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DUCT SIZING TEST

True/False
Indicate whether the sentence or statement is true or false.

1.

The amount of air flow (CFM) that is delivered by a blower depends on the resistance (pressure) that the blower has to work against?
True or False

2.

To meet the objective of good duct design, the duct system must be designed so that the air flow resistance , in terms of static pressure drop, matches the external static pressure that is developed by the blower when the blower delivers the desired CFM?
True or False

Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.

3.

A friction rate is equal to the pressure loss that occurs between two point in a duct system that are separated by a specific distance.Friction charts and duct slide rules use 100’ for the reference distance. What would you assume the pressure drop would be in a typical residential duct system.
 a. 0.5 “ W.C. c. 5” W.C. b. .1” W.C. d. .8” W.C

4.

The formula for finding FR when the system pressure drop is know is?
 a. FR=PD x100           100 c. PD=.5 x100          100 b. PD=FR x100           100 d. FR=.8x100         100

5.

How do you determine available static pressure when doing your design?
 a. Exam all device pressure losses and subtract from manufacturers external static pressure at your desired CFM c. Measure in field b. Blower static pressure measurement d. Calculated CFM

6.

Using your ductulator with a friction rate of 0.05 for galvanized duct @ 480 CFM what would the size of your round duct be for these conditions?
 a. 18” c. 9” b. 12” d. 8”

7.

Using your ductulator with a friction rate of 0.05 for galvanized duct @ 480 CFM what would the friction rate be for these conditions?
 a. 600 fpm c. 800 fpm b. 1200 fpm d. 400 fpm

8.

If you have a round duct diameter of 8” what would be the round duct area in square inches?
 a. 100 c. 52 b. 200 d. 5

9.

If you want to deliver in a rectangular duct which is 8 x ? an amount of air equal to 200 CFM at a 0.05 friction rate, what would the 8 x ? be?
 a. 10 c. 12 b. 14 d. 8

10.

To deliver 150 CFM of air to a space with a friction rate of 0.05 what size wire helical flexible duct would you need?
 a. 8 c. 7 b. 9 d. 6

11.

In a residence what would be the problem with a main duct run delivering 1,000 CFM @0.05 friction rate with a size being 50 x 8?
 a. Velocity to low and duct costly to fabricate, too large c. Velocity to high b. Nothing d. FPM to high

12.

If my duct system pressure drop is equal to 0.05 W.C and my duct is to delivery 200 CFM at a length of 200 feet, what would be my required design friction rate?
 a. .025 c. .45 b. .25 d. .65