Residential HVAC Installation
What two fasteners are used with sheet metal square and rectangular duct?
"S" fasteners (slips) and drive clips.
If a material has an R-value of 30, then the corresponding U-value will be ____.
.033
There are _ microns in 1 mm Hg.
1,000
Which of the following represents the lowest vacuum?
1,000 microns
The atmosphere exerts a pressure of ____ at standard atmospheric conditions.
14.696 psi
A(n) ____ºF temperature difference from the inside to the outside of the duct is considered the maximum difference allowable before insulation is necessary.
15
The typical gauge wire that is used in low voltage control circuits is _ gauge.
18
The simple way to check for airflow is to see if you can feel the airflow at a distance of about ____ from each register.
2 to 3 ft
Flexible round duct comes in sizes up to about _ in. in diameter.
24
If the equivalent length of a transition piece of ductwork is 10 feet and the main duct in series with it is 20 feet, what is the length used to estimate the total frictional loss?
30 feet
A deep vacuum involves reducing the pressure in a refrigeration system to a micron gauge reading of _ or below.
500 or below.
At what pressure range does the technician valve off the vacuum pump when evacuating to a deep vacuum?
500-300 microns
For calculating the heat gain from appliances, the guideline typically applied to a house with only a refrigerator and a vented cooking surface is ____ Btu/h.
600
The net wall area can be expressed mathematically as: ____.
Net Wall Area = Gross Wall Area - Door Area - Window Area - Area of other components
_ walls are walls that separate a conditioned interior space from an unconditioned interior space.
Partition
The heat transfer rate through a window is found through: ____.
Q = U-value × TD × Area
The sensible heat portion of the duct load can be calculated as: ____.
QSENSIBLE DUCT LOAD = Envelope Load × Duct Load Factor × Duct Insulation Correction
One of the most commonly used characteristics of building construction materials is the ____-value.
R
The ____-value is typically used to rate the thermal resistance of insulation materials.
R
What fastener is commonly used with round flexible duct?
Self-tapping screws.
Which of the values given below corresponds to a wall with the highest resistance to the pass of heat?
U-value = 0.80.
An auxiliary drain pan under the unit is recommended when the evaporator is installed ____.
above the conditioned space
A micron gauge is used to measure ____.
absolute pressures below 1 mm Hg
When moisture is present in a refrigeration system, it will react with the refrigerant and the oil to form ____.
acid
A trap in the condensate line prevents ____.
air from being drawn up into unit from the end of the drain
A split central air-conditioning system is installed with the control transformer located in the attic-hung air handler and the condensing unit located outside. The low voltage wire from the thermostat is run to the _.
air handler
A compound gauge ____.
all of the above
One drawback of using custom made, pre-fabricated duct sections is that ____.
all the above
Noncondensable gases ____.
are undesirable in a refrigeration system
The most basic heat gain and heat loss calculations are based solely on the ____ of the space being conditioned.
area
The term ____ is used to describe walls or portions of walls that are below ground level.
below grade
A boot in a duct system is a fitting used ____.
between the branch duct and the supply register
The ____ provides the pressure difference needed to force the air into the duct system, through the heat-transfer surfaces in the conditioning equipment, through the grilles and registers, and into the room.
blower
Probably the easiest way to determine what size lumber was used to frame a house is to inspect the _.
blueprint
To insure accurate testing, the best material to use for connecting lines to the vacuum pump and gauge set is ____.
copper tube
After refrigerant lines have been installed, they should be evacuated to a(n) ____ vacuum.
deep
The _ is simply the sum of the individual heat losses of the structure.
envelope load
Adjusting the tension on the belt will alter the rate at which air is moving through the system but does not affect the amperage draw of the motor.
false
After repairing a system that has had an electrical motor failure (compressor burnout), it is good field practice to re-use the recovered refrigerant in that system.
false
Canvas collars are generally made of canvas rather than other materials such as rubber.
false
Clearance tolerances are such that the ordinary clean refrigerant oil can be used satisfactorily in a vacuum pump.
false
Construction materials have a minor effect on the rate of heat transfer through the structural envelope.
false
Friction due to air rubbing the walls of the ductwork can be eliminated.
false
Once the power has been connected to the condensing unit of a package air conditioner, it is a good idea to start the compressor immediately to make certain it runs.
false
Power to the control transformer is controlled by the conditioned area thermostat.
false
The occupants of a house do not add to the heat gain of the structure.
false
The total heat loss for the basement walls is the product of the heat losses for the below-grade and above-grade walls.
false
Very little heat is lost through the roof.
false
When hanging a horizontal air handler, it should be pitched toward the drain port for proper condensate removal.
false
When it comes to sizing air conditioning and heating equipment bigger is definitely better.
false
When the length of quick-connect precharged line sets is altered, the charge will not normally have to be altered.
false
While under a deep vacuum, any liquid water under the oil in the motor-compressor assembly can be removed by operating the compressor motor for several seconds without any adverse effect on the system.
false
____ used at the end of a metal duct run will help reduce any noise that may be traveling through the duct.
flexible duct
Each foot of duct offers a known resistance to airflow which is called _.
friction loss
Galvanized sheet metal comes in several different thicknesses, called the _ of the metal.
gauge
The term that is used to describe the area of a wall before any doors or windows are cut into it is _.
gross wall area
A(n) _ pressure could also mean refrigerant vapor is still seeping from the refrigeration system.
high-rising
The pressure in a duct system is measured in ____.
in. WC
The electronic vacuum gage is attached to the system so it can measure the pressure _ the system.
inside
Before a system is evacuated, all piping should be filled with nitrogen and a small amount of refrigerant, in order to be _ checked.
leak
Micron gauge displays can be electronic analog, digital, or _.
light emitting
To pull a vacuum means to ____.
lower the pressure in a refrigeration system below atmospheric
The reason for using a reducing plenum system is to ____.
maintain a constant pressure throughout the length of the trunk duct
A(n) ____ can be connected to measure the velocity pressure of the air moving in a duct.
manometer
Baseboard hot water heat is an example of _ heat.
natural draft
Sludge is produced when moisture, acid, and _ are present in the system.
oil
When using a "standing pressure test" for leak-checking, _ should never be used since an explosive mixture can be created.
oxygen
One reason for using an extended plenum system is to ____.
prolong the main plenum closer to the farthest supply register
The U-value and the _ are inverses of each other.
r-value
Only two substances should be in the refrigeration system for proper operation. They are _ and oil.
refrigerant
A round to rectangular fitting is called a(n) _.
square to round transition Correct.
The best method of leak checking is when the refrigeration system is ____.
standing with dry nitrogen pressure of 150 psig in the system
What two fasteners are used with fiberglass ductboard?
staples & tape
A good way to fasten acoustical lining to the inside of sheet metal duct is to use ____.
tabs and adhesives
As the ____ increases, the rate of heat transfer from one side of the structure to the other will increase.
temperature differential
A fitting used to change the size of a square or rectangular duct is called a(n) _.
transition
A device used to put trunk duct or extended plenum sections together is called a drive clip.
true
Air entering a refrigerant system can eventually lead to compressor failure.
true
Application of acoustical lining to the interior of a duct is accomplished by using tabs, glue, or both.
true
Duct systems can be plenum, extended plenum, reducing plenum, or perimeter loop.
true
One purpose of a flexible duct connector in a duct system is to reduce the transmission of noise and vibration.
true
Oversized air conditioning equipment will cool the space faster.
true
Oversized duct systems cost more to fabricate and install and will also result in the slowing of the air as it flows through the duct.
true
The duct pressure equals the velocity pressure plus static pressure.
true
The forced-air system is different from a natural-draft system, where the air passes naturally over the conditioning equipment.
true
The heat gain on a structure can be summarized as the sum of the conduction loads, the internal loads, the solar loads and the infiltration loads.
true
The main drawback of the extended plenum system is that the velocity of the air is lower as the air reaches the last takeoffs on the extended plenum.
true
The maximum recommended pressure for leak testing is 150 psig on the low-pressure side of the system.
true
The oil in a vacuum pump should be changed after each time it is used.
true
The sun shining on the panels and coils of the condensing section will lower the efficiency of the unit.
true
The temperature on both sides of an exterior wall or panel is needed to help determine how much heat is entering or leaving the structure.
true
The total heat loss for a structure is simply the sum of the heat losses experienced by all of the construction elements that make up a particular structure.
true
The two important factors that affect the U-value for the below-grade portion of the wall are the materials used to construct the wall and how far below grade the floor is.
true
There are different methods to calculate the heat gain on a structure based on the type of house and the number of wall exposures it has.
true
When installing a split air-conditioning system with a remote condensing unit, the line set may be altered if the standard length was incorrect for installation.
true
When removing the rubber plugs from a line set, the hiss indicates that the tubing is not leaking.
true
Moisture in a liquid state must be ____ before it can be removed with a vacuum pump.
vaporized
An instrument that is commonly used on air distribution systems is the anemometer, or ____.
velometer
Airflow pressure in ductwork is measured in inches of ____.
water column
A multiple evacuation means that ____.
you pull a vacuum on a refrigeration system more than once, allowing refrigerant or nitrogen into the system between each procedure
