UNIT 73 REVIEW QUESTIONS ANSWER KEY GO BACK TO INDEX
73-1) What friction rate should be used to size a duct for a static pressure drop of 0.1”
WC if the duct has a total equivalent length of 150 feet?
73-2) What size metal duct should be used to deliver 170 CFM with a pressure drop of
0.15” if the total equivalent length is 130 feet?
73-3) What friction rate should be used to size a duct for a static pressure drop of 0.1”
WC if the duct has a total equivalent length of 50 feet?
73-4) What size metal duct should be used to deliver 290 CFM with a pressure drop of
0.12” if the total equivalent length is 80 feet?
73-5) What is the velocity of 500 CFM of air moving through a 10 inch duct?
73-6) Why should all ductwork designs start with an accurate heat loadstudy?
73-7) What is the total available static pressure for the ductwork for a system with the
following specifications:
73-8) Why should air velocity in branch ducts be limited to 600 feet per minute?
73-9) Why are duct friction charts designed for sheet metal duct ducts not accurate for
fiberglass ductboard or flexible ducts?
73-10) Why do fiberglass ductboard and flex duct have higher friction loss rates than
sheet metal?
73-11) What is the purpose of reducing the trunk duct size in a reducing extended plenum
duct system?
73-12) What is the maximum static pressure difference that most residential blowers are
designed for?
73-13) What is the recommended face velocity for a return air filter grille?
73-14) Explain what manufacturers mean by a register’s throw?
73-15) List the factors to consider when choosing a supply register.
• required CFM
73-16) What are the noise criteria curves?
73-17) Using Figure 71-25, select a floor register that will provide an 8 to 10 foot throw
for 150 CFM with a face velocity less than 700 feet per minute.