# Tech Essay

428 Words2 Pages
Homework Unit 57 Section 7 1. What friction rate should be used to size a duct for a static pressure drop of 0.1 in wc if the duct has a total equivalent length of 150 ft? (57.10) 2. What size metal duct should be used to deliver 170 CFM with a pressure drop of 0.15 in wc if the total equivalent length of 130 ft? (57.10) 7 in. 3. What friction rate should be used to size a duct for a static pressure drop of 0.1 in wc if the duct has total equivalent length of 50 ft? (57.10) 0.2 4. What size metal duct should be used to deliver 270 CFM with a pressure drop of 0.15 in wc if the total equivalent length is 80 ft? (57.10) 8 in 5. What is the velocity of 500 CFM of air moving through a 10 in duct? (57.10) 900 fpm. 6. Why should all duct work designs start with an accurate heat load study? (57.1) Proper duct system designs are critical to the energy efficiency of a building. 7. Explain the function of the following duct components: (57.2) Ell are elbows used to make turns in ductwork, Wye is used to split one large duct into two smaller ducts, Transition is used to change rectangular ducts from one size to another, Boot is used at the end of a round duct to allow connection of a rectangular register or grill. 8. What is the total available static pressure for ductwork for a system with the following specifications? (57.13) 9. Why should air velocity in branch ducts be limited to 600 fpm? (57.13) If air moves faster than 600 fpm it begins to make noise. 10. Why are duct friction charts designs for sheet metal not accurate for fiberglass duct board or flexible ducts? (57.11) Most duct friction charts are designed for sheet metal not fiberglass or flex duct. 11. What is the difference between duct liner and duct wrap? (57.8) Duct liner is applied to the inside of the duct and duct wrap is fiberglass with an outer vapor barrier. 12. What is