Manual Q

Question 1

A round commercial diffuser has a neck velocity of 700fpm. What is the average total pressure drop across the diffuser?

Answer 1

.075inwc

Pg. A 4-9 Manual Q

Question 2

What is the maximum negative pressure you are allowed to run in round steel duct in commercial applications?

Answer 2

3inwc

Pg. 2-1 Manual Q

Question 3

Which of the following is the smallest size 2 inch louver with 45 degree blades that can be used to bring in 600cfm of combustion air to feed 3 furnaces and 2 water heaters in a commercial building?
32in x 28in
28in x 28in
24in x 28in
20in x 28in

Answer 3

32 x 28

Below 7000cfm=300fpm 
300fpm x Area(sqft)= 600cfm
600/300=2sqft
300fpm x 2sqft= 600cfm
Must have 2sqft of free area.  

Pg. A 3-9(Louver Face Velocities)
Pg. A 4-10(Louver Free Area)
Manual Q

Question 4

What is the acceptable slope for a converging(reducing) transition in commercial duct systems?

Answer 4

1:4

Pg. 5-6 Manual Q

Question 5

What is the roughness index for fiberglass ductboard constructed with good workmanship?

Answer 5

.003

Pg. A 3-5 Manual Q

Question 6

A 24in round spiral duct is being used for main return duct in a high class restaurant, what is the approximate maximum cfm based on velocity restrictions in ACCA Manual Q?

Answer 6

4712cfm

Max Velocity = 1500fpm
CFM = Velocity(fpm) x Area(sqft)
Area of a Circle = ⫪r²
Radius = 1/2 x Diameter
Radius = 1/2 x 24in
R = 12in
A = 3.14 x 12in²
A = 3.14 x 1ft²
A = 3.14ft²
CFM = 1500fpm x 3.14ft²
CFM = 4712

Pg. A 3-9 Manual Q

Question 7

Which of the following dampers are not approved as a balancing damper?

• Opposed Blade
• Parallel Blade
• Splitter Damper
• Butterfly Damper

Answer 7

Splitter Damper

Pg. 9-4 Manual Q