6525026
Descrição
Quiz por Neil Revollo, atualizado more than 1 year ago
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Criado por Neil Revollo
quase 8 anos atrás
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Questão 1
Questão
A central station air handling unit
Responda
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Consists of a fan and coil and usually handles a single room or zone
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Is used instead of a fan and fan motor
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Combines the functions of the evaporator blower and the condenser blower
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Is used for large systems and is assembled on site using separate components
Questão 2
Questão
A system that uses the space above a drop ceiling for return air is called
Responda
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a drop ceiling return system
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a spatial air distribution system
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an extended plenum system
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a static regain system
Questão 3
Questão
Larger fan coil units are most commonly used to condition
Responda
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Factories
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Offices and stores where common air distribution is feasible
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Schools
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Hotel and motel rooms
Questão 4
Questão
How is the airflow adjusted on most commercial air handlers?
Responda
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By increasing or decreasing the voltage to the fan motor
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By adjusting the pitch of the blades on the blower wheel
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By moving the speed tap on the blower motor
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By adjusting the sheave on an adjustable pulley
Questão 5
Questão
Why do air handling units require field adjustment during the commissioning phase?
Responda
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Manufacturing errors that affect blower performance are common
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To match the blower performance to the system requirements
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Because the performance requirements of the blower cannot be determined in advance
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Air handling units normally do not require field adjustment
Questão 6
Questão
The components of a commercial fan coil unit include
Responda
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A compressor, condenser, metering device, and evaporator
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A fan, compressor and condenser
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A fan and electric strip heaters
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A fan, a water coil, a filter, a fresh air supply, and a control system
Questão 7
Questão
Where are unit ventilator fan coil units installed in schools?
Responda
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Outside each classroom on a concrete pad
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On the roof above each classroom
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In the school mechanical room
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Below window level in each classroom
Questão 8
Questão
The major components of an air handling unit include
Responda
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Air compressor, water separator, and air tank
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Compressor, evaporator, and condenser
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Heating and cooling coils and electric heat strips
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Fan and motor, heating and cooling coils, air filter, dampers
Questão 9
Questão
Immediately after making adjustments to an air handler, it is important to check
Responda
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The compressor shell temperature
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The return air temperature
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The blower motor amp draw under load
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The outdoor ambient temperature
Questão 10
Questão
What advantage do hot water heating coils have over steam heating coils?
Responda
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They operate at a higher temperature than stem heating coils
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They produce more heat
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Hot water coils can be smaller than steam heating coils
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They are easier to control
Questão 11
Questão
Why does a chilled water cooling coil have more rows of coils than a hot water heating coil?
Responda
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hot water heating coils can take advantage of radiant heat transfer and cooling coils cannot
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most buildings require more cooling than heating
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heat does not travel into cold water as readily as it does into hot water
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more surface is necessary for dehumidification
Questão 12
Questão
Hot water heating coils should be piped
Responda
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for parallel flow so that the warmest water meets the coldest air
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for counter flow so that the warmest water meets the warmest air
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with iron pipe for durability and strength
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with PVC pipe to take advantage of PVC's natural insulating ability
Questão 13
Questão
What happens if the steam trap at the outlet of a heating coil is stuck in the closed position?
Responda
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steam flow through the coil will be excessive and air temperatures will be too high
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steam flow through the coil will stop and the air temperature will be too low
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the steam coil will flood with condensate water
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the boiler will stop producing steam
Questão 14
Questão
The advantage of the backward curved centrifugal fan over the forward curved centrifugal fan is that
Responda
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backward curved fans operate at lower RPMs
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backward curved fans are normally quieter in operation
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backward curved centrifugal fans are well suited for small airflow quantities
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backward curved fans are non-overloading
Questão 15
Questão
The two main types of fan drives are
Responda
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Planetary gear drive and worm gear drive
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Direct drive and belt drive
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Magnetic drive and hydrodrive
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Serpentine belt and chain drive
Questão 16
Questão
The most common fan used for moving air through ductwork in residential air conditioning is
Responda
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Propeller
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Forward curved centrifugal
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Vane axial
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Backward curved centrifugal
Questão 17
Questão
The most common fan used for moving air across outdoor condenser coils in residential air conditioning is
Responda
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Forward curved centrifugal
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Vane axial
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Propeller
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Backward curved centrifugal
Questão 18
Questão
What is an "air-over" motor?
Responda
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A motor that is designed for units with the fan located at the top of the unit
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A motor that is cooled by airflow over the motor
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A motor that is designed to be installed on the bottom of a fan unit
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A motor whose function is to blow air over the fan motor to cool it
Questão 19
Questão
After making a belt or pulley adjustment to a belt drive fan, it is crucial to check
Responda
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the fan motor operating current reading
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the resistance of the motor winding insulation with a megohm meter
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the resistance of the motor windings
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the level of the blower housing
Questão 20
Questão
The best way to remove a belt from a belt drive is to
Responda
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Roll the belt over the edge of the larger pulley
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Roll the belt over the edge of the smaller pulley
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Remove the drive pulley from the motor
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Loosen the mount on the drive pulley to create slack in the belt
Questão 21
Questão
What are the advantages of backward curved air foil centrifugal fan blades?
Responda
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Fans with backward curved blades generally operate at lower RPMs
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The air foil shaped blades result in less turbulence and noise
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backward curved centrifugal fans are well suited for small airflow quantities
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The air foil shaped blades are less expensive
Questão 22
Questão
The two basic types of fans used in most air handling units are
Responda
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reciprocating and orbital
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centrifugal and axial
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positive pressure and negative pressure
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clockwise rotating and counter clockwise rotating
Questão 23
Questão
Three types of fan blades used with centrifugal fans include
Responda
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Concentric, isentropic, and exothermal
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Straight, forward curved , and right angle
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Forward curved, backward curved, and backward curved airfoil
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Straight, right angle, and airfoil
Questão 24
Questão
The three common types of axial fans are
Responda
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Box fan, window fan, and oscillating
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Propeller, vane axial and tube axial
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Clockwise, counterclockwise, and oscillating
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Forward curved, backward curved, and propeller
Questão 25
Questão
A type of fan that is designed for producing high static pressure in a duct distribution system is:
Responda
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Condenser
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Impeller
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Axial
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Centrifugal
Questão 26
Questão
This type of fan is commonly used on condenser motors because it moves high volumes of air in low static conditions:
Responda
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Propeller
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Forward-curved centrifugal
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Backward-curved centrifugal
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Tube axial
Questão 27
Questão
The amp draw of a propeller fan will ________ if the airflow leaving the blower is blocked or restricted.
Responda
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Amp draw cannot be determined on a propeller fan
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Decrease
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Not change
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Increase
Questão 28
Questão
The two broad types of fan designs are
Responda
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Forced draft and induced draft
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Forward curved and backward curved
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Centrifugal and axial
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Propeller and squirrel cage
Questão 29
Questão
If the air inlet to a centrifugal fan is restricted
Responda
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The fan operation will be unaffected
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The fan RPM will decrease
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The fan motor current draw will increase
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The fan motor current draw will decrease
Questão 30
Questão
When is a forward curved centrifugal blower motor most likely to draw high amps?
Responda
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when the motor RPM is set lower than the manufacturer's specifications
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when there is no restriction to the airflow in or out of the blower
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when the airflow leaving the blower is restricted
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when the airflow to the blower is restricted
Questão 31
Questão
Airflow through an axial fan is
Responda
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From the inside of the fan blade outwards in a radial pattern
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At a 45° angle to the fan shaft
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Parallel to the fan shaft
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Perpendicular to the fan shaft
Questão 32
Questão
Axial fans are commonly used on applications where
Responda
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large volumes of air are required at a relatively high static pressure
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Reverse loading of the blower bearings is desired
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large volumes of air are required at a relatively low static pressure
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small volumes of air are required at a relatively high static pressure
Questão 33
Questão
Compared to a centrifugal fan, an axial fan is generally
Responda
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About the same noise level
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Noisier at low volumes and quieter at high volumes
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Quieter
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Noisier
Questão 34
Questão
Technicians should know that fan speed is directly related to the amount of air a fan can move; therefore, doubling the fan speed will ________ the amount of air flow.
Responda
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Increase by 10%
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Double
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Triple
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Increase by 25%
Questão 35
Questão
What is the RPM of a fan that uses a 4 inch motor pulley, 8 inch fan pulley, and a motor RPM of 1750?
Responda
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750
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500
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1250
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875
Questão 36
Questão
In order to double fan RPM, the motor horsepower
Responda
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Must increase by a factor of 4 (2 × 2)
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Will not be affected by the fan RPM
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Must also double
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Must increase by a factor of 8 (2 × 2 × 2)
Questão 37
Questão
What speed will a fan turn if the drive motor is turning at 1250 RPM, the motor pulley is 4 inches in diameter, and the fan pulley is 8 inches in diameter?
Responda
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2500 RPM
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1250 RPM
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625 RPM
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The fan RPM cannot be determined using this information
Questão 38
Questão
AMCA fan performance classifications are based on
Responda
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the minimum and maximum motor horsepower
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Minimum and maximum fan RPM for the design airflow
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The upper and lower ranges of static pressure and outlet velocity
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The physical design of the fan wheel
Questão 39
Questão
What fan performance characteristics are shown on a typical fan curve?
Responda
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pressure drop, efficiency, and horsepower
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RPM, tip speed, and horsepower
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sound levels, bearing temperatures, and reluctance
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horsepower, RPM, and reluctance
Questão 40
Questão
To use a fan curve, you need to know
Responda
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the horsepower and efficiency
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the CFM and the RPM
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the RPM and tip speed
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the required CFM and the static pressure the fan must operate against
Questão 41
Questão
Why should ultraviolet germicidal lamps not be handled with bare hands?
Responda
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The oil from your fingerprints can lead to premature failure of the lamp
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The coating on the outside of the lamps is toxic
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The exterior UV coating will wipe off, reducing the UV output
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The residual UV in the lamp coatings can cause severe burns
Questão 42
Questão
What is a HEPA filter?
Responda
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a filter for heated pans
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a filter for a steam heating coil
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a very high efficiency air filter
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a high efficiency water filter
Questão 43
Questão
Which of the following filters would be appropriate for a large industrial air handler?
Responda
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an electronic air cleaner
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a washable hogs hair filter
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a 16" × 20" × 1" panel filter
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a large fiberglass roll filter
Questão 44
Questão
What is the difference between a viscous impingement filter and a standard filter?
Responda
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viscous filters are tested for viscosity
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viscous filters are specifically for filtering oil
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viscous filters are treated with a sticky substance to trap and hold dirt
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viscous filters use an electrical charging system
Questão 45
Questão
To minimize the buildup of dangerous levels of static electricity in industrial processes, industrial air conditioning systems often have provisions for
Responda
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Humidification
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Grounding the air conditioning cabinet
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Arc arrestors
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High level electromagnetic radiation pulse control to reduce static
Questão 46
Questão
Poorly maintained humidifiers can become indoor air quality concerns because of
Responda
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increased static discharge around all electrical connections
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mold and mildew growth
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increased outgassing of volatile organic compounds
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unintended chemical reactions with HFC refrigerants
Questão 47
Questão
The steam grid humidifier works by
Responda
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Introducing live steam into the air stream through a grid of orifices
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Spraying water through nozzles and atomizing it to steam
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Passing air over a wetted element
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Boiling water in a pan to steam
Questão 48
Questão
Types of humidifiers used with commercial air handling equipment include
Responda
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steam grid, steam pan, and direct water spray
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direct expansion, steam, and hot water
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bypass, atomizing, and wetted media
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direct expansion, chilled water, and steam
Questão 49
Questão
The economizer on a commercial packaged air conditioning system
Responda
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Reduces the indoor blower speed during peak loads to produce cooler air and save energy
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Reduces the voltage to the compressor during peak loads to save power
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Limits the operating cycles of the system to no more than 15 minutes
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Uses outdoor air to provide cooling at low ambient temperatures
Questão 50
Questão
What is the function of an energy recovery unit?
Responda
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To use waste heat for on-site power generation
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To recover energy used to cool electric motors
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To exchange heat between outdoor air being introduced for ventilation and exhaust air
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To recover waste heat from a combustion process
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