B.

Large tube, small tube, and convector

• C.

Wall mounted, recessed, and concealed

• D.

Explanation
The primary types of baseboard units are radiant, radiant-convector, and finned-tube. These types of baseboard units are commonly used for heating purposes. Radiant baseboard units use electric heating elements or hot water to radiate heat into the room. Radiant-convector baseboard units combine radiant heat with convection heat, using a fan to circulate warm air. Finned-tube baseboard units have metal fins that increase the surface area and enhance heat transfer. These different types of baseboard units provide various options for heating systems depending on the specific needs and preferences of the user.

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• 42.

### Hot-water panel heaters include the

• A.

Ceiling, wall, and floor panel types

• B.

Hot-water, steam, and electrical types

• C.

Large-tube, small-tube, and convector types

• D.

A. Ceiling, wall, and floor panel types
Explanation
Hot-water panel heaters are available in different types including ceiling, wall, and floor panels. These types of panel heaters are designed to heat a room by using hot water as the heat source. The ceiling, wall, and floor panels are all effective in distributing heat evenly throughout the room. Each type of panel heater has its own advantages and can be suitable for different spaces depending on the layout and requirements.

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• 43.

### When lubricating unit ventilator fan and motor bearings, you should?

• A.

Disconnect the motor

• B.

Remove the squirrel cage

• C.

Check the temperature drop

• D.

Explanation
When lubricating unit ventilator fan and motor bearings, it is important to follow the manufacturer's recommendations. The manufacturer's recommendations will provide specific instructions on the type of lubricant to use, the frequency of lubrication, and any other important considerations. Following these recommendations ensures that the bearings are properly lubricated, which helps to reduce friction and wear, extend the lifespan of the bearings, and maintain the efficiency and performance of the unit ventilator fan and motor.

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• 44.

### Which duct system terminal unit is supplied with both hot and cold air?

• A.

Induction

• B.

Dual-duct

• C.

Single-duct

• D.

Variable-air-volume

B. Dual-duct
Explanation
A dual-duct system terminal unit is supplied with both hot and cold air. This system is designed to provide separate ducts for hot and cold air, allowing for precise control over the temperature in a space. By supplying both hot and cold air, the dual-duct system can quickly adjust the temperature to meet the desired comfort level. This makes it an efficient and effective solution for heating and cooling in buildings.

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• 45.

### Because the pressure in the hot and cold ducts of a dual-duct terminal may vary over a wide pressure range due to the demand for the hot and cold air varying throughout the building, it is important to have

• A.

An inlet vane

• B.

A sound baffle

• C.

A pneumatic motor

• D.

An automatic airflow control device

D. An automatic airflow control device
Explanation
In a dual-duct terminal system, the pressure in the hot and cold ducts can vary significantly due to the varying demand for hot and cold air in different parts of the building. To ensure proper control and regulation of the airflow in such a system, it is important to have an automatic airflow control device. This device can adjust the airflow based on the demand, maintaining a balanced and consistent airflow in both the hot and cold ducts. It helps in maintaining a comfortable indoor environment and efficient operation of the system.

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• 46.

### Which duct system terminal unit has a manually operated damper that is adjusted when the system is initially balanced and then left in that position to maintain constant airflow?

• A.

Dual-duct

• B.

Induction

• C.

Single-duct

• D.

Variable-air-volume

D. Variable-air-volume
Explanation
A variable-air-volume (VAV) duct system terminal unit has a manually operated damper that is adjusted during the initial balancing of the system. Once the desired airflow is achieved, the damper is left in that position to maintain a constant airflow. This type of terminal unit is commonly used in HVAC systems where the airflow needs to be adjusted based on the cooling or heating demands of different zones or rooms. By maintaining a constant airflow, the VAV system ensures efficient and comfortable operation.

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• 47.

### How does the induction unit circulate air from the the room through the coil?

• A.

A fan is used

• B.

It does not circulate

• C.

It induces air through the coil

• D.

Air from a central unit is supplied

C. It induces air through the coil
Explanation
The induction unit circulates air from the room through the coil by inducing air through the coil. This means that the unit uses a process to draw or pull air from the room into the coil, allowing it to circulate and be treated or conditioned. The induction unit does not rely on a fan or the supply of air from a central unit to circulate the air.

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• 48.

### Normally, the basic central station HVAC equipment in the air/hydronic unit is located?

• A.

In each separate zone

• B.

Inside the conditioned space

• C.

Outside the conditioned space

• D.

With the heating and refrigeration equipment

C. Outside the conditioned space
Explanation
The basic central station HVAC equipment is typically located outside the conditioned space. This is because the equipment, such as the heating and refrigeration units, needs to be housed in a separate area to prevent noise and heat transfer into the conditioned space. Additionally, locating the equipment outside allows for easier access for maintenance and repairs.

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• 49.

### In a central station unit, heat recovery equipment may be placed between the outdoor intake and coils, and in mild climates, may replace the

• A.

Heating coil

• B.

Preheat coil

• C.

Cooling coil

• D.

Humidifier

B. Preheat coil
Explanation
In a central station unit, heat recovery equipment can be placed between the outdoor intake and coils. This equipment is designed to recover and reuse heat from the outgoing air to preheat the incoming air. In mild climates, where the need for heating is minimal, the heat recovery equipment may replace the preheat coil. This means that instead of using a separate preheat coil to warm up the incoming air, the heat recovery equipment efficiently utilizes the heat from the outgoing air to achieve the same effect.

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• 50.

### The use of a retrun-air fan in central station unit is optional but generally is essential for proper operation of

• A.

Heat recovery

• B.

Larger systems

• C.

Smaller systems

• D.

Dehumidification

B. Larger systems
Explanation
A return-air fan is optional but generally essential for larger systems in a central station unit. This is because larger systems require more airflow to properly circulate and condition the air in the space. The return-air fan helps to pull the air back into the unit, allowing for efficient operation and better control of temperature and humidity levels. In smaller systems, the airflow may be sufficient without the need for a return-air fan. However, in larger systems, the use of a return-air fan is recommended to ensure proper operation and performance.

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• Current Version
• Mar 22, 2023
Quiz Edited by
ProProfs Editorial Team
• Mar 20, 2012
Quiz Created by
Enorab

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