Ductwork & Airflow
What two fasteners are typically used with sheet metal duct?
slips and drive
What is the dry-bulb temperature a measure of?
Sensible heat
Which system is more efficient—package or split?
Package
What thermostat-controlled device powers the control system?
Transformer
What gas may be present if a house is built on uranium-rich soil?
Radon
What is the term for resistance to airflow in each foot of duct?
Friction loss
What is it called when DB and WB temps are the same?
100% relative humidity
What line in the condensate system needs a trap to prevent air being pulled in?
Drain Line
What instrument measures air velocity?
Velometer
What material combo is most common in coils?
Copper tube–aluminum fin
What device creates the pressure difference to push air through a duct system?
Blower
What does the wet-bulb depression tell you?
Difference between DB and WB temps
Which part of a package unit must be field-installed?
None; all pre-installed
What instrument is used to read pressure in duct systems?
Manometer
Why is stainless steel used for screws in salty air?
Resists corrosion
What pressure unit is used for duct airflow measurement?
Inches of water column
What is the dew-point temperature?
Temp at which moisture condenses
What component cools the motor in a reciprocating compressor?
Suction gas and air
What happens if you switch to a high-density filter without adjusting airflow?
Airflow is reduced
What does a homeowner in the desert need to lower to reduce AC load?
Solar load
What’s one reason a reducing plenum system is used?
To maintain constant pressure in the trunk duct
What is the ideal comfort condition for temperature and humidity?
75°F and 50% RH
Why would an evaporator coil need multiple circuits?
To prevent refrigerant pressure drop
What does a hiss from the line set plugs during removal indicate?
No leak; sealed pressure)
What are three steps to control indoor air contamination?
Clean air, ventilate, eliminate source