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Residential Air Conditioning

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What kind of copper tubing is used for refrigeration or air-conditioning applications?
ACR (air-conditioning refrigeration) tubing
What kind of copper tubing is used for plumbing and heating applications?
nominal-sized tubing
How is ACR tubing sized?
outside diameter (OD)
How is nominal-sized tubing sized?
inside diameter (ID)
Why are some ACR tubing lines insulated?
to keep refrigerant from absorbing heat and to prevent condensation from forming on the line
Where is insulation used on copper tubing used for air-conditioning?
the suction line or the low-pressure side
In what length rolls is soft copper tubing normally available?
25-ft or 50-ft
What standard weight copper tubing is most often used in the heating and air-conditioning industry?
L-type
Where do you apply flux when soldering?
outside of the male fitting
What percentage silver do you use to braze two dissimilar metals such as steel and copper?
45-55%
How much does a drain line need to drop per foot of length?
1/4"
At what temperature will soft solder melt?
below 800 degrees F
At what temperature will brazing melt?
over 800 degrees F
What are the three ways a motor can fail electrically?
shorted winding, open winding, and grounded winding
How long should you leave a system off once you kill power before restarting it?
2 minutes
In what state is the refrigerant in the compressor?
vapor
What is it called when liquid refrigerant gets into the compressor?
slugging
How much superheat do you need to prevent liquid refrigerant from entering the compressor?
any amount
What is considered normal operating conditions?
75 degrees F dry bulb indoor, 95 degrees F drybulb outdoor, and 50% relative humidity
What is a package unit?
An air-conditioning system that has all four components (compressor, condenser, metering device, and evaporator) in one housing.
What are the two types of package units?
side-by-side and over-and-under
A reciprocating compressor has what sort of moving parts?
pistons
If the rpm's are 3450, how many poles does the motor have?
2
If the rpm's are 1750, how many poles does the motor have?
4
If the rpm's are 1050, how many poles does the motor have?
6
If the rpm's are 750, how many poles does the motor have?
8
How is the high pressure switch wired with the low pressure switch?
in parallel
How are the high pressure switch and the low pressure switch wired with the compressor contactor?
in series
What are the components of a hard-start kit?
potential relay and start capacitor
What is the typical pressure differance across a TXV?
100 psig
How many cfm per ton?
400
How many BTU's per ton?
12,000
When do you install a trap on a drain line?
when it is a pull-through evaporator
How is insulation around a duct rated?
with an R rating
When do you install an auxillary drain pan?
when it is above a conditioned space
What sort of pressure will a pull-through evaporator have?
negative
What sort of pressure will a push-through evaporator have?
positive
Where do you install a trap on a drain line?
before the vent
Do you need a trap on a pull-through evaporator?
yes
Do you need a trap on a push-through evaporator?
no
Do you need a vent on a push-through evaporator?
yes
Do you need a vent on a pull-through evaporator?
yes
What is lined duct?
duct with insulation on the inside
How many amps can 14 g wire handle?
15 A
How many amps can 12 g wire handle?
20 A
How many amps can 10 g wire handle?
30 A
How many amps can 8 g wire handle?
40 A
Superheat should never be below how many degrees
5 degrees
How does ACR copper pipe come?
dehydrated with caps on each end
The A/C size is calculated by what?
heat load
The furnace size is calculated by what?
heat loss
Where do you check the amps on a motor?
on the common terminal
How do you calculate cfm?
average feet per minute X area in square feet (H" x W"/144)
How do you calculate the area of a circle?
pi x radius squared
What do you use to connect square and rectangular ductboard together?
S-clips and drives (cleats)
What distributes supply air to a room in a structure?
a diffuser
What do you use to check for leaks?
nitrogen with a small amount of refrigerant
What do you do after you braze a system?
pull a vacuum
What percentage silver do you need to use for an R-410 system?
15% silphos
Which is more efficient, a TXV or a fixed-orifice metering device?
TXV
What is the design boiling point for most evaporator coils in residential air conditioning?
40 degrees F
What are the three crafts normally associated with an air-conditioned installation?
duct, electrical, and mechanical
How are round ducts connected to one another?
with a minimum of three evenly spaced self-tapping screws
Most duct insulation is made of what?
fiberglass
How is flexible duct supported?
a band 4 inches or more in width
Does a package unit come from the factory pre-charged?
yes
On what terminal do you check amperage?
common
What is used to measure static air pressure in ducts.
inclined manometer
Will a dirty condenser cause a rise or fall in pressure?
rise
If pressure rises, what happens to the superheat?
it rises
The load on the evaporater will effect which pressure?
suction
How do you calculate ballpark superheat?
subtract ambient temperature from 100
How will too much refrigerant effect subcooling?
it will be high
How will too much refrigerant effect superheat?
it will be low
What kind of refrigeratnts must be added in liquid form?
blended refrigerants
What gauge is thermostat wire?
18 gauge
Which type of wire can handle a higher ampacity?
stranded
What is the normal evaporator temperature?
45 degrees F
What is the range for normal superheat and subcooling?
8-12 degrees F
At what temperature does refrigerant condense in a standard-efficiency unit?
30-35 degrees above ambient
10 SEER is classified as what kind of efficiency?
standard
13 SEER is classified as what kind of efficiency?
high
At what temperature does refrigerant condense in a high-efficiency unit?
20 degrees above ambient
How are the condenser coils different on a high-efficiency unit?
they are larger
What kind of metering device do high-efficiency units usually use?
TXV
6" round duct has a ballpark cfm of what?
100
7" round duct has a ballpark cfm of what?
150
8" round duct has a ballpark cfm of what?
200
9" round duct has a ballpark cfm of what?
300
10" round duct has a ballpark cfm of what?
400
How do you calculate LRA?
RLA/FLA x 5
The fan switch closes at what temperature?
140 degrees F
The fan switch opens at what temperature?
105 degrees F
What are the four materials used to make duct?
sheet metal, galvanized sheet metal, fiberglass, and flexduct
How are round ducts supported?
with 4" saddles
What are normal conditions, as defined by the ARI.
95 degrees F outside, 80 degrees F inside, and 50% relative humidity
What is the typical temperature difference between a standard-efficiency condenser and the ambient temperature?
30 degrees F
What is the typical temperature difference between a high-efficiency condenser and the ambient temperature?
20 degrees F
The refrigerant within the evaporator will typically boil at what temperature when it is 75 degrees inside with a relative humidity of 50%?
40 degrees F
If the suction pressure rises, what happens to the head pressure?
it also rises
What is the difference between SEER and EER?
SEER includes the energy used in the start-up and shut-down cycles
What are the three major power-consuming devices on an air-conditioning system?
indoor fan motor, outdoor fan motor, and the compressor
What is the name of the fitting where the branch line leaves the duct?
the takeoff fitting
Multiple-zone systems often use what to alleviate the problem of excess air when only some zones are calling for conditioning?
a bypass duct or a dump zone
What are the two ways that fresh air enters a structure?
infiltration and ventilation
What are the two types of blower drives?
belt drive and direct drive
Pressure in ductwork is measured in what?
inches of water column (in. WC)
What are the three pressures created by moving air in ductwork?
static pressure, velocity pressure, and total pressure
What are the two types of return air systems in residential installations?
individual return air systems and central return air systems
How are high-efficiency condenser coils different from standard-efficiency condenser coils?
they are physically larger
How do you calculate EER?
Btu/hr (output) / wattage (input)
What component changes refrigerant from a low pressure gas to a high pressure gas?
compressor
When must a copper joint never be soldered or brazed?
when the system is under pressure
What are the two functions of the air-conditioning system?
to remove humidity and lower dry bulb temperature
What can cause a decrease in suction pressure on an air-conditioning system?
a dirty evaporator
How will an overcharge affect an air-conditioning system with a fixed-orifice type metering device?
it will have a decrease in superheat
Why is it necessary to have multiple refrigerant circuits in some evaporator coils?
to lower the amount of pressure drop through the coil
The evaporator is designed to remove what two types of heat?
latent and sensible
The compressor is cooled by liquid refrigerant. (True of False)
false
Square sheet metal duct is normally fabricated in a sheet metal shop and assembled in the field. (True or False)
true
The crankcase heater on an air-conditioning compressor is used to what?
boil the liquid refrigerant out ot the oil within the crankcase
Sections of duct board can be fastened together with what?
staples and tape
How do you achieve high-efficiency?
by increasing the surface of the condenser coil
What type of air conditioning system must be charged using the superheat method?
a piston type metering device
What tool is used to expand the diameter of soft copper tubing
a swaging tool
What are the two basic duct connection configurations for package units supply and return air ducts?
over/under and side by side
Can refrigerant line sets be altered in length?
yes