# Maryland Engineer 3rd Class Test

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Quizzes Created: 1 | Total Attempts: 327
Questions: 83 | Attempts: 327

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• 1.

### The warm air distribution system that is usually located along the center line of the building is the:

• A.

Balanced supply/return

• B.

Extended plenum

• C.

Perimeter loop

• D.

B. Extended plenum
Explanation
The warm air distribution system that is usually located along the center line of the building is called an extended plenum. This system is designed to evenly distribute warm air throughout the building by using a main duct that runs along the center line and branches off into smaller ducts that supply air to different areas. The extended plenum design helps to maintain a balanced airflow and temperature throughout the building.

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• 2.

### (Fill in the Blank) Seamus needs to check the steam system at the point where the pressure is the highest. He should check _____ where the heat is ___?

• A.

• B.

Boiler; removed

• C.

• D.

Explanation
Seamus needs to check the steam system at the point where the pressure is the highest. He should check the boiler where the heat is added.

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• 3.

### Latent heat of fusion is the amount of heat required for a substance to change from a  ____

• A.

Gas to a liquid

• B.

Liquid to a gas

• C.

Solid to a gas

• D.

Solid to a liquid

D. Solid to a liquid
Explanation
The correct answer is solid to a liquid. Latent heat of fusion refers to the amount of heat energy required to change a substance from its solid state to its liquid state, without changing its temperature. This is because during this phase transition, the substance absorbs heat energy to overcome the intermolecular forces holding its particles together in a solid lattice structure.

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• 4.

### One of the largest potential energy wasters in a steam distribution system is:

• A.

Leaking steam traps

• B.

Faulty throttling valves

• C.

Air in the system

• D.

Uninsulated condensate lines

A. Leaking steam traps
Explanation
Leaking steam traps can be a significant potential energy waster in a steam distribution system. Steam traps are used to remove condensate from the steam system, but when they leak, they allow live steam to escape. This leads to a loss of energy and can result in higher energy costs. By identifying and repairing these leaks, the system can operate more efficiently and reduce energy waste.

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• 5.

### You have been told that the cost of heating oil is increasing by 4%. If the current cost of oil is \$1.04, the new price will be:

• A.

\$1.43

• B.

\$1.16

• C.

1.08

• D.

1.04

C. 1.08
Explanation
The cost of heating oil is increasing by 4% of the current price. To find the new price, we need to add 4% of \$1.04 to \$1.04. 4% of \$1.04 is \$0.0416. Adding this to \$1.04 gives us \$1.0816, which can be rounded to \$1.08. Therefore, the new price of heating oil will be \$1.08.

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• 6.

### Boiler furnace explosions are likely to occur for all of the following reasons except?

• A.

A weak pilot flame

• B.

Low fuel pressure

• C.

Insufficient combustion air

• D.

Insufficient purge of the furnace before startup

B. Low fuel pressure
Explanation
Boiler furnace explosions are likely to occur due to various reasons such as a weak pilot flame, insufficient combustion air, and insufficient purge of the furnace before startup. However, low fuel pressure is not a likely cause of boiler furnace explosions. Low fuel pressure may result in inefficient combustion or difficulty in starting the furnace, but it is less likely to cause a sudden explosion.

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• 7.

### All of the following boiler fitting are required on hot water heating boilers except?

• A.

A pressure or altitude gauge

• B.

A safety relief valve

• C.

A shut-off valve

• D.

A water gauge glass and column

D. A water gauge glass and column
Explanation
A water gauge glass and column is not required on hot water heating boilers. This is because hot water heating boilers do not require a visual indicator to measure the water level, unlike steam boilers. The other options listed (pressure or altitude gauge, safety relief valve, shut-off valve) are all necessary components for the safe and efficient operation of hot water heating boilers.

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• 8.

### CBS company burns hydrocarbons to generate electricity for its operations. What are the two most common byproducts of hydrocarbon combustion?

• A.

Carbon monoxide and sulfer

• B.

Carbon monoxide and water

• C.

Carbon dioxide and sulfur

• D.

Carbon dioxide and water

D. Carbon dioxide and water
Explanation
When hydrocarbons are burned, the two most common byproducts are carbon dioxide (CO2) and water (H2O). This occurs because the combustion reaction combines the carbon atoms in the hydrocarbons with oxygen from the air, forming carbon dioxide, and the hydrogen atoms combine with oxygen to form water. Carbon monoxide (CO) and sulfur (S) are not the most common byproducts of hydrocarbon combustion.

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• 9.

### All of the following could cause a VAV-belt to fray, crack, or wear except?

• A.

Loose belt tension

• B.

Incorrect pulley sizes

• C.

Pulleys out of alignment

• D.

Shafts not parallel

B. Incorrect pulley sizes
Explanation
Incorrect pulley sizes could cause a VAV-belt to fray, crack, or wear. When the pulley sizes are not appropriate, it can lead to excessive tension or slack in the belt, causing it to wear out quickly. This can result in fraying, cracking, or overall damage to the belt. On the other hand, loose belt tension, pulleys out of alignment, and shafts not parallel can also contribute to belt wear and damage, but incorrect pulley sizes specifically focus on the size mismatch, making it the exception in this scenario.

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• 10.

### In all steam heating systems, the vertical steam supply pipes are called?

• A.

Riser

• B.

Returns

• C.

Upfeeds

• D.

Wet lines

A. Riser
Explanation
In steam heating systems, the vertical steam supply pipes are referred to as risers. These pipes carry the steam from the boiler to the upper floors or radiators of a building. The term "riser" is used because these pipes rise vertically, allowing the steam to flow upwards and distribute heat throughout the system.

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• 11.

### If a pump sounds like it is pumping gravel, the most likely problem is?

• A.

Lack of balance

• B.

Worn bearings

• C.

Loose couplings

• D.

Cavitation

D. Cavitation
Explanation
Cavitation is the most likely problem when a pump sounds like it is pumping gravel. Cavitation occurs when the pressure in the pump drops to a level where the liquid being pumped vaporizes and forms bubbles. These bubbles then collapse violently, causing a noise similar to pumping gravel. Cavitation can damage the pump and reduce its efficiency, so it is important to address this issue promptly.

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• 12.

### A thermocouple used to detect the presence of a gas flame consists of?

• A.

An infrared ray-emitting device

• B.

A rod extending into the flame

• C.

An ultraviolet ray-emitting device

• D.

Two wires of dissimilar metal welded together

D. Two wires of dissimilar metal welded together
Explanation
A thermocouple used to detect the presence of a gas flame consists of two wires of dissimilar metal welded together. When the flame is present, it heats up the junction of the two metals, creating a temperature difference. This temperature difference generates a small electric voltage, known as the thermoelectric effect. This voltage is then used to detect the presence of the flame and can be used to control the gas supply accordingly. The infrared and ultraviolet ray-emitting devices mentioned are not directly related to the functioning of a thermocouple in detecting a gas flame.

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• 13.

### The lowest temperature at which condensation can be prevented in the flu gas passages of a hot water heating boiler is

• A.

170°

• B.

190°

• C.

210°

• D.

130°

D. 130°
Explanation
The lowest temperature at which condensation can be prevented in the flu gas passages of a hot water heating boiler is 130°. This means that if the temperature of the flu gas falls below 130°, condensation will occur in the passages. Condensation can be problematic as it can lead to corrosion and damage to the boiler. Therefore, it is important to maintain the flu gas temperature above 130° to prevent condensation.

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• 14.

### The device that ensures that steam pressure will not force the boiler water back into the return line is a?

• A.

Condensate trap

• B.

Direct feed pump

• C.

Hartford loop

• D.

Pressure regulator

C. Hartford loop
Explanation
A Hartford loop is a device that ensures that steam pressure does not force the boiler water back into the return line. It is a piping arrangement that creates a loop in the steam supply and return lines, allowing condensate to collect and drain back into the boiler. This prevents water hammer and damage to the boiler by keeping the water separate from the steam.

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• 15.

### Two types of electric boilers are the electrode and the?

• A.

Immersion

• B.

Modified Scotch

• C.

Steel plate

• D.

Tubular

A. Immersion
Explanation
The correct answer is "immersion" because it is mentioned as one of the two types of electric boilers in the question. The other type mentioned is the electrode, indicating that "immersion" is the missing option.

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• 16.

### A packing-type seal is designed to leak a small amount of liquid through the packing to?

• A.

Lubricate and cool the packing

• B.

Relieve system pressure

• C.

Check temperature of fluids

• D.

Keep air out of the system

A. Lubricate and cool the packing
Explanation
A packing-type seal is designed to leak a small amount of liquid through the packing to lubricate and cool the packing. This is important because the packing, which is used to create a seal between moving parts, can generate heat and friction during operation. By allowing a small amount of liquid to leak through the packing, it helps to reduce friction and heat buildup, ensuring the longevity and efficiency of the seal.

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• 17.

### The directions on a bottle of cleaning fluid call for an 8:1 ration of water to full-strength fluid. How many gallons of ready-to-use solution will one quart of full-strength fluid yield? (1 gallon = 4 quarts)

• A.

2.0 gal

• B.

2.25 gal

• C.

8.25 gal

• D.

9.0 gal

C. 8.25 gal
Explanation
One quart of full-strength fluid is equivalent to 1/4 of a gallon. According to the directions, the ratio of water to full-strength fluid is 8:1. Therefore, for every 8 parts of water, there is 1 part of full-strength fluid. To find the total amount of ready-to-use solution, we need to add the amount of water and full-strength fluid together. Since the ratio is 8:1, we can divide the total amount of liquid by 9 (8 parts water + 1 part full-strength fluid). 1/4 gallon divided by 9 is approximately 0.0278 gallons. Therefore, one quart of full-strength fluid will yield approximately 0.0278 gallons of ready-to-use solution, which is equivalent to 8.25 gallons.

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• 18.

### The greatest benefit of the dry method of laying up a boiler is it?

• A.

Prevents freezing

• B.

Minimizes corrosion

• C.

Minimizes oxidation

• D.

Eliminates off-season leaking

A. Prevents freezing
Explanation
The dry method of laying up a boiler prevents freezing. This is because during the dry method, all the water is drained from the boiler, leaving no liquid to freeze and potentially cause damage to the system. By preventing freezing, the dry method helps to ensure the longevity and proper functioning of the boiler.

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• 19.

### The control used on gas and oil fired heating boilers to provide for proper sequencing of the combustion controls during the startup and shutdown is the?

• A.

Limit control

• B.

Capacity control

• C.

Programming control

• D.

Safety control

C. Programming control
Explanation
The programming control is used on gas and oil fired heating boilers to ensure proper sequencing of the combustion controls during startup and shutdown. This control is responsible for programming and coordinating the various functions and operations of the boiler system, ensuring that the combustion controls are activated in the correct order and at the appropriate times. It helps in optimizing the efficiency and safety of the boiler by controlling the fuel supply, ignition, and shutdown processes.

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• 20.

### A volute is part of a?

• A.

Centrifugal pump

• B.

Gear pump

• C.

Hose pump

• D.

Plunger pump

A. Centrifugal pump
Explanation
A volute is a part of a centrifugal pump. It is a curved casing that converts the kinetic energy of the fluid into pressure energy. The volute is responsible for directing the flow of fluid from the impeller to the discharge pipe. It helps to increase the efficiency of the pump by reducing turbulence and increasing the pressure of the fluid. In centrifugal pumps, the volute is a crucial component that plays a significant role in the pump's overall performance.

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• 21.

### Some steam heating systems operate under a vacuum in order to?

• A.

Prevent steam leaks

• B.

Use steam with a temperature above 212°f

• C.

Use steam with a temperature below 212°f

• D.

Prevent air from entering the steam heating system

C. Use steam with a temperature below 212°f
Explanation
Steam heating systems that operate under a vacuum are designed to use steam with a temperature below 212°F. This is because when steam is at a lower temperature, it requires less energy to produce and maintain, making it more efficient and cost-effective for heating purposes. Additionally, operating under a vacuum helps to prevent air from entering the steam heating system, which can cause corrosion and other issues.

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• 22.

### The amount of heat necessary to convert 100 lbs of ice at 32°f to water at 132°f is

• A.

10,000 BTU

• B.

24,400 BTU

• C.

14,400 BTU

• D.

10,050 BTU

A. 10,000 BTU
Explanation
To convert 100 lbs of ice at 32°F to water at 132°F, we need to consider two processes: first, we need to heat the ice from its initial temperature of 32°F to its melting point of 32°F, and then we need to heat the water from its melting point of 32°F to the final temperature of 132°F. The amount of heat required to heat the ice is given by the formula Q = m * C * ΔT, where Q is the heat energy, m is the mass, C is the specific heat capacity, and ΔT is the change in temperature. Since the ice is already at its melting point, there is no change in temperature, so the heat required to melt the ice is 0. Then, the heat required to heat the water is given by the same formula. The specific heat capacity of water is 1 BTU/lb°F, so the heat required is Q = 100 lbs * 1 BTU/lb°F * (132°F - 32°F) = 10,000 BTU. Therefore, the correct answer is 10,000 BTU.

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• 23.

### The boiler operator should watch at all times for all of the following except?

• A.

Leaks in steam, water, and fuel connections

• B.

Proper fuel air ratio

• C.

Operating pressure and temperatures

• D.

Incoming water quality

D. Incoming water quality
Explanation
The boiler operator should watch at all times for leaks in steam, water, and fuel connections to ensure that there are no potential safety hazards or wastage of resources. They should also monitor the proper fuel air ratio to maintain efficient combustion and prevent any issues related to incomplete or excessive burning. Additionally, the operator needs to keep an eye on operating pressure and temperatures to ensure that they are within safe and optimal limits. However, incoming water quality is not directly related to the operation and performance of the boiler, so it is not necessary for the operator to constantly monitor it.

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• 24.

### One advantage of hydronic heating over steam heating is?

• A.

Condensate returns are smaller

• B.

Less building damage may result from a leak

• C.

Piping pitch or slope is not as critical

• D.

Pressure and temperature are easily controlled

C. Piping pitch or slope is not as critical
Explanation
Hydronic heating has an advantage over steam heating because piping pitch or slope is not as critical. This means that the pipes used for hydronic heating do not need to be installed with a specific slope or pitch in order to function properly. In steam heating systems, the pipes must be installed with a specific slope to ensure that condensate returns to the boiler. However, in hydronic heating systems, the water flows through the pipes without the need for specific slopes, making installation and maintenance easier.

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• 25.

### When steam or hot water is used as the heat source in a secondary warm air heating system, the system may be classified as a?

• A.

Direct-fired boiler

• B.

Fin-coil heat exchanger

• C.

Vertical forced air

• D.

Low-boy air

B. Fin-coil heat exchanger
Explanation
When steam or hot water is used as the heat source in a secondary warm air heating system, the system may be classified as a fin-coil heat exchanger. A fin-coil heat exchanger is a type of heat exchanger that consists of a coil with fins attached to it. The steam or hot water flows through the coil, transferring heat to the fins, which in turn transfer the heat to the air passing over them. This heated air is then distributed throughout the space using a forced air system. The use of a fin-coil heat exchanger allows for efficient heat transfer and effective heating of the air in the secondary warm air heating system.

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• 26.

### Boilers that have hot gases circulation through tubes surrounded by water are called

• A.

Firetube boilers

• B.

High pressure boilers

• C.

Low pressure boilers

• D.

Low-boy air

A. Firetube boilers
Explanation
Firetube boilers are boilers that have hot gases circulating through tubes surrounded by water. This design allows for efficient heat transfer and is commonly used in industrial applications. The hot gases pass through the tubes, heating the water and producing steam. Firetube boilers are known for their compact size, ease of maintenance, and ability to handle high pressure. They are commonly used in power plants, refineries, and other industrial settings where high heat and pressure are required.

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• 27.

### The type of ventilation system that forces fresh air into the building by a fan and moves stale air out through outlets in outside walls or the roof is called?

• A.

Forced air

• B.

Makeup ventilation

• C.

Natural balancing pressure

• D.

Mechanical air intake/natural exhaust

D. Mechanical air intake/natural exhaust
Explanation
The correct answer is mechanical air intake/natural exhaust. This type of ventilation system uses a fan to bring fresh air into the building and allows stale air to exit through outlets in the outside walls or roof. It combines mechanical air intake with natural exhaust to ensure proper air circulation and maintain indoor air quality.

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• 28.

### ( Fill in the blank) A silver spoon placed in hot coffee quickly becomes too hot to handle. The spoon is heated by__?

• A.

Conduction

• B.

Convection

• C.

• D.

None of the above

A. Conduction
Explanation
The silver spoon placed in hot coffee becomes too hot to handle because of conduction. Conduction is the transfer of heat through direct contact between two objects. In this case, the hot coffee transfers its heat energy to the spoon through direct contact, causing the spoon to heat up.

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• 29.

### The uneven expansion of cold metal when subjected to high heat is referred to as?

• A.

Stress fatigue

• B.

Thermal shock

• C.

Conduction cracking

• D.

Metallic heat failure

B. Thermal shock
Explanation
Thermal shock refers to the uneven expansion of cold metal when exposed to high heat. This phenomenon can cause stress and cracking in the metal due to the rapid temperature change. It is a common issue in materials that have low thermal conductivity, leading to differential expansion and contraction. This can result in structural damage and failure, making thermal shock a significant concern in various industries, such as manufacturing and engineering.

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• 30.

### The three fundamentals units of measurement in physical mechanics are?

• A.

Acceleration, time, and mass

• B.

Length, width, and height

• C.

Time, length, and force

• D.

Time, velocity, and mass

C. Time, length, and force
Explanation
The three fundamental units of measurement in physical mechanics are time, length, and force. Time is a fundamental concept in physics as it allows us to measure the duration of events. Length is also essential as it helps us determine the size or distance between objects. Lastly, force is crucial in mechanics as it describes the interaction between objects and their ability to cause acceleration. These three units are fundamental in understanding and analyzing the motion and behavior of objects in the field of physical mechanics.

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• 31.

### The smallest type of expansion tank is the

• A.

Diaphragm expansion tank

• B.

Open expansion tank

• C.

Closed expansion tank

• D.

Conventional expansion tank

A. Diaphragm expansion tank
Explanation
A diaphragm expansion tank is the smallest type of expansion tank. It is designed with a flexible diaphragm that separates the air and water inside the tank. This diaphragm allows for the expansion of water as it heats up, preventing excessive pressure buildup in the system. The compact size of the diaphragm expansion tank makes it ideal for smaller spaces or applications where space is limited.

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• 32.

### The scale on a pressure gauge dial should be graduated with a range up to?

• A.

1 1\2 to 3 times the working pressure

• B.

The maximum working pressure

• C.

5 times the working pressure

• D.

1\2 the working pressure

A. 1 1\2 to 3 times the working pressure
Explanation
The scale on a pressure gauge dial should be graduated with a range up to 1 1/2 to 3 times the working pressure. This is because the pressure gauge needs to have a sufficient range to accurately measure the pressure fluctuations within the system. Graduating the scale with a range that is 1 1/2 to 3 times the working pressure allows for variations in pressure without exceeding the maximum limit of the gauge. This range ensures that the gauge can effectively monitor and display the pressure levels within the desired range.

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• 33.

### Trimming an impeller should result in a?

• A.

Reduction of noise

• B.

Decrease of power consumption

• C.

Improvement of a cavitation problem

• D.

Increase in pump horsepower

B. Decrease of power consumption
Explanation
Trimming an impeller involves removing material from the impeller blades, which can result in a decrease in power consumption. By reducing the weight and size of the impeller, it requires less energy to rotate, resulting in a decrease in power consumption. Trimming can help optimize the impeller's performance and improve the efficiency of the pump system, leading to energy savings.

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• 34.

### The metric to USCS conversion factor for meters to feet is 3.281 Convert 20 meters to feet

• A.

164.0 ft.

• B.

72.9 ft.

• C.

65.6 ft.

• D.

6.1 ft.

C. 65.6 ft.
Explanation
The correct answer is 65.6 ft. To convert meters to feet, we multiply the length in meters by the conversion factor of 3.281. Therefore, 20 meters multiplied by 3.281 equals 65.6 feet.

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• 35.

### All of the following are advantages of radiant heating panels except?

• A.

System changes are easy to make

• B.

Heating elements are out of sight

• C.

Temperature distribution is more even

• D.

Building built on concrete slabs are more comfortable

A. System changes are easy to make
Explanation
Radiant heating panels have several advantages, such as heating elements being out of sight, temperature distribution being more even, and buildings built on concrete slabs being more comfortable. However, the statement that system changes are easy to make is not a correct advantage of radiant heating panels. This suggests that making changes to the system may not be as simple or convenient compared to the other benefits provided by radiant heating panels.

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• 36.

### The expansion tank should be located on the suction side of the pump to?

• A.

Control the loop temperature

• B.

Prevent clogs in the strainer

• C.

Avoid negative pressure in the system

• D.

Avoid excessive pressure in the system

C. Avoid negative pressure in the system
Explanation
The expansion tank should be located on the suction side of the pump to avoid negative pressure in the system. Negative pressure occurs when the pressure in the system drops below atmospheric pressure, which can lead to cavitation and damage to the pump. By placing the expansion tank on the suction side, it helps to maintain a positive pressure in the system and prevents the formation of negative pressure zones.

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• 37.

### Insufficient positive draft could result in all the following except?

• A.

Burner overheatin

• B.

Incomplete combustion

• C.

Dangers to environment for people

• D.

Increased carbon monixide

A. Burner overheatin
Explanation
Insufficient positive draft could result in incomplete combustion, dangers to the environment for people, and increased carbon monoxide. However, it would not result in burner overheating.

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• 38.

### (Fill in the blank) A (n) is formed when two straight lines intersect or cross at a common point

• A.

Angle

• B.

Axis

• C.

Intercept

• D.

Polygon

A. Angle
Explanation
When two straight lines intersect or cross at a common point, they form an angle. An angle is a geometric figure that is formed by two rays with a common endpoint. It is measured in degrees and can range from 0 to 360 degrees. The point of intersection is called the vertex of the angle. Therefore, the correct answer is angle.

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• 39.

### (Fill in the blanks) The CBS low-pressure heating boiler has failed. Without even checking it, the facility manager Todd believes he knows the reason, as the most common cause of such failures is overheating of the ___ surface resulting from a ___ water

• A.

Heating, low

• B.

Heating, high

• C.

Cooling, high

• D.

Cooling, low

A. Heating, low
Explanation
The most common cause of low-pressure heating boiler failures is overheating of the heating surface resulting from low water heating. Todd, the facility manager, believes this is the reason for the CBS boiler failure without even checking it.

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• 40.

### For facilities that require short-term operation where quick warm-up is required, the least responsive type of boiler to use is the

• A.

Tubular boiler

• B.

Electrical boiler

• C.

Firetube boiler

• D.

Watertube boiler

C. Firetube boiler
Explanation
A firetube boiler is the least responsive type of boiler to use in facilities that require short-term operation and quick warm-up. This is because firetube boilers have a large water volume and take longer to heat up compared to other types of boilers.

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• 41.

### The most common type of firetube boiler used for heating large buildings is the?

• A.

Cast-iron

• B.

High pressure

• C.

Modified Scotch

• D.

Modular

C. Modified Scotch
Explanation
A modified Scotch firetube boiler is the most common type of firetube boiler used for heating large buildings. This type of boiler is designed with a large volume of water and a long path for the hot gases to travel, allowing for efficient heat transfer. It is commonly used in heating systems for its reliability, durability, and ability to handle high pressures. The modified Scotch design incorporates improvements and modifications to the traditional Scotch boiler, making it even more suitable for heating large buildings.

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• 42.

### The unit of measurement a compound pressure gauge uses to measure pressures below atmospheric pressure is?

• A.

Inches of mercury

• B.

Inches of water

• C.

Pounds per square inch

• D.

Pounds per square inch gauge

A. Inches of mercury
Explanation
A compound pressure gauge uses inches of mercury as the unit of measurement to measure pressures below atmospheric pressure. This unit is commonly used in applications such as vacuum systems and barometers. Inches of mercury refers to the height of a column of mercury in a tube, which is used to indicate the pressure. As the pressure decreases below atmospheric pressure, the height of the mercury column also decreases. Therefore, inches of mercury is the appropriate unit for measuring pressures below atmospheric pressure.

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• 43.

### Routine operation and maintenance of a hydronic heating system should include all the following except?

• A.

Confirming that automatic air vents are functional

• B.

Checking level of air cushion in expansion tank

• C.

Lubrication pump motors

• D.

Lubrication condensate pump

D. Lubrication condensate pump
Explanation
Routine operation and maintenance of a hydronic heating system should include confirming that automatic air vents are functional, checking the level of air cushion in the expansion tank, and lubricating pump motors. However, lubricating the condensate pump is not necessary as it does not require regular lubrication.

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• 44.

### A pump affects the pressure of a fluid or gas by?

• A.

Raising pressure

• B.

Reducing pressure

• C.

Regulating pressure

• D.

Stabilizing pressure

A. Raising pressure
Explanation
A pump affects the pressure of a fluid or gas by raising it. When a pump is activated, it creates a higher pressure in the system by increasing the energy of the fluid or gas. This is typically achieved by using mechanical force to push the fluid or gas into a confined space, which in turn increases the pressure. As a result, the pump is able to raise the pressure of the fluid or gas to the desired level for various applications such as pumping water to higher elevations or increasing the pressure in a hydraulic system.

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• 45.

### The steam boiler component used to lower the concentration of dissolved impurities in the boiler water is?

• A.

Blow-off connection

• B.

Deconcentrator

• C.

Feed connection

• D.

Sediment reduction valve

A. Blow-off connection
Explanation
A blow-off connection is a steam boiler component that is used to lower the concentration of dissolved impurities in the boiler water. It allows for the removal of accumulated sediment and dissolved solids from the boiler, helping to maintain the water quality and prevent damage to the boiler system. By opening the blow-off connection, the impurities are discharged from the boiler, ensuring that the water remains clean and free from excessive contaminants.

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• 46.

### To reduce corrosion in large hydronic heating systems, a gas cushion is recommended in the expansion tank consisting of?

• A.

Oxygen

• B.

Hydrogen

• C.

Nitrogen

• D.

Soluble gas

C. Nitrogen
Explanation
Nitrogen is recommended as a gas cushion in the expansion tank of large hydronic heating systems to reduce corrosion. Nitrogen is an inert gas that does not react with other substances, making it ideal for preventing oxidation and corrosion. By filling the expansion tank with nitrogen, it creates a protective barrier that helps to minimize the contact between the water and metal surfaces, reducing the chances of corrosion occurring.

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• 47.

### What is the maximum allowable working pressure of a boiler during hydrostatic testing?

• A.

100%

• B.

125%

• C.

150%

• D.

200%

C. 150%
Explanation
During hydrostatic testing, the maximum allowable working pressure of a boiler is typically set at 150% of its normal operating pressure. This is done to ensure that the boiler can withstand higher pressures without any risk of failure or leakage. By testing the boiler at a higher pressure, any potential weaknesses or defects can be identified and rectified before the boiler is put into regular operation. Therefore, 150% is the correct answer as it represents the maximum pressure that the boiler can safely handle during hydrostatic testing.

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• 48.

### If a 20-tooth pinion is turning at 120rpm and the driven gear has 60 teeth, the driven gear is turning at?

• A.

1 rpm

• B.

30rpm

• C.

40 rpm

• D.

360rpm

C. 40 rpm
Explanation
The driven gear has 3 times as many teeth as the pinion gear. Therefore, for every 1 revolution of the pinion gear, the driven gear will make 1/3 of a revolution. Since the pinion gear is turning at 120rpm, the driven gear will turn at 1/3 of that speed, which is 40rpm.

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• 49.

### The most common cause of feeder or low-water fuel cut-off trouble is the operator's failure to observe the?

• A.

Blow-down instructions

• B.

Fuel calibration sequence

• C.

Water treatment limitations

• D.

Low-water control calibration

A. Blow-down instructions
Explanation
The most common cause of feeder or low-water fuel cut-off trouble is the operator's failure to observe the blow-down instructions. Blow-down instructions refer to the process of removing sediment or impurities from the fuel system by draining a small amount of water or fuel. Failure to follow these instructions can lead to blockages or build-up of contaminants in the system, affecting its performance and causing trouble with the feeder or low-water fuel cut-off.

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• 50.

• A.

2 x π x R

• B.

π x R2 x 2

• C.

π x R2