air_water_balancing_20121208193547 Flashcards
2
Q
A vertical line on the psychometric chart between two points at constant dry bulb temperature represents change in _____ _____
A
LATENT HEAT
3
Q
In the formula “E=IR”, I represents _____
A
AMP/CURRENT
4
Q
A direct acting controller will increase the output as the control ______ ______
A
VARIABLE INCREASES
5
Q
Three basic types of fans are used in the HVAC system are the ______ fan or _____, the ______ flow fan, and special designs using fans and blowers in different housings.
A
CENTRIFUGAL and BLOWERAXIAL
6
Q
A terminal box commonly integrates a sound champed to reduce noise generated within it is called a sound _______
A
ATTENUATOR
7
Q
The ______ of the centrifugal pump varies directly with the impeller diameter.
A
VOLUME
8
Q
The four basic types of controls systems for HVAC are ______,______,______,and______
A
ELECTRIC, ELECTRONIC, PNEUMATIC, SELF CONTAINED
9
Q
- The three basic categories of fluid properties that are important to TAB technicians are:_______, _____ ______ and specific volume relationships, and _____ _____.
A
COMPRESSIBILITY, WEIGHT, DENSITY AND VOLUME, AND SPECIFIC HEAT.
10
Q
- Two types of motor starters are usually used with induction motors are _____ _____ and _______ ______.
A
FULL VOLTAGE, MAGNETIC STARTERS
11
Q
Vertical blades on grilles spread the air _______
A
HORIOZONTALLY
12
Q
- Air systems may be classified into two basic categories:
A
SINGLE PATH SYSTEMS, DUEL PATH SYSTEMS
13
Q
- U-Tube manometers should be used for reading under ____ ____
A
1.0” WG
14
Q
- A horizontal line on the ______ chart between two points with a constant dew point temperature represents a change in
A
PSYCHOMETRIC, SENSIBLE HEAT
15
Q
______ controls do not use an external source of power but develop their own power.
A
SELF-CONTAINED
16
Q
- The three variations of the centrifugal fan used in HVAC work is ______ _____, ______, ______ and air foil.
A
FORWARD CURVED, BACKWARD, AND INCLINED
17
Q
- If the pump speed can be changed, the volume of liquid that is pumped will vary ______ as the speed.
A
DIRECTLY
18
Q
- The factors that include only the effect of the system configuration on the fans performance are called ______ ______.
A
SYSTEM EFFECT
19
Q
- In the sample specification, the TAB technician must adjust each register, diffuser, and terminal unit to handle and properly distribute the designed airflow within +/- ____ of the specified quantities.
A
10%
20
Q
- The amount of heat contained within an object varies with the object’s _______, ______ and ______.
A
TEMPERATURE, MASS, AND SUBSTANCE
21
Q
The most common speed for motors is _____ rpm & _____ rpm.
A
1800 & 3600 RPM
22
Q
______ head is the pressure of the pumped liquid which represents system resistance that must be overcome.
A
FRICTION
23
Q
The ______ is the standard in the industry for air flow measuring instruments.
A
MANOMETER
24
Q
Humidification and dehumidification are both _____ heat processes
A
LATENT
25
Q
Control systems are considered _____ as long as each increment of the controlled variable produces the same _____ of signal.
A
LINEAR, INCREMENT
26
A _____ terminal box adds sensible heat to the supply air and is one of its main functions.
REHEAT
27
The horsepower required of a ______ pump varies directly as the _____ of the diameter of the impeller.
CENTRIFUGAL CUBE
28
________ is the study of the _______ properties of moist air and the application of these properties to the environment and the environmental systems.
PSYCHOMETRICS, THERMODYNAMICS
29
A variable air volume system controls the dry bulb temperature within a space by vary the ______ of ______ _____ rather than the supply _________.
VOLUME, SUPPLY AIR, TEMPERATURE
30
In hydronic systems ______ head is ignored because its value usually is insignificant.
VELOCITY
31
The _________ ______ _______ of a fan is the area in the effective duct length on the outlet of the fan that causes the fan to perform less efficiently because of the changes in the velocity profile.
NON-UNIFORM, OUTLET VELOCITY,
32
It is strongly advised that inlet elbows be installed at least _____ duct diameters away from any axial fan inlet.
THREE
33
_____ ______ _____ volume dampers should be located in branch ducts where the total estimated static pressure is less than ___ inch. W.G.
SINGLE LEAF TYPE, 0.5" WG
34
The _____ pump type is normally used in HVAC systems to produce ____.
CENTRIFUGAL, FLOW
35
A ______ is a dry type ______ operated differential pressure gage used for measuring extremely ______ & ______ differential pressures.
MAGNEHELIC, DIAPHRAGM, SENSITIVE & ACCURATE
36
______ is the science of heat energy and its ______ to & from other forms of energy.
THERMODYNAMICS, TRANSORMATION
37
The position of a controlled device when ______ is considered the _____ position.
DE-ENGERGIZED, NORMAL
38
______ pumps with _____ _____ require some leakage to lubricate and cool the area between the packing material and the _____.
CENTRIFUGAL, PACKING GLANDS, SHAFT
39
Pumps with _____ _____ must not run dry, even for “______” to determine rotation.
MECHANICAL SEALS, BUMPING
40
Duct fitting loss coefficient “___” is a number that represents the _____ heads lost at duct transitions.
C, VELOCITY
41
40. Under some conditions for air balancing a correction for air temperature is not necessary between ___ F and ___F.
50 F 90 F
42
A fan is a _____ _____ machine and will produce the same volume of ____ ____ regardless of the air ____ being handled.
CONSTANT VOLUME, AIR FLOW, DENSIITY
43
Volume dampers are primary elements in the duct system and are used for controlling air flow rates by introducing a _____ to airflow in the system.
RESISTANCE
44
_____ terminal units use the radiant heat waves to heat the space not the air.
RADIATION
45
A _____ _____ anemometer set is made up of the meter, ____ measuring probes, two range _____, and connecting hoses.
DEFLECTING VANE, THREE, SELECTORS
46
45. SCFM stands for “_____ _____ ____ ____ _____which is “cfm” corrected to standard air conditions.
STANDARD CUBIC FEET PER MINUTE
47
For a given pump the _____ _____ as capacity increases
NPSH, INCREASES
48
If there is an ______ in a duct cross-sectional area, the velocity and velocity pressure will _____ and the _____ pressure will ______.
INCREASE, DECREASE, STATIC, INCREASE
49
48. When increasing the rpm on a fan, the fan _____ _____ will increase as the ____ of the fan rpm increases.
BRAKE POWER, CUBE
50
The standard pressure for air & water is ____” Hg.
29.92" HG
51
he standard temperature for water is ___F and for air is ___F.
68F 70F
52
51. The standard volume for water is ____ and air is ______.
.016 CUBIC FOOT LBS 13.33 CUBIC FOOT LBS
53
The standard density for water is ______ and air is _____.
62.4 lb/ft3 .075 lb/ft3.
54
The specific heat for water is _____ and air is _____ .
1.0 Btu/lb/°F.24 Btu/lb/°F
55
54. When installing fan drive systems belts speeds should not exceed ____ fpm or be less than _____ fpm.
5000 FPM1000 FPM
56
_____ is when the velocity of the primary air emerging from the supply outlet induces air movement within the room air.
ENTRAINMENT
57
Net positive _____ head is a _____ suction pressure that is to be maintained on a system to eliminate cavitation.
MINIMUM
58
The _____ of a fluid that a pump must lift on the suction side of the pump center line is called suction.
HEIGHT, LIFT,
59
One condition that can create ______ in a system is the pumped liquid is too ___.
CATIVATION, HOT
60
The _____ _____ is where the velocity pressure changes across the cross sectional area of a duct due to the friction between the conduit walls and the fluid.
VELOCITY PROFILE
61
In determining the _____ loss through a pipe tee in a system you must determine the equivalent ____ ____.
FRICTION, PIPE LENGTH
62
FAN _____ _____ power is the actual _____ required to drive the fan.
BRAKE POWER, POWER
63
To determine volume ____ ____ ____ ____ through a duct, the velocity, in fpm, is multiplied by the area of the duct section, square feet.
CUBIC FEET PER MINUTE
64
____ ____ is where the throw from diffuser discharges the jet flow near a wail or ceiling, the entrained air along the surface is minimal & the jet stream is “pulled” against the surface.
SURFACE EFFECT
65
The most common cause of reduced fan performance is the ___-______ flow into the inlet of the fan.
NON-UNIFORM
66
The _____ head is the pressure that is required to raise the pumped liquid from its static head to the dynamic discharge head in an open system.
INDEPENDENT
67
66. If a rectangular duct is used in place of a round duct with the same cross section area as the round duct the velocity and friction loss will _____ for a given air flow.
INCREASE
68
67. Pressure in an HVAC system is the force required to overcome the friction and ____ losses of the system.
DYNAMIC
69
To achieve accurate duct velocity measurements the reading must be taken __ to __ duct diameters downstream from the object causing the turbulence.
3 TO 20
70
Velocity pressure can be determined by subtracting the _____ pressure from the ____ pressure in the duct.
STATIC, TOTAL
71
70. Variable air volume systems can be accomplished in constant volume systems by incorporating _____ VAV boxes
BYPASS
72
The _____ _____, when used with a gage, manometer, or micro-manometer is preferred over every other method for field measurement of air velocity, system total air, outdoor air return air, fan static pressure, fan total pressure and fan outlet velocity pressure.
PITOT TUBE
73
A _____ should be provided on the steam supply side of a control valve to protect the ____.
STRAINER, VALVE
74
The operation of a thermal type ______ depends on the fact that the ______ of a heated wire will change with its temperature.
ANEMOMETER, RESISTANCE
75
Dynamic losses in an HVAC system can be expressed as a _____ _____ or by the equivalent length of straight duct which has the same ____ magnitude.
LOSS COEFFICIENT, LOSS
76
75. A flow measuring hood determines the velocity of the air from terminal units & gives a direct reading in ___.
CFM
77
One of the factors that may help avoid system effect in a fan system is better fan and system ____ connections.
DUCT
78
____ is where dirt particles held in suspension in the secondary air are subjected to turbulence at the face of an outlet & are deposited on the ceiling.
SMUDGING
79
____ ____ of a refrigeration compressor is the rapid _____ & _____ of the compressor.
SHORT CYCLING, STARTING AND STOPPING
80
79. The expected air velocity within an occupied space is ___ FPM
50 FPM
81
80. The temperature at which a substance has no molecular action is ____ F and is called “____ ____”.
ABSOLUTE ZERO, -460F
82
The _____ _____ for a grill is the ratio of the blade depth to the grill opening.
BLADE RATIO
83
The real evaluation of air distribution in a space is when the occupants are ______.
COMFORTABLE
84
One of the two categories of fan assisted terminal air boxes is the constant volume box where all air delivered to the space passes through the blower at a ____ _____.
CONSTANT VOLUME
85
In a _____ return two-pipe system the return main flow direction is the _____ of the supply main flow and the return water from each unit takes the shortest path back to the boiler.
DIRECT, OPPOSITE
86
In sizing the main duct using the equal friction design method, you start with the _____ desired.
VELOCITY
87
86. On the psychometric chart the reason the Btuh for enthalpy is always greater then or equal to the Btuh obtained for sensible heat is that the _____ contained in the air has heat content.
MOISTURE
88
An air system which contains the heating and cooling coils in a parallel flow is considered to be a ____-____ system.
DUAL-PATH
89
____ is the _____ or _____ axis distance an airstream travels after leaving the air outlet.
THROW, HORIZONTAL OR VERTICAL
90
Friction head pressure represents the ______ that the pumped liquid must ______.
RESISTANCE, OVERCOME
91
The steam tables are based on ___ pound of water converting to one pound of ____.
ONE, STEAM
