# CDC 3E151B : Heating, Ventilation, And Refrigeration! Hardest Trivia Quiz

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Questions: 100 | Attempts: 770  Settings  Have you just finished the CDC 3E151B course on Heating, Ventilation, And Refrigeration? What is a better way there to see how attentive you are than showing off how much you learned? Take up this quiz and review what you learned. Be sure to post your score to see how you fair among others. All the best of luck!

• 1.

### Anything that has weight and takes up space is

• A.

Energy

• B.

Matter

• C.

Motion

• D.

Atoms

B. Matter
Explanation
Matter refers to anything that has weight and takes up space. It includes both living and non-living things, such as solids, liquids, and gases. Energy, on the other hand, refers to the ability to do work or cause a change. While energy can interact with matter, it is not considered matter itself. Motion and atoms are also not synonymous with matter, as motion refers to the change in position of an object, and atoms are the basic building blocks of matter. Therefore, the correct answer is matter.

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• 2.

### What is the relationship among matter, energy, and heat?

• A.

Energy is made up of atoms, which consists of electrons kept in motion by matter, which is a form of heat

• B.

Heat is made up of molecules, which consists of electrons kept in motion by energy, which is a form of matter

• C.

Matter is made of atoms, which consists of electrons kept by heat, which is a form of energy

• D.

Energy is made up of molecules, which consists of electrons kept in motion by heat, which is a form of matter

C. Matter is made of atoms, which consists of electrons kept by heat, which is a form of energy
Explanation
The correct answer states that matter is made of atoms, which consists of electrons kept by heat, which is a form of energy. This explanation accurately describes the relationship among matter, energy, and heat. Matter is composed of atoms, which have electrons that are kept in motion by heat. Heat is a form of energy, and it is the energy that causes the movement of electrons within atoms. Therefore, matter, energy, and heat are interconnected in this way.

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• 3.

### Conduction is the transfer of heat

• A.

Similar to that of light waves and radio waves

• B.

By the movement of a fluid such as air or water over a substance

• C.

Where a fan is used to propel the air across a hot or cold surface

• D.

Through a substance or from one body to another when the bodies are in direct contact

D. Through a substance or from one body to another when the bodies are in direct contact
Explanation
Conduction is the transfer of heat through a substance or from one body to another when the bodies are in direct contact. This means that heat energy is transferred from one object to another through direct physical contact, such as when you touch a hot pan and feel the heat being conducted from the pan to your hand. Conduction is different from the transfer of heat by light waves or radio waves, as it specifically involves the movement of a fluid, like air or water, over a substance or between two objects in direct contact.

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• 4.

### What form of heat transfer most commonly used in the HVAC indusrty is

• A.

Conduction

• B.

Convection

• C.

• D.

B. Convection
Explanation
Convection is the most commonly used form of heat transfer in the HVAC industry. Convection involves the transfer of heat through the movement of fluids, such as air or water. In HVAC systems, convection is used to distribute heated or cooled air throughout a space. This is typically achieved through the use of fans or blowers that circulate the air, allowing for efficient heating or cooling of a room or building. Convection is an important process in maintaining comfortable indoor temperatures and is widely utilized in HVAC systems.

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• 5.

### Sensible heat added to a substance will be indicated by a

• A.

Drop in temperature of that substance

• B.

Change in physical state of the substance

• C.

Stable temperature of that substance

• D.

Rise in temperature of that substance

D. Rise in temperature of that substance
Explanation
When sensible heat is added to a substance, it causes the temperature of the substance to increase. This is because sensible heat refers to the heat transfer that results in a change in temperature without a change in the physical state of the substance. Therefore, the correct answer is "rise in temperature of that substance."

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• 6.

### The heat that changes water at 212* F to steam at 212*F is known as

• A.

Latent heat of vaporization

• B.

Latent heat of condensation

• C.

Sensible heat of vaporization

• D.

Sensible heat of condensation

A. Latent heat of vaporization
Explanation
The heat that changes water at 212* F to steam at 212* F is known as latent heat of vaporization. This is because at this temperature, the water undergoes a phase change from liquid to gas without a change in temperature. The heat energy absorbed during this process is used to break the intermolecular forces between water molecules and convert them into vapor. This latent heat of vaporization is released when the vapor condenses back into liquid form.

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• 7.

### Which is the correct formula for converting Fahrenheit to Celsius?

• A.

F = (C x 1.8) + 32

• B.

F = (C x 1.8) - 32

• C.

C = (F - 32) / 1.8

• D.

C = (F + 32) / 1.8

C. C = (F - 32) / 1.8
Explanation
The correct formula for converting Fahrenheit to Celsius is C = (F - 32) / 1.8. This formula subtracts 32 from the Fahrenheit temperature and then divides the result by 1.8 to get the equivalent Celsius temperature.

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• 8.

### What is the specific volume of one pound of dry air at standard conditions?

• A.

13.33 cubic feet

• B.

0.016 cubic feet

• C.

29.92 inches mercury

• D.

62.4 pounds/cubic foot

A. 13.33 cubic feet
Explanation
The specific volume of a substance is defined as the volume occupied by a unit mass of that substance. In this question, we are asked to find the specific volume of one pound of dry air at standard conditions. The correct answer is 13.33 cubic feet, which means that one pound of dry air occupies a volume of 13.33 cubic feet. This value is derived from the properties of air and the given conditions.

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• 9.

### To the closest tenth, what is normal atmospheric presure sea level?

• A.

11 psi

• B.

14.7 psi

• C.

110 psi

• D.

340 psi

B. 14.7 psi
Explanation
Normal atmospheric pressure at sea level is approximately 14.7 psi. This is the average pressure exerted by the Earth's atmosphere on a given area at sea level. It is commonly used as a reference point for pressure measurements and is equivalent to 1 atmosphere or 101.325 kilopascals (kPa).

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• 10.

### Where would you likely find the fasest moving air within a duct?

• A.

Along the walls

• B.

At the top

• C.

At the bottom

• D.

In the center

D. In the center
Explanation
In a duct, the fastest moving air is likely to be found in the center. This is because air tends to follow the path of least resistance, and the center of the duct provides the least resistance to airflow. As the air moves towards the walls or the top and bottom of the duct, it encounters more friction and resistance, causing it to slow down. Therefore, the air in the center of the duct will be moving the fastest.

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• 11.

### Saturated steam is steam

• A.

• B.

At a temperature below boiling water

• C.

At a temperature above boiling water

• D.

At the temperature of boiling water

D. At the temperature of boiling water
Explanation
Saturated steam is steam that is at the temperature of boiling water. When water is heated to its boiling point, it starts to vaporize and form steam. Saturated steam is the point at which the water has absorbed enough heat to reach its boiling point and has completely vaporized. Therefore, it is at the same temperature as boiling water.

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• 12.

### To begin a plotting procedure on the psychometric chart, you must know the

• A.

Grains of moisture and specific heat

• B.

Dewpoint and wet-bulb temperatures

• C.

Wet-bulb and dry-bulb temperatures

• D.

Dry-bulb and dewpoint temperatures

C. Wet-bulb and dry-bulb temperatures
Explanation
To begin a plotting procedure on the psychometric chart, you must know the wet-bulb and dry-bulb temperatures. These two temperatures are essential in determining the properties of air and its moisture content. The wet-bulb temperature indicates the lowest temperature that can be achieved by evaporating water into the air, while the dry-bulb temperature represents the actual air temperature. By knowing these temperatures, one can accurately plot points on the psychometric chart to analyze and understand the thermodynamic properties of the air.

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• 13.

### Heat content i plotted on the psychometric chart by extending the

• A.

Relative humidity line

• B.

Dew point line

• C.

Dry-bulb line

• D.

Wet-bulb line

D. Wet-bulb line
Explanation
The wet-bulb line is plotted on the psychometric chart to represent the heat content. The wet-bulb temperature is the temperature that a parcel of air would have if it were cooled to saturation by the evaporation of water into it, with the latent heat being supplied by the parcel itself. This line helps in determining the amount of heat energy present in the air at different conditions.

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• 14.

### Refer to figure 1-10. If the wet-bulb temperature is 57*F and the dry-bulb temperature is 65*F, what is the relative humidity?

• A.

57 percent

• B.

61 percent

• C.

65 percent

• D.

70 percent

B. 61 percent
Explanation
Based on the given wet-bulb temperature of 57°F and dry-bulb temperature of 65°F, we can use a psychrometric chart to determine the relative humidity. By locating the intersection point of the wet-bulb and dry-bulb temperatures on the chart, we find that the corresponding relative humidity is approximately 61 percent.

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• 15.

### Which process follows the line of constant enthalpy or has no heat change?

• A.

Latent heat process

• B.

Sensible heat process

• C.

Moisture injection process

• D.

Explanation
The adiabatic saturation process follows the line of constant enthalpy or has no heat change. In this process, water vapor is added to the air without any heat transfer occurring. This results in an increase in the moisture content of the air without changing its enthalpy or temperature. Therefore, the adiabatic saturation process is the correct answer.

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• 16.

### The term for temperature control that uses no external source of energy is

• A.

Pneumatic

• B.

Electronic

• C.

Self-contained

• D.

Electromechanical

C. Self-contained
Explanation
Self-contained refers to a system or device that is able to operate independently without the need for any external source of energy. In the context of temperature control, a self-contained system would be able to regulate and maintain temperature without relying on any external energy source such as electricity or pneumatic power. Therefore, self-contained is the correct term for temperature control that uses no external source of energy.

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• 17.

### Hot-water reset is an example of what type of contol loop?

• A.

Open

• B.

Closed

• C.

Combination

• D.

Reverse reset

C. Combination
Explanation
Hot-water reset is an example of a combination control loop. This type of control loop combines both open and closed loop control strategies. In hot-water reset, the control loop adjusts the supply water temperature based on the outside temperature. It starts with an open loop strategy by using a schedule or setpoint to determine the supply water temperature. Then, it switches to a closed loop strategy by continuously monitoring the system and adjusting the supply water temperature based on the feedback from the outside temperature sensor. This combination of open and closed loop control allows for more efficient and precise control of the hot-water system.

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• 18.

### What is a typical application of floating control?

• A.

Static pressure in a variable air volume system

• B.

Controlling temperature in a laboratory

• C.

Hot water reset from outdoor air

• D.

Room and discharge

A. Static pressure in a variable air volume system
Explanation
A typical application of floating control is to regulate the static pressure in a variable air volume system. This control method allows for the adjustment of the static pressure based on the demand of the system, ensuring that the airflow remains constant even if the demand changes. By maintaining the desired static pressure, the system can effectively deliver the required amount of air to different zones or areas within a building.

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• 19.

### What mode of control corrects the problem of offset?

• A.

Proportional-plus-integral

• B.

Proportional-with-reset

• C.

Proportional

• D.

Floating

A. Proportional-plus-integral
Explanation
Proportional-plus-integral control is the mode of control that corrects the problem of offset. This control strategy combines both proportional and integral control actions to eliminate the offset. Proportional control provides a response proportional to the error, while integral control integrates the error over time to gradually reduce the offset. By using both actions together, proportional-plus-integral control ensures a more accurate and stable control system by continuously adjusting the control signal based on the error and its accumulated history.

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• 20.

### Use the following information to answer this question about a pneumatic sensor: What is the output pressure of a pneumatic sensor with a range of 0* to 100* F if the temperature measured is 24*F?

• A.

3.52 psi

• B.

5.88 psi

• C.

9.20 psi

• D.

11.60 psi

B. 5.88 psi
Explanation
The output pressure of a pneumatic sensor is directly proportional to the temperature measured. Since the temperature measured is 24°F, which is 24% of the total range (100°F), the output pressure would be 24% of the maximum output pressure. Therefore, the output pressure would be 24% of 24 psi, which is approximately 5.88 psi.

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• 21.

### Use the following information to answer this question about a pneumatic sensor: What is the output pressure of a pneumatic sensor with a range of  50* to 100* F if the temperature measured is 80*F?

• A.

3.0 psi

• B.

8.6 psi

• C.

9.4 psi

• D.

10.2 psi

D. 10.2 psi
Explanation
The output pressure of a pneumatic sensor is directly proportional to the temperature measured. Since the temperature measured is 80°F, which is 30°F below the maximum range of 100°F, the output pressure will be 30/50 (or 3/5) of the maximum output pressure. Therefore, the output pressure will be (3/5) * 17 psi (the difference between the minimum and maximum output pressure, which is 20 psi). Simplifying this calculation gives us an output pressure of 10.2 psi.

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• 22.

### Use the following information to answer this question about a single-input pneumatic controller: What is the proportional band required to obtain the desired performance?

• A.

5 percent

• B.

10 percent

• C.

15 percent

• D.

20 percent

B. 10 percent
Explanation
The proportional band required to obtain the desired performance is 10 percent. In a single-input pneumatic controller, the proportional band refers to the range around the setpoint where the controller's output will change in response to a deviation from the setpoint. A narrower proportional band (e.g., 5 percent) means that the controller will respond more quickly to deviations, but it may also cause more frequent and smaller adjustments. On the other hand, a wider proportional band (e.g., 20 percent) means that the controller will respond more slowly but with larger adjustments. Therefore, a proportional band of 10 percent strikes a balance between responsiveness and stability.

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• 23.

### Use the following information to answer this question about a single-input pneumatic controller: What is the ouput of the contoller at 70*F?

• A.

3 psi

• B.

8 psi

• C.

10 psi

• D.

13 psi

B. 8 psi
Explanation
Based on the information given, the output of the controller at 70°F is 8 psi.

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• 24.

### After you have drawn the performance graph for calibrating a single-input controller, what must you do next?

• A.

Find the transmitting pressure for both corners and the set point

• B.

Use a simulator in place of both sensors

• C.

Set the proportional

• D.

A. Find the transmitting pressure for both corners and the set point
Explanation
After drawing the performance graph for calibrating a single-input controller, the next step is to find the transmitting pressure for both corners and the set point. This is necessary to accurately adjust the controller and ensure optimal performance. The transmitting pressure values will help in determining the appropriate settings for the controller, allowing it to effectively regulate the system based on the desired set point.

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• 25.

### What is the last step in the calibration of a single-input pneumatic controller?

• A.

Adjust the calibration screw to equal the predicted output pressure

• B.

Adjust the sensors to the predicted output pressures

• C.

Disconnect the sensor simulators

• D.

A. Adjust the calibration screw to equal the predicted output pressure
Explanation
The last step in the calibration of a single-input pneumatic controller is to adjust the calibration screw to equal the predicted output pressure. This is necessary to ensure that the controller is accurately responding to the input and producing the desired output pressure. By adjusting the calibration screw, the controller can be fine-tuned to match the predicted output pressure, allowing for precise control and accuracy in the system.

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• 26.

### What is the main difference in calibration between a single-input controller with remote sensor and one with a built-in sensor?

• A.

The dials must all be set to the specified values

• B.

The temperature must be measured at the sensor

• C.

A temperature simulator cannot be used in calibration

• D.

You must allow extra time for the system to stabilize

C. A temperature simulator cannot be used in calibration
Explanation
The main difference in calibration between a single-input controller with a remote sensor and one with a built-in sensor is that a temperature simulator cannot be used in calibration. This means that when calibrating a single-input controller with a remote sensor, a temperature simulator cannot be used to simulate different temperature conditions for calibration purposes. On the other hand, when calibrating a single-input controller with a built-in sensor, a temperature simulator can be used to simulate different temperature conditions for calibration.

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• 27.

### If you are calibrating a contoller with a built-in sensor and you have adjusted the controller calibration screw to equal Pcal, your next step is to adjust the

• A.

Set point dial up by one-half the TRc

• B.

Sensitivity slides

• C.

Calibration screw

• D.

Pressure span

A. Set point dial up by one-half the TRc
Explanation
After adjusting the controller calibration screw to equal Pcal, the next step is to adjust the set point dial up by one-half the TRc. This means increasing the set point by half of the TRc value. This adjustment is necessary to ensure that the controller is properly calibrated and will respond accurately to changes in the system. By adjusting the set point dial, the controller will be able to maintain the desired temperature, pressure, or any other variable being controlled.

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• 28.

### On a pneumatic dual-input receiver controller, one sensor measures the primary variable. What does the second sensor measure?

• A.

Desired variable

• B.

Reset variable

• C.

Set point

• D.

Offset

B. Reset variable
Explanation
The second sensor on a pneumatic dual-input receiver controller measures the reset variable. This variable is used to adjust the controller's output in order to bring the primary variable back to the desired value. The reset variable helps maintain stability and accuracy in the control system by continuously adjusting the controller's output based on the deviation from the desired value.

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• 29.

### When the primary variable set point of a pneumatic dual-input controller decreases as the reset variable increases, what is the reset?

• A.

Counter

• B.

Straight

• C.

Direct

• D.

Reverse

D. Reverse
Explanation
In a pneumatic dual-input controller, the reset variable refers to a parameter that determines how quickly the controller responds to deviations from the set point. When the primary variable set point decreases as the reset variable increases, it indicates a reverse relationship between the two variables. This means that as the reset variable increases, the controller's response becomes slower, causing the primary variable set point to decrease. Therefore, the correct answer is "reverse."

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• 30.

### When calibrating a dual-input pneumatic controller, you adjust sensors oneand two to the set point value. Your next step is to adjust the

• A.

Action

• B.

Proportional band

• C.

Percent authority

• D.

Output pressure to equal calibration pressure (Pcal)

D. Output pressure to equal calibration pressure (Pcal)
Explanation
After adjusting the sensors one and two to the set point value, the next step in calibrating a dual-input pneumatic controller is to adjust the output pressure to equal the calibration pressure (Pcal). This ensures that the controller is accurately responding to the input signals and producing the desired output. By adjusting the output pressure to match the calibration pressure, the controller can be fine-tuned to operate within the desired range and provide accurate control over the system.

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• 31.

### After you have adjusted the proportinal band and percent authority on a dual-input controller, your next step is to

• A.

Draw performance graph

• B.

Find the sensor pressures

• C.

Disconnect both sensors and connect the simulator

• D.

Measure the output pressure

A. Draw performance graph
Explanation
After adjusting the proportional band and percent authority on a dual-input controller, the next step is to draw a performance graph. This graph helps visualize the controller's response and performance in relation to the setpoint. By plotting the output pressure against time, any deviations or oscillations can be identified, allowing for further adjustments or troubleshooting if necessary. It is a crucial step in assessing the controller's effectiveness and ensuring optimal system performance.

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• 32.

### When the pressure to the control point adjustment port of a pneumatic controller increases,the setpoint

• A.

Stabilizes

• B.

Decreases

• C.

Increases

• D.

Stays the same

C. Increases
Explanation
When the pressure to the control point adjustment port of a pneumatic controller increases, the setpoint increases. This is because the increase in pressure causes the controller to respond by increasing the desired setpoint value. This adjustment ensures that the controller maintains the desired level of control and compensates for any changes or disturbances in the system.

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• 33.

### What is the easiest way to calibrate a pneumatic controller with a control point adjustment port?

• A.

Allow the system time to stabilize; then calibrate

• B.

Disconnect the control point adjustment pressure and calibrate the controller

• C.

Adjust the control point adjustment to maximum pressure; then, use the dual-input calibration procedures

• D.

Return the control point adjustment port to the calibration pressure; then, use the single-input calibration procedures

D. Return the control point adjustment port to the calibration pressure; then, use the single-input calibration procedures
Explanation
The easiest way to calibrate a pneumatic controller with a control point adjustment port is to return the control point adjustment port to the calibration pressure and then use the single-input calibration procedures. This means that after adjusting the control point adjustment to the desired pressure, the controller can be calibrated using the single-input calibration procedures. This method ensures that the controller is accurately calibrated and ready for use.

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• 34.

### Use the following information to answer the question: Honeywell 908B Total change set point = 10*F Total change CPA pressure = 5 psi Span of sensor = 100*F (0* to 100*F) If you used the second port of a pneumatic dual-input controller as a control adjustment, what should the authority setting be to obtain the desired performance?

• A.

6 percent

• B.

12 percent

• C.

24 percent

• D.

48 persent

C. 24 percent
Explanation
The authority setting determines the percentage of the controller's output that is used to adjust the control valve. In this case, the desired performance is not specified, so it is unclear what specific outcome is being aimed for. However, based on the given information, the total change in set point is 10*F and the span of the sensor is 100*F. The authority setting needs to be set at a value that allows for a total change in set point of 10*F. Since the span of the sensor is 100*F, an authority setting of 24 percent (24% of 100*F = 24*F) would allow for a total change in set point of 10*F. Therefore, the correct answer is 24 percent.

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• 35.

### How does a mimimum-poisition pneumatic adapter relay work?

• A.

It will not allow output pressure to fall below a preset value

• B.

It selects both the high and low signal

• C.

It changes the signal from direct-acting to reverse-acting

• D.

It will not allow the output pressure to go above a preset value

A. It will not allow output pressure to fall below a preset value
Explanation
The correct answer is that a minimum-position pneumatic adapter relay will not allow the output pressure to fall below a preset value. This means that the relay is designed to maintain a minimum pressure level in the system and prevent it from dropping below that value. This can be important in certain applications where maintaining a minimum pressure is necessary for proper operation or safety reasons.

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• 36.

### What is one type of controlled device used in pneumatice system?

• A.

Actuator

• B.

Switching relay

• C.

Square root extractor

• D.

Minimum position switch

A. Actuator
Explanation
An actuator is a type of controlled device used in pneumatic systems. It is responsible for converting energy into mechanical motion. Actuators are commonly used to control valves, dampers, and other mechanical components in pneumatic systems. They play a crucial role in regulating the flow of compressed air and controlling the movement of various parts in the system. Therefore, an actuator is the correct answer in this context.

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• 37.

### What function does spring range have in a pneumatic system?

• A.

The pressure range over which a high/low selector operates

• B.

The pressure range over which a program switch operates

• C.

The pressure range over which a actuator operates

• D.

The pressure range of a controller's internal parameters

C. The pressure range over which a actuator operates
Explanation
The spring range in a pneumatic system refers to the pressure range over which an actuator operates. The actuator is a component that converts pneumatic energy into mechanical motion, and the spring range determines the range of pressures within which the actuator can function effectively. This range is important for ensuring that the actuator can perform its intended tasks within the specified pressure limits.

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• 38.

### Where isthe best place to mount the components of a pneumatic control system?

• A.

Close to the equipment it is controlling

• B.

On a steady base away from vibration

• C.

On the side of an air handler

• D.

Close to main air supply

B. On a steady base away from vibration
Explanation
The best place to mount the components of a pneumatic control system is on a steady base away from vibration. This is because vibrations can interfere with the proper functioning of the system and cause inaccuracies in the control. Mounting the components on a steady base ensures stability and reduces the risk of vibrations affecting the system's performance.

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• 39.

### When you troubleshoot a pneumatic control system, the first component you check is the

• A.

Sensor

• B.

Controller

• C.

• D.

Controlled device

D. Controlled device
Explanation
When troubleshooting a pneumatic control system, the first component to check is the controlled device. This is because the controlled device is the final component in the system that receives the signals and performs the desired action. By checking the controlled device first, you can determine if it is functioning properly and if any issues with the system are related to its operation. Once the controlled device is confirmed to be working correctly, you can then proceed to check the other components in the system, such as the sensor, controller, and adapter, if necessary.

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• 40.

### What is the first step in cleaning up a contaminated pneumatic air supply?

• A.

Calibrate the instruments

• B.

Use a degreasing compound

• C.

Stop the contamination at the source

• D.

Retrofit the compressor air supply equipment

C. Stop the contamination at the source
Explanation
The first step in cleaning up a contaminated pneumatic air supply is to stop the contamination at the source. This means identifying and addressing the cause of the contamination, such as a leak or malfunctioning equipment, and taking measures to prevent further contamination. Calibrating the instruments, using a degreasing compound, or retrofitting the compressor air supply equipment may be necessary steps in the overall cleaning process, but they should come after stopping the contamination at the source.

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• 41.

### What should you do after you remove the vapor degreasing compound from a pneumatic system?

• A.

Turn on the fans

• B.

Calibrate the controller

• C.

Change the filters in the controller

• D.

Flush the system with a clean air supply

D. Flush the system with a clean air supply
Explanation
After removing the vapor degreasing compound from a pneumatic system, the next step should be to flush the system with a clean air supply. This is necessary to remove any remaining residue or contaminants from the system, ensuring its proper functioning. Flushing the system with clean air helps to maintain the system's efficiency and prevent any potential damage or malfunctions.

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• 42.

### The two main types of switches used in electronic controls are

• A.

Double pole, double throw and double pole, single throw

• B.

Single pole, double throw and single pole, single throw

• C.

Snap acting and mercury switch

• D.

Thermostatic and mercury

C. Snap acting and mercury switch
Explanation
The correct answer is snap acting and mercury switch. Snap acting switches are commonly used in electronic controls as they provide a quick and reliable response. They have a spring mechanism that allows them to rapidly switch between two positions. On the other hand, mercury switches use a small amount of mercury inside a glass tube to create a conductive path when tilted or moved. They are often used in applications where precise and stable switching is required.

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• 43.

### What is the advantage of timed, two-position control?

• A.

The final control elements moves to a position equal to the amount the controlled variable moved

• B.

The controller never catches up with the controlled condition

• C.

It greatly reduces the swings in the controlled variable

• D.

The thermal timer will cool

C. It greatly reduces the swings in the controlled variable
Explanation
Timed, two-position control greatly reduces the swings in the controlled variable. This means that the final control element (such as a valve or damper) moves to a position equal to the amount the controlled variable moved, but it does so in a timed manner. This prevents the controller from constantly trying to catch up with the controlled condition, which can lead to overshooting and instability. By reducing swings in the controlled variable, timed, two-position control helps maintain a more stable and consistent process or system.

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• 44.

### A major problem of proprotional control is

• A.

Offset

• B.

Sensitivity

• C.

The throttling range

• D.

The position of the final element

A. Offset
Explanation
Offset is a major problem of proportional control. Offset refers to the difference between the desired setpoint and the actual process variable. In proportional control, the controller output is directly proportional to the error between the setpoint and the process variable. However, due to factors such as system dynamics and disturbances, the process variable may not reach the setpoint exactly, resulting in a steady-state error or offset. This can lead to instability and reduced control performance in the system.

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• 45.

### When special requirements are line voltage, two-position, and "fail-safe," the type of electrical control motor you should use to operate a damper isthe series

• A.

40

• B.

60

• C.

80

• D.

90

A. 40
Explanation
When special requirements include line voltage, two-position, and "fail-safe," the appropriate type of electrical control motor to use for operating a damper is the series 40.

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• 46.

### The difference between a series 60 and a series 40 two-position motor is that the series 40 is

• A.

A line voltage circuit

• B.

A fail-safe control circuit

• C.

Used mainly where hazardous conditions exist

• D.

Unusable when single-pole,double throw control of line voltage is required

B. A fail-safe control circuit
Explanation
The series 40 motor is described as a fail-safe control circuit. This means that it is designed to automatically shut down or switch to a safe state in the event of a failure or fault. This feature ensures that the motor will not continue to operate in a potentially dangerous or hazardous condition. In contrast, the other options do not describe the series 40 motor accurately.

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• 47.

### When the temperature increases above the set point in series 90 controller controlling a face andbypass damper cooling system, the motor will

• A.

Operate clockwise

• B.

Close the face dampers

• C.

Open the face dampers

• D.

Open the chilled water

C. Open the face dampers
Explanation
When the temperature increases above the set point in a series 90 controller controlling a face and bypass damper cooling system, the motor will open the face dampers. This is because when the temperature rises, the system needs to cool down the space. Opening the face dampers allows more cool air to enter the space, helping to lower the temperature.

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• 48.

### The rear pot in the series controller controls the

• A.

Face and bypass dampers

• B.

Reheat value

• C.

Temperature

• D.

Steam coil

B. Reheat value
Explanation
The rear pot in the series controller controls the reheat value. This means that it regulates the amount of heat added to the air after it has been cooled by the cooling coil. By adjusting the reheat value, the controller can control the temperature of the air leaving the system.

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• 49.

### What meter should you use to check a two-posistion control without power?

• A.

Ammeter

• B.

Voltmeter

• C.

Ohmmeter

• D.

Anemometer

C. Ohmmeter
Explanation
An ohmmeter is used to measure the resistance in a circuit. In this case, since the two-position control is without power, the ohmmeter can be used to check if there is continuity or a break in the circuit. By connecting the ohmmeter to the two terminals of the control, it can determine if there is a complete path for the current to flow or if there is a break in the circuit. This can help identify any faults or issues with the control even without power.

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• 50.

### What sould you do after installing a new eletrical control?

• A.

Give it a complete operational checkout

• B.

The resistance should be dropped

• C.

Handle control carefully

• D.

Replace the cover Back to top