4B Air Distribution Fans and Ducts Coils

Question 1

The propeller axial flow fan:

a. Is the least economical fan used to produce high capacity low, pressure air movement.
b. Finds application in unit heaters, air-cooled condensers, and as an exhaust fan for ventilation purposes.
c. Is used in commercial air conditioning ducting.
d. Requires the least power at minimum air delivery.
e. Is used in ducted air distribution systems.

Answer 1

b. Finds application in unit heaters, air-cooled condensers, and as an exhaust fan for ventilation purposes

Question 2

Which of the following statements about fan performance curves is false:

a. They are plotted from theoretical calculations.
b. The curve is a plot of static pressure against air volume delivery.
c. The curve is a plot of horse, power against air volume delivery
d. The curve is a plot of static efficiency against air volume delivery.
e. The curve range is from shutoff to free delivery.

Answer 2

a. They are plotted from theoretical calculations.

Question 3

Axial flow fans:

a. Have maximum horsepower requirements at maximum or free air delivery.
b. Have minimum horsepower at maximum or free air delivery.
c. Are not the logical choice to move large volumes of air at low, pressures.
d. Are the least economical fans used to produce high capacity low, pressure air movement.
e. Are quieter than centrifugal fans

Answer 3

b. Have minimum horsepower at maximum or free air delivery.

Question 4

The fan which discharges maximum air delivery at the lowest power requirement and is used mainly to produce large air movements at low pressures is the:

a. Propeller fan.
b. Tube axial fan.
c. Backward inclined blade fan.
d. Radial blade fan.
e. Forward curved blade fan.

Answer 4

a. Propeller fan.

Question 5

When comparing the tube axial fan with the vane axial fan the main difference between the two is the:

a. Noise output.
b. Location of the fans in the system.
c. Location of the fan bearings.
d. Size of the two units.
e. Motion of the discharge air.

Answer 5

e. Motion of the discharge air.

Question 6

Control of the static pressure and horsepower requirements at a given speed is obtained by using:

a. Direct drives.
b. Fluid drives.
c. Outlet damper control.
d. Variable inlet vane control.
e. Belt Guards.

Answer 6

d. Variable inlet vane control.

Question 7

Two fan wheels are rotating at the same speed. One wheel has forward curved blades and the other has backward inclined blades. The velocity of the air leaving the forward curved blades is considerably higher for which of the following reasons?

a. The centrifugal force of the forward curved blades is higher.
b. The forward motion of the forward curved blades is higher.
c. The air resistance of the backward inclined blades is much lower.
d. The inclination of the blades in the forward curved fan increases the resultant force vector while the backward inclined blade inclination decreases the resultant vector.
e. All of the above.

Answer 7

d. The inclination of the blades in the forward curved fan increases the resultant force vector while the backward inclined blade inclination decreases the resultant vector.

Question 8

Which of the following is not a centrifugal fan?

a. Backward inclined fan wheel.
b. Forward curved fan wheel.
c. The propeller fan.
d. Radial blade fan.
e. Backward inclined airfoil blade fan.

Answer 8

c. The propeller fan.

Question 9

Backward inclined centrifugal fans:

a. Require more horsepower than the forward curved fans to deliver a specified volume of air.
b. Are quieter than forward curved fans.
c. Are less efficient than forward curved fans.
d. Operate at lower speeds than forward curved fans.
e. Are noisier than forward curved fans.

Answer 9

b. Are quieter than forward curved fans.

Question 10

Which of the following devices has a de-clutching feature?

a. A fluid drive.
b. An outlet damper control.
c. A variable inlet vane control.
d. A variable speed motor control.
e. A V-belt drive.

Answer 10

a. A fluid drive.

Question 11

The two general groups of fans are:

a. Rotary positive displacement and centrifugal.
b. Reciprocating and centrifugal.
c. Reciprocating and axial flow.
d. Positive displacement and axial flow.
e. Centrifugal and axial flow.

Answer 11

e. Centrifugal and axial flow.

Question 12

The devices that are used to minimise vibration problems and premature wearing of the belts are called:

a. Direct drives.
b. Balanced Sheaves.
c. V-Belt drives.
d. Fluid drives.
e. Outlet damper controls

Answer 12

b. Balanced Sheaves.

Question 13

Axial flow fans are classified as:

a. Centrifugal and propeller.
b. Vane axial and centrifugal.
c. Tube axial and rotary positive displacement.
d. Vane axial, tube axial, and propeller.
e. Centrifugal and turbine

Answer 13

d. Vane axial, tube axial, and propeller

Question 14

Backward inclined airfoil fans:

a. Are mostly used for low capacity high, pressure applications.
b. Are mostly used for high capacity low, pressure applications.
c. Are mostly used for high capacity high, pressure applications.
d. Have a lower initial cost than the plain backward inclined fan.
e. Are less efficient than the plain backward inclined fan.

Answer 14

c. Are mostly used for high capacity high, pressure applications.

Question 15

The vane axial flow fan:

a. Has a more spiral air, flow than the tube axial fan.
b. Has more turbulent air, flow than the tube axial fan.
c. Has lower efficiency than the tube axial fan.
d. Has less spiral air, flow, less friction, and better efficiency than the tube axial fan.
e. Is not suitable for duct mounting

Answer 15

Has less spiral air, flow, less friction, and better efficiency than the tube axial fan

Question 16

When a fan outlet is considered fully open which of the following statements is true?

a. Vane axial fans have maximum horsepower requirements.
b. The pressure volume curve of a backward inclined fan increases.
c. There is free air volume delivery.
d. The power requirements for a forward curved fan are at a minimum.
e. Air volume delivery is considered a minimum.

Answer 16

c. There is free air volume delivery.

Question 17

Static pressure exerted by air is measured by connecting a:

a. Manometer at right angles to the air duct.
b. Bourdon tube pressure gage to the air duct.
c. Pressure gage with the opening with the opening facing air, flow.
d. Manometer with the opening facing the air, flow.
e. Manometer to the fan.

Answer 17

a. Manometer at right angles to the air duct.

Question 18

Forward curved centrifugal fans:

a. Operate at a lower speed than backward inclined fans for the same air volume.
b. Operate at a higher speed than backward inclined fans for the same air volume.
c. Require less horsepower than backward inclined fans to deliver a specified air volume.
d. Are more efficient than backward inclined fans.
e. Are quieter than backward inclined fans.

Answer 18

a. Operate at a lower speed than backward inclined fans for the same air volume.

Question 19

Forward curved fans:

a. Require larger size shafts than backward inclined fans.
b. Are desirable when air, handling units have two or more fans mounted on a common shaft.
c. Operate at higher speeds than backward inclined fans.
d. Are quieter than backward inclined fans.
e. Are more desirable for large fans

Answer 19

b. Are desirable when air, handling units have two or more fans mounted on a common shaft.

Question 20

The tube axial flow fan:

a. Has higher friction losses in ducts than the straight air, flow of a centrifugal fan.
b. Has lower friction losses in ducts than the centrifugal fan.
c. Is quiet in operation.
d. Produces lower pressure than the propeller fan.
e. Is not suitable for duct mounting.

Answer 20

a. Has higher friction losses in ducts than the straight air, flow of a centrifugal fan

Question 21

Total pressure exerted by the air is the sum of:

a. Head pressure, suction pressure, and velocity pressure.
b. Head pressure and suction pressure.
c. Head pressure and velocity pressure.
d. Static pressure and velocity pressure.
e. Suction pressure and velocity pressure.

Answer 21

d. Static pressure and velocity pressure.

Question 22

The propeller axial flow fan is used:

a. For low capacity, high pressure applications.
b. For low capacity, low pressure applications.
c. For high capacity, high pressure applications.
d. For high capacity, low pressure applications.
e. In ducted air distribution systems

Answer 22

d. For high capacity, low pressure applications.

Question 23

Velocity pressure exerted by the air is measured by connecting a:

a. Manometer at right angles to the air duct.
b. Manometer in the air duct with the inlet opening facing into the air, flow and the outlet opening at right angles to the air duct.
c. Manometer to the fan.
d. Bourdon tube pressure gage to the air duct.
e. Pressure gage at right angles to the air duct

Answer 23

b. Manometer in the air duct with the inlet opening facing into the air, flow and the outlet opening at right angles to the air duct.

Question 24

Centrifugal fans are classified as:

a. Backward inclined.
b. Straight.
c. Backward inclined with airfoil blades.
d. Forward curved.
e. All of the above.

Answer 24

e. All of the above

Question 25

The group of fans that consist of a rotor or wheel having several radial blades, which is mounted on a shaft within the fan housing are called:

a. Axial flow fans
b. Centrifugal fans
c. Both axial flow and centrifugal fans
d. Archial cage fans
e. None of the above.

Answer 25

b. Centrifugal fans

Question 26

What are the three different kinds of pressure developed by a fan?

a. Static pressure, head pressure, suction pressure.
b. Velocity pressure, head pressure, suction pressure.
c. Static pressure, velocity pressure, total pressure.
d. Head pressure, suction pressure, total pressure.
e. Static pressure, head pressure, total pressure

Answer 26

c. Static pressure, velocity pressure, total pressure

Question 27

A ventilation system leading from a fume hood in a chemistry lab would have which duct material used for its ductwork?

a. Galvanised steel sheet metal.
b. Aluminium sheet metal.
c. Cement asbestos.
d. Black steel sheet metal.
e. Fiberglas.

Answer 27

c. Cement asbestos

Question 28

When all supply air duct is outside the conditioned space there is a certain leakage. This leakage must be calculated how?

a. It must be added to the calculated room sensible heat load.
b. It must be added to the calculated room specific latent humidity load.
c. It must be subtracted from the return air duct leakage.
d. It must be added to the return air duct leakage.
e. It need not be considered in loss calculation

Answer 28

a. It must be added to the calculated room sensible heat load

Question 29

The main function of an air conditioning duct system is to:

a. Only transmit return air from the space to be conditioned.
b. Transmit air form the refrigeration compressor to the condenser.
c. Only transmit air to the refrigeration compressor.
d. Transmit supply and return air between the air handling apparatus and the space to be conditioned.
e. Only transmit supply air from the air handling apparatus

Answer 29

d. Transmit supply and return air between the air handling apparatus and the space to be conditioned

Question 30

Which of the following statements about duct leakage losses is true?

a. The effects of air leakage in supply air ducts are the same as those in return ducts.
b. Losses due to air leakage from furred supply air ducts within the conditioned space can only be evaluated on the basis of judgement.
c. Leakage inspection can only be done after the duct is covered in insulation.
d. Losses from bare supply air ducts within the conditioned space have a substantial impact on loss calculations.
e. Air leakage varies from 40% to 45%.

Answer 30

b. Losses due to air leakage from furred supply air ducts within the conditioned space can only be evaluated on the basis of judgement.

Question 31

Seepage in return air ducts returned within the conditioned space may have what kind of effect?

a. It will add to the amount of air needed to supply the cooled space.
b. It will ruin the duct’s insulation.
c. It will increase the load on the air system in terms of volumes of air.
d. It will increase the load on the air system in terms of pressure.
e. It will create a loss of cooling effect.

Answer 31

c. It will increase the load on the air system in terms of volumes of air.

Question 32

Modulating dampers in air handling systems are used:

a. As mixing boxes to proportion the amounts of two different air flows such as outdoor air and recirculated air.
b. To modulate the volume of conditioned air needed to meet load requirements.
c. As face dampers to modulate the volume of air that goes through a cooling or heating coil.
d. As bypass dampers to throttle the balance of the constant total air, flow around a heating or cooling coil.
e. All of the above.

Answer 32

e. All of the above.

Question 33

The function of a check valve is similar to the function of which type of damper?

a. A manual damper.
b. A modulating damper.
c. A two-position damper.
d. A relief damper.
e. A louver.

Answer 33

d. A relief damper

Question 34

A mixing box is an example of which kind of damper?

a. A manual damper.
b. A modulating damper.
c. A two -position damper.
d. A relief damper.
e. A louver.

Answer 34

b. A modulating damper

Question 35

Semi-rigid fibrous glass blankets attached to the insides of the ducts are in place to mainly serve which function?

a. To restrict spread of smoke.
b. To insulate.
c. To act as a fire retardant.
d. To attenuate airborne noises.
e. To stop leakage in the seams of the duct work.

Answer 35

d. To attenuate airborne noises.

Question 36

Which of the following is not a function of terminal air distribution devices?

a. Distribute the air to the spaces.
b. Provide uniform space temperatures.
c. Control or counteract the effects of conduction, convection and radiation.
d. Provide adequate air motion.
e. To create local still pockets of air.

Answer 36

e. To create local still pockets of air.

Question 37

Return air duct leakage calculations include:

a. 3% seepage if the return air duct is outside the conditioned space.
b. 3% seepage if the return air duct is both inside and outside the conditioned space.
c. 10% leakage if the return air duct is inside the conditioned space.
d. 3% leakage if the return air duct is inside the conditioned space.
e. 5% seepage if the return air duct is outside the conditioned space.

Answer 37

a. 3% seepage if the return air duct is outside the conditioned space

Question 38

Short radius elbows should be provided with what?

a. Stiffeners.
b. Turning vanes.
c. Mitre elbows.
d. Positive lock dampers.
e. Flexible connections

Answer 38

b. Turning vanes

Question 39

Ducts are fabricated of:

a. Sheet metal.
b. Cement asbestos.
c. Plastic.
d. Fibreglass.
e. All of the above

Answer 39

e. All of the above

Question 40

Parallel blade dampers:

a. Are used only in small sizes with low velocity air.
b. Are used when modulation of air flow is required.
c. Have blades linked so adjacent blades rotate in opposite directions.
d. Are often used on mixing boxes where two sets of dampers are mounted with the blades directing the air, flow.
e. Are not suited for two position damper operation.

Answer 40

d. Are often used on mixing boxes where two sets of dampers are mounted with the blades directing the air, flow.

Question 41

Functions of terminal air distribution devices are accomplished:

a. Only by diffusion.
b. Only by diffusion and aspiration.
c. By aspiration, entrainment, induction, and diffusion.
d. Only by entrainment and diffusion.
e. Only by entrainment and aspiration.

Answer 41

c. By aspiration, entrainment, induction, and diffusion.

Question 42

Ducts of large dimensions must be diagonally creased for what reason?

a. To provide stiffness.
b. To allow gradual duct size change.
c. To decrease duct weight.
d. To increase air velocity.
e. To decrease air friction in the duct work

Answer 42

a. To provide stiffness

Question 43

Materials used in sheet metal ducts are:

a. Only copper.
b. Only aluminium.
c. Only stainless steel.
d. Galvanised or black steel, aluminium, copper, and stainless steel.
e. Only galvanised or black steel

Answer 43

d. Galvanised or black steel, aluminium, copper, and stainless steel

Question 44

18. Relief dampers:
    a. Allow air, flow in both directions.
    b. Allow air, flow in one direction only.
    c. Allow air mixing.
    d. Are the same as bypass dampers.
    e. Are the same as face dampers

Answer 44

b. Allow air, flow in one direction only.

Question 45

Duct liners:

a. Eliminate corrosion.
b. Reduce the noise level of air flowing in the duct system.
c. Reduce fire hazard.
d. Increase erosion to the duct.
e. Increase the pressure.

Answer 45

b. Reduce the noise level of air flowing in the duct system

Question 46

The purpose of dampers in an air handling system is to:

a. Control the flow of air.
b. Regulate refrigeration compressor speed.
c. Control the flow of water in a hot water heating system.
d. Regulate the fire in heating boilers.
e. Control the flow of cooling water in a system.

Answer 46

a. Control the flow of air.

Question 47

Dampers in air handling systems may only be:

a. Manual and modulating.
b. Modulating.
c. Modulating, manual and two position.
d. Manual and two position.
e. Two position.

Answer 47

c. Modulating, manual and two position.

Question 48

Which of the following is not a function of terminal air distribution devices?

a. Control or counteract the effects of conduction, radiation, and convection.
b. Provide adequate air motion to prevent local still pockets of air without excess drafts.
c. Maintain comfortable conditions mainly along the ceiling and outside walls within the occupied zone.
d. Distribute the air to the spaces.
e. Provide uniform space temperatures

Answer 48

c. Maintain comfortable conditions mainly along the ceiling and outside walls within the occupied zone.

Question 49

Medium and high, pressure duct systems require less space than low, pressure duct systems, but this feature is partly offset by:

a. Higher operating cost and higher initial cost of air handling apparatus.
b. Costly special control devices and costly noise suppressing devices.
c. Higher first cost for special equipment is required to reduce the air velocity before distribution to the air space.
d. More costly fabrication and installation of ductwork.
e. All of the above.

Answer 49

e. All of the above.

Question 50

Air louvers are:

a. Often used for mixing boxes.
b. Always used for fire and smoke dampers.
c. Suited for two position damper operation.
d. Used in fresh air intake openings to minimise the amount of water and snow entering the air handling system.
e. Used as relief dampers

Answer 50

d. Used in fresh air intake openings to minimise the amount of water and snow entering the air handling system.

Question 51

Classifications of air conditioning ducts include:

a. Low pressure and medium pressure.
b. Low pressure, medium pressure, and high pressure.
c. Medium pressure and high pressure.
d. Absorption and compression.
e. Heating and cooling.

Answer 51

b. Low pressure, medium pressure, and high pressure

Question 52

Damper designs include:

a. Only parallel blade types.
b. Only single blade types.
c. Opposed blade, parallel blade, and single blade types.
d. Only opposed blade types.
e. None of the above.

Answer 52

c. Opposed blade, parallel blade, and single blade types.

Question 53

Fibreglass ducts are used:

a. In high pressure systems.
b. To handle air with high moisture levels or oil and grease.
c. Where its heavy weight is not a problem.
d. Where high strength is required.
e. In some low pressure systems.

Answer 53

e. In some low pressure systems.

Question 54

Supply air duct leakage loss calculations include:

a. 20% leakage loss when the supply air duct is outside the conditioned space.
b. Losses from bare supply air ducts within the conditioned space.
c. 10% leakage loss when the supply air duct is outside the conditioned space.
d. 5% leakage loss when the supply air duct is outside the conditioned space.
e. 10% leakage loss when some of the supply air duct is outside the conditioned space and some inside.

Answer 54

c. 10% leakage loss when the supply air duct is outside the conditioned space.

Question 55

To ensure effective heat transfer which of the following is the most vital element?

a. The fin must be crimped.
b. Highly conductive material used in fins.
c. A good bond must exist between the tube and fin.
d. High fin spacing.
e. Low fin spacing

Answer 55

c. A good bond must exist between the tube and fin.

Question 56

Steam Coils must be designed to:
1. Constantly eliminate air.
2. Constantly eliminate condensate.
3. Constantly eliminate non-condensable gases.
4. Constantly maintain face velocity.
5. Constantly eliminate air venting.
In order to provide uniform steam distribution to the individual tubes, which of the above design parameters is/are true?
a. 2, 3, 5
b. 3
c. 2, 4
d. 1, 3, 4, 5
e. 1, 2, 3.

Answer 56

e. 1, 2, 3.

Question 57

Face velocity is the:

a. Velocity of the supply water to the coil.
b. Velocity of the air before it enters the coil.
c. Velocity of the air after it leaves the coil.
d. Average velocity of the air flowing over the face area of the fin surface.
e. Velocity of the return water from the coil.

Answer 57

d. Average velocity of the air flowing over the face area of the fin surface.

Question 58

Which type of coil circuiting is designed to produce a high heat capacity with limited water quantity?

a. Single serpentine.
b. Double serpentine.
c. Half serpentine.
d. Face velocity.
e. Steam coil

Answer 58

c. Half serpentine.

Question 59

Which of the following statements about coil surfaces is false?

a. Finned coils are less expensive than smooth coils of the same capacity.
b. Finned coils are more compact than smooth tube coils of the same capacity.
c. Fins increase the contact surface area between the air stream and the tubes.
d. All fins must be crimped.
e. Air flows across the fins

Answer 59

d. All fins must be crimped.

Question 60

Which of the following is a limiting factor for the number of fins that can be used?

a. Temperature of steam in coils.
b. Temperature of chilled water in the coils.
c. Fin material.
d. Resistance to airflow.
e. Face velocity

Answer 60

d. Resistance to airflow.

Question 61

Which of the following statements about steam distributing coils is true?

a. The coils never freeze.
b. The coils distribute steam evenly over the entire coil.
c. The coils are used when steam cannot be throttled.
d. The coils cannot be used where freezing air temperatures are frequently encountered over the coil.
e. The coils can only have same end connections.

Answer 61

b. The coils distribute steam evenly over the entire coil.

Question 62

Which one of the following methods is not a method of ensuring uniform steam distribution in steam coils?

a. Installation of distributing plates within the steam header.
b. Controlling the face velocity of the air flowing over coils.
c. Installation of individual orifices into the supply end of each tube.
d. Once called “non-freeze coils”.
e. “Steam distributing” coils.

Answer 62

b. Controlling the face velocity of the air flowing over coils.

Question 63

Air venting is required for which of the following reasons?

a. To assure adequate water distribution in supply and return lines.
b. To assure adequate air distribution in supply lines.
c. To assure adequate air distribution in return lines.
d. To maintain face velocity.
e. All of the above.

Answer 63

a. To assure adequate water distribution in supply and return lines.

Question 64

Which of the following statements about water coils is false?

a. Coils should be hooked up in a counter flow arrangement.
b. The bottom connection should always be the water inlet.
c. Adequate air velocity over the finned surface must be maintained.
d. Circuiting should minimise the performance of the water flow vs. the pressure drop through the coil.
e. Coils need to be able to vent air.

Answer 64

d. Circuiting should minimise the performance of the water flow vs. the pressure drop through the coil.

Question 65

With counter flow arrangement of air and water:

a. The water supply connection is on the same side as the entering air.
b. The heat transfer efficiency is the same as with parallel arrangement of air and water.
c. The water supply connection is on the same side as the leaving air.
d. The water return connection is on the same side as the leaving air.
e. It decreases the heat transfer efficiency.

Answer 65

c. The water supply connection is on the same side as the leaving air

Question 66

Rippled-finned surface type coils:

a. Are often used for low temperature application where ice may form.
b. Decrease the heat transfer efficiency.
c. Increase the heat transfer efficiency by creating more turbulence at fin surfaces.
d. Have no effect on heat transfer efficiency.
e. Are not used in air handling systems

Answer 66

c. Increase the heat transfer efficiency by creating more turbulence at fin surfaces

Question 67

To assure proper air venting, the:

a. Return water connection should be at the bottom of the coil.
b. Supply water connection should be at the bottom of the coil.
c. Supply water connection should be at the top of the coil.
d. Vent should be located at the lowest points of the supply and return lines, and of the coils.
e. Double serpentine water coil circuit should be used.

Answer 67

b. Supply water connection should be at the bottom of the coil.

Question 68

A factor limiting the number of fins that can be used on coils is the:

a. Diameter of the tube.
b. Temperature of the fluid in the tube.
c. Material that the tube is made of.
d. Resistance to airflow.
e. Direction the fluid is flowing in the tube.

Answer 68

d. Resistance to airflow

Question 69

To obtain full rated capacity of water coils what should be done?

a. Connect the water supply for counter flow.
b. Connect the water supply for parallel flow.
c. Decrease the number of fins per unit length of coil.
d. Connect the coils with a staggered tube design.
e. Increase face velocity.

Answer 69

a. Connect the water supply for counter flow.

Question 70

Double serpentine water coil circuiting is used:

a. In applications requiring low water velocities and low water pressure drops.
b. Where the water velocity in the tubes is more than 2.4 m/s.
c. For any water velocity in the tubes.
d. Where the water velocity in the tubes is between 0.3 and 2.4 m/s.
e. Where the water velocity in the tube is less than 0.3 m/s.

Answer 70

b. Where the water velocity in the tubes is more than 2.4 m/s.

Question 71

Fin surface area is called:

a. Primary surface area.
b. Secondary surface area.
c. Tube surface area.
d. Heater surface area.
e. None of the above

Answer 71

b. Secondary surface area.

Question 72

The most commonly used types of water coil circuiting are:

a. Single serpentine, double serpentine, and half serpentine.
b. Full circuit, double circuit, and triple circuit.
c. Single serpentine, double serpentine, and triple serpentine.
d. Parallel and serpentine.
e. Parallel, counter flow, and serpentine.

Answer 72

a. Single serpentine, double serpentine, and half serpentine

Question 73

Proper performance of heating and cooling water coils depends on:

a. Adequate air velocity over the finned surface.
b. Counter flow arrangement of air and water.
c. Air venting from the system and the coil.
d. Tube circuiting and fins.
e. All of the above

Answer 73

e. All of the above.

Question 74

Finned tube coils in air handling systems are often called:

a. Fish coils.
b. Bare tube soils.
c. Extended surface coils.
d. Cooling coils.
e. Heating coils.

Answer 74

c. Extended surface coils.

Question 75

Fin spacing of 1.814 to 6.35 mm is most normally used in which of the following cases?

a. Direct expansion coils for low temperature applications.
b. Steam and hot water heating coils.
c. Chilled water, cooling coils.
d. Cooling refrigerant coils.
e. Refrigerant condenser coils.

Answer 75

b. Steam and hot water heating coils

Question 76

Single serpentine water coil circuiting is used:

a. In applications requiring high water velocities and low water pressure drops.
b. Where the water velocity in the tubes is more than 2.4 m/s.
c. For any water velocity in the tubes.
d. Where the water velocity in the tubes is between 0.3 and 2.4 m/s.
e. Where the water velocity in the tubes is less than 0.3 m/s.

Answer 76

d. Where the water velocity in the tubes is between 0.3 and 2.4 m/s.

Question 77

Half serpentine water coil circuiting is used:

a. In applications requiring high water velocities and low water pressure drops.
b. Where the water velocity in the tubes is more than 2.4 m/s.
c. Where the water velocity in the tubes is between 0.3 and 2.4 m/s.
d. Where the water velocity in the tubes is less than 0.3 m/s.
e. For any water velocity in the tubes

Answer 77

d. Where the water velocity in the tubes is less than 0.3 m/s.

Question 78

Two types of modern coils used for heating and cooling services in air handling systems are:

a. The continuous-plate finned surface and the spiral-finned surface.
b. The bare tube and the spiral-finned surface.
c. The continuous-plate finned surface and the bare tube.
d. The bare tube and the insulated tube.
e. None of the above.

Answer 78

a. The continuous-plate finned surface and the spiral-finned surface.

Question 79

Flat-finned surface type coils are normally used for:

a. Steam heating purposes.
b. Water heating purposes.
c. High temperature application.
d. Low temperature application where ice may form.
e. Greater turbulence of air at the fin surface.

Answer 79

d. Low temperature application where ice may form

Question 80

To prevent freezing of downstream equipment in a coil handling a large amount of out door air, which of the following is required?

a. A long coil length.
b. A vacuum breaker.
c. A preheat coil.
d. An oversized coil.
e. Two-Position damper motor

Answer 80

c. A preheat coil

Question 81

The use of ethylene glycol solution will result in which of the following:

1. Lower heat transfer rate.
2. Better protection against freezing.
3. Increased friction losses in the coil and piping.
4. The requirement of a larger pump with more horsepower.
   a. 1, 4
   b. 1, 3
   c. 2, 4
   d. 3
   e. 1, 2, 3, 4

Answer 81

e. 1, 2, 3, 4.

Question 82

Steam coils with long tube lengths:

a. Have the greatest freezing problems at extremely low temperatures such as -35° C.
b. Have the greatest freezing problems at temperatures of about –2° C to –1° C.
c. Have freezing problems at any temperature.
d. Are less likely to freeze than steam coils with short tube lengths.
e. Are not likely to freeze at any temperature

Answer 82

b. Have the greatest freezing problems at temperatures of about –2° C to –1° C.

Question 83

Which of the following steam traps are preferred for use with steam coils operating at low and medium steam pressure?

a. Inverted bucket.
b. Dynamic.
c. F & T trap, float and thermostatic.
d. Thermostatic only.
e. None of the above.

Answer 83

c. F & T trap, float and thermostatic

Question 84

Freezing problems in steam coils with long tube lengths, handling a large amount of low temperature outside air are:

a. Minimised by using preheat coils controlled by an outdoor temperature controller.
b. Minimised by using modulating control valves to control the steam heating coil output.
c. Best minimised by using a two-position control valve to control coil output.
d. Minimised by using an oversized coil.
e. Minimised by using an oversized control valve

Answer 84

a. Minimised by using preheat coils controlled by an outdoor temperature controller

Question 85

A thermostat that is sometimes installed in the return air duct serves which main function?

a. To limit temperature of the heated outside air.
b. To control the throttle of the steam in the tubes.
c. To sense the temperature of the steam in the coils.
d. To minimise temperature fluctuations in discharge air.
e. To heat recirculated air

Answer 85

d. To minimise temperature fluctuations in discharge air.

Question 86

The greatest fears in hot water coil installations handling subfreezing air are:

1. Pipe expansively.
2. Outside air temperature being too low.
3. The failure of the circulating pump.
4. Water viscosity being too high.
5. The failure of the heat source.
   a. 1, 2, 4
   b. 1, 2, 3
   c. 3
   d. 1, 4, 5
   e. 3, 5

Answer 86

e. 3, 5.

Question 87

For a glycol system using hot water as its heat source which of the following statements is false?

a. The hot water supply valve will be opened to feed a constant flow of hot water to the converter.
b. Provide flanges or unions and manual shutoff valves to facilitate coil removal.
c. The temperature controller opens the hot water supply valve when the temperature outside drops to 10° C.
d. The flow switch automatically starts the glycol pump automatically after the hot water supply valve is opened.
e. Hot water temperature should not exceed 100° C.

Answer 87

d. The flow switch automatically starts the glycol pump automatically after the hot water supply valve is opened.

Question 88

The purpose of a vacuum breaker used with steam coils is to:

a. Prevent freezing caused by a vacuum or negative pressure in the steam coil.
b. Ensure negative air pressure in the conditioned space.
c. Prevent excessive temperatures within the steam coil.
d. Ensure proper operation of the steam control valve.
e. Ensure positive air pressure in the conditioned space.

Answer 88

a. Prevent freezing caused by a vacuum or negative pressure in the steam coil.

Question 89

It is good design practice to select a steam coil size so that:

a. 100% of the coil capacity is needed when the air temperature entering the coil is –1° C.
b. At least 40% of the coil capacity is needed when the air temperature entering the coil is –1° C.
c. At least 80% of the coil capacity is needed when the air temperature at the coil inlet is –1° C.
d. At least 10% of the coil capacity is needed when the air temperature at the coil inlet is –5° C.
e. It is twice the size that is required to handle the heating load

Answer 89

b. At least 40% of the coil capacity is needed when the air temperature entering the coil is –1° C.

Question 90

Which of the following is not a cause of freezing in hot water coils?

a. Failure of the circulating pump
b. Very low circulating water velocity
c. Very high circulating water velocity
d. Failure of the heat source
e. Poor air venting of the coil.

Answer 90

c. Very high circulating water velocity

Question 91

To prevent freezing of the steam coil when steam pressure at the coil inlet is too low or is lost:

a. A second preheat coil is installed at the outside air inlet.
b. A modulating steam control valve is installed at the coil inlet.
c. A two-position steam control valve is installed at the coil inlet.
d. Provisions are made to stop the fan and close the outdoor air dampers.
e. The fan output is increased

Answer 91

d. Provisions are made to stop the fan and close the outdoor air dampers

Question 92

Glycol coils using ethylene glycol:

a. Are used only for heating purposes and are not used for cooling purposes.
b. Are not recommended for use in heating and air conditioning systems in the food industry.
c. Use direct fired boilers as their heat source.
d. Do not use steam-glycol converters as their heat source.
e. Give reasonable heat transfer efficiency at low glycol velocity

Answer 92

b. Are not recommended for use in heating and air conditioning systems in the food industry

Question 93

Which of the following statements about vacuum breakers is false?

a. They are used to prevent freeze-ups caused by negative pressure in the coil.
b. The vacuum breaker must be installed before the control valve and as near as possible to the outlet connection of the coil.
c. Check valves used as vacuum breakers may be left open to the atmosphere.
d. Check valves used as vacuum breakers may be connected to the return header.
e. Vacuum breakers are essential for satisfactory functioning of the steam trap.

Answer 93

b. The vacuum breaker must be installed before the control valve and as near as possible to the outlet connection of the coil.

Question 94

It is good practice to select steam coils which require at least 40% of coil capacity when air temperature is -1° C for which of the following reasons?

a. Steam flow is high enough at high temperature and prevents build-up and freezing of condensate.
b. The load on the circulating fan is kept from overheating.
c. The mixing valve will never cut out if capacity stays above 40%.
d. To avoid hot condensate splashing.
e. None of the above.

Answer 94

a. Steam flow is high enough at high temperature and prevents build-up and freezing of condensate.

Question 95

Steam coils with a short tube length of 1.1 m or less are:

a. More likely to freeze, even if the steam trap is properly chosen.
b. Less likely to freeze regardless of steam trap choice and coil piping.
c. More likely to freeze, even if the coil is properly piped and sloped.
d. Less likely to freeze if the steam trap is properly chosen and the coil is properly piped.
e. Not recommended because they are more likely to freeze

Answer 95

d. Less likely to freeze if the steam trap is properly chosen and the coil is properly piped.

Question 96

The flow arrangement best suited for hot water coils used to heat sub-freezing air is:

a. The counter flow arrangement because it is more efficient.
b. The parallel flow arrangement because it gives better protection against freezing.
c. One in which the cold air enters the coil where the coldest water is flowing.
d. The half serpentine.
e. The triple bypass flow arrangement.

Answer 96

b. The parallel flow arrangement because it gives better protection against freezing.

Question 97

In a hot water coil which of the following is not included for providing a good guideline for the correct application of the system with minimal possibility of freeze-up?

a. Positive air venting of the coil is essential.
b. The air velocity should exceed 10 m/s.
c. The water temperature should be maintained at a reasonable pre-set temperature.
d. The water velocity should exceed 0.8 m/s.
e. A constant flow of water should be fed to the coil.

Answer 97

b. The air velocity should exceed 10 m/s.

Question 98

The purpose of the flow switch or sail switch used with hot water coils is to:

a. Stop the fan and close the outside air dampers if the low limit temperature controller malfunctions or the heat source fails.
b. Open the outside air dampers wide when the outside air temperature rises.
c. Increase the heat source temperature if the outside air temperature decreases.
d. Close the outside air dampers and stop the fan if the flow of water is interrupted due to pump failure or closing of the hand valves.
e. Increase the hot water flow through the coil if the outside air temperature is too low.

Answer 98

d. Close the outside air dampers and stop the fan if the flow of water is interrupted due to pump failure or closing of the hand valves.

Question 99

A modulating control valve:

a. Is not used to control steam coils at any air inlet temperature.
b. Is used for steam coils where the condensate is lifted to an overhead return.
c. Is used for steam coils when the entering air temperature is below 1.5° C.
d. Can be used to control steam coils when the entering air temperature is above 1.5° C.
e. Can be oversized

Answer 99

d. Can be used to control steam coils when the entering air temperature is above 1.5° C.

Question 100

The inverted bucket steam trap is:

a. Used when the coil steam pressure is higher than 172 kPa or 25 psig.
b. Used when the flow is modulated.
c. Used when the coil steam pressure is lower than 172 kPa or 25 psig.
d. Recommended when condensate flows by gravity into a return main at atmospheric pressure.
e. More expensive than the F & T trap.

Answer 100

a. Used when the coil steam pressure is higher than 172 kPa or 25 psig.

Question 101

The purpose of the “freeze-stat” temperature controller used with hot water coils is to:

a. Close the outside air dampers and stop the fan if the heat source fails or the low limit temperature controller malfunctions.
b. Increase the hot water flow through the coil if outside air temperature is too low.
c. Increase the heat source temperature if the outside air temperature decreases.
d. Open the outside air dampers wide when the outside air temperature rises.
e. Increase the fan output if the return air temperature is too low.

Answer 101

a. Close the outside air dampers and stop the fan if the heat source fails or the low limit temperature controller malfunctions

Question 102

Which of the following is not an installation recommendation for steam traps?

a. Base steam trap selection on the pressure difference across the trap and a minimum capacity corresponding to three times the coil condensate rate.
b. Locate the steam trap so that its outlet is at least 30 cm above the coil return connection.
c. Trap each coil separately.
d. Drip the steam supply main through a steam trap into the return condensate main.
e. Install a strainer near the inlet of each trap.

Answer 102

b. Locate the steam trap so that its outlet is at least 30 cm above the coil return connection

Question 103

Steam coils:

a. Should be installed with tubes in a vertical position to ensure positive condensate drainage.
b. When installed in the horizontal position, do not have to be pitched toward the return.
c. Are installed exactly the same as are glycol coils.
d. Do not require a vacuum breaker.
e. Do not require air venting

Answer 103

a. Should be installed with tubes in a vertical position to ensure positive condensate drainage.

Question 104

Steam coil piping and trapping:

a. Is the same for hot water and glycol coils.
b. Only handles steam and non-condensable gases.
c. Differs from the hot water and glycol coil because it carries more fluids: steam, air, water, and non-condensable gases.
d. Are installed in the horizontal position whenever possible.
e. Can be supported directly by the coils.

Answer 104

c. Differs from the hot water and glycol coil because it carries more fluids: steam, air, water, and non-condensable gases.

Question 105

Air vents are:

a. Not required when an inverted bucket steam trap is used.
b. Not required on the steam mains if an inverted bucket steam trap is used at the steam coil.
c. Not required at the steam coil if a float and thermostatic (F & T) trap is used at the steam coil with an atmospheric return and the steam main is adequately vented.
d. Not required anywhere if a float and thermostatic (F & T) trap is used at the steam coil.
e. Required only with hot water coils.

Answer 105

c. Not required at the steam coil if a float and thermostatic (F & T) trap is used at the steam coil with an atmospheric return and the steam main is adequately vented.

Question 106

Ethylene glycol used in glycol coils:

a. Has a higher heat transfer efficiency than hot water
b. Has less friction losses in the coil and piping than hot water
c. Requires a smaller pump and less horsepower than hot water
d. Has much lower pressure drops through the coil and piping
e. Has a lower heat transfer efficiency than hot water.

Answer 106

e. Has a lower heat transfer efficiency than hot water