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What kind of copper tubing is used for refrigeration or air-conditioning applications?
ACR (air-conditioning refrigeration) tubing
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
What standard weight copper tubing is most often used in the heating and air-conditioning industry?
What are the three ways a motor can fail electrically?
shorted winding, open winding, and grounded winding
How much superheat do you need to prevent liquid refrigerant from entering the compressor?
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.
How are the high pressure switch and the low pressure switch wired with the compressor contactor?
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
At what temperature does refrigerant condense in a standard-efficiency unit?
30-35 degrees above ambient
What are the four materials used to make duct?
sheet metal, galvanized sheet metal, fiberglass, and flexduct
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
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
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 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
What are the two functions of the air-conditioning system?
to remove humidity and lower dry bulb temperature
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
Square sheet metal duct is normally fabricated in a sheet metal shop and assembled in the field. (True or False)
The crankcase heater on an air-conditioning compressor is used to what?
boil the liquid refrigerant out ot the oil within the crankcase
What type of air conditioning system must be charged using the superheat method?
a piston type metering device
What are the two basic duct connection configurations for package units supply and return air ducts?
over/under and side by side
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