6525026
Beschreibung
Quiz von Neil Revollo, aktualisiert more than 1 year ago
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Erstellt von Neil Revollo
vor fast 8 Jahre
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Frage 1
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A central station air handling unit
Antworten
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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
Frage 2
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A system that uses the space above a drop ceiling for return air is called
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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
Frage 3
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Larger fan coil units are most commonly used to condition
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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
Frage 4
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How is the airflow adjusted on most commercial air handlers?
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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
Frage 5
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Why do air handling units require field adjustment during the commissioning phase?
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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
Frage 6
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The components of a commercial fan coil unit include
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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
Frage 7
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Where are unit ventilator fan coil units installed in schools?
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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
Frage 8
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The major components of an air handling unit include
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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
Frage 9
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Immediately after making adjustments to an air handler, it is important to check
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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
Frage 10
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What advantage do hot water heating coils have over steam heating coils?
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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
Frage 11
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Why does a chilled water cooling coil have more rows of coils than a hot water heating coil?
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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
Frage 12
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Hot water heating coils should be piped
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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
Frage 13
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What happens if the steam trap at the outlet of a heating coil is stuck in the closed position?
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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
Frage 14
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The advantage of the backward curved centrifugal fan over the forward curved centrifugal fan is that
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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
Frage 15
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The two main types of fan drives are
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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
Frage 16
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The most common fan used for moving air through ductwork in residential air conditioning is
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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
Frage 17
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The most common fan used for moving air across outdoor condenser coils in residential air conditioning is
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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
Frage 18
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What is an "air-over" motor?
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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
Frage 19
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After making a belt or pulley adjustment to a belt drive fan, it is crucial to check
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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
Frage 20
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The best way to remove a belt from a belt drive is to
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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
Frage 21
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What are the advantages of backward curved air foil centrifugal fan blades?
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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
Frage 22
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The two basic types of fans used in most air handling units are
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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
Frage 23
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Three types of fan blades used with centrifugal fans include
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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
Frage 24
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The three common types of axial fans are
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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
Frage 25
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A type of fan that is designed for producing high static pressure in a duct distribution system is:
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Condenser
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Impeller
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Axial
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Centrifugal
Frage 26
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This type of fan is commonly used on condenser motors because it moves high volumes of air in low static conditions:
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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
Frage 27
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The amp draw of a propeller fan will ________ if the airflow leaving the blower is blocked or restricted.
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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
Frage 28
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The two broad types of fan designs are
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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
Frage 29
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If the air inlet to a centrifugal fan is restricted
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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
Frage 30
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When is a forward curved centrifugal blower motor most likely to draw high amps?
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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
Frage 31
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Airflow through an axial fan is
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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
Frage 32
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Axial fans are commonly used on applications where
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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
Frage 33
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Compared to a centrifugal fan, an axial fan is generally
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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
Frage 34
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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.
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Increase by 10%
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Double
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Triple
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Increase by 25%
Frage 35
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What is the RPM of a fan that uses a 4 inch motor pulley, 8 inch fan pulley, and a motor RPM of 1750?
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750
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500
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1250
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875
Frage 36
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In order to double fan RPM, the motor horsepower
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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)
Frage 37
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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?
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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
Frage 38
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AMCA fan performance classifications are based on
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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
Frage 39
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What fan performance characteristics are shown on a typical fan curve?
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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
Frage 40
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To use a fan curve, you need to know
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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
Frage 41
Frage
Why should ultraviolet germicidal lamps not be handled with bare hands?
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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
Frage 42
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What is a HEPA filter?
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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
Frage 43
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Which of the following filters would be appropriate for a large industrial air handler?
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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
Frage 44
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What is the difference between a viscous impingement filter and a standard filter?
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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
Frage 45
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To minimize the buildup of dangerous levels of static electricity in industrial processes, industrial air conditioning systems often have provisions for
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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
Frage 46
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Poorly maintained humidifiers can become indoor air quality concerns because of
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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
Frage 47
Frage
The steam grid humidifier works by
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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
Frage 48
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Types of humidifiers used with commercial air handling equipment include
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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
Frage 49
Frage
The economizer on a commercial packaged air conditioning system
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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
Frage 50
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What is the function of an energy recovery unit?
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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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