Deck 37: Air Distribution and Balance

Question 1

The simple way to check for airflow is to see if you can feel the airflow at a distance of about ____ from each register.

A) 2 to 3 ft
B) 3 to 5 ft
C) 5 to 8 ft
D) 8 to 10 ft

Answer 1

A

Question 2

Adjusting the tension on the belt will alter the rate at which air is moving through the system but does not affect the amperage draw of the motor.

Answer 2

False

Question 3

One reason for using an extended plenum system is to ____.

A) save materials
B) reduce the velocity of the air as the air reaches the last takeoffs on the extended plenum
C) prolong the main plenum closer to the farthest supply register
D) keep the noise level low

Answer 3

C

Question 4

Oversized duct systems cost more to fabricate and install and will also result in the slowing of the air as it flows through the duct.

Question 5

The atmosphere exerts a pressure of ____ at standard atmospheric conditions.

A) 12.696 psi
B) 14.696 psi
C) 16.696 psi
D) 18.696 psi

Question 6

The forced-air system is different from a natural-draft system, where the air passes naturally over the conditioning equipment.

Question 7

Duct systems can be plenum, extended plenum, reducing plenum, or perimeter loop.

Question 8

The main drawback of the extended plenum system is that the velocity of the air is lower as the air reaches the last takeoffs on the extended plenum.

Question 9

Friction due to air rubbing the walls of the ductwork can be eliminated.

Question 10

The reason for using a reducing plenum system is to ____.

A) reduce maintenance costs
B) reduce the operating cost of the system
C) provide easier means of fastening the takeoff fittings
D) maintain a constant pressure throughout the length of the trunk duct

Question 11

The duct pressure equals the velocity pressure plus static pressure.

Question 12

The ____ provides the pressure difference needed to force the air into the duct system, through the heat-transfer surfaces in the conditioning equipment, through the grilles and registers, and into the room.

A) blower
B) forcer
C) compressor
D) condenser

Question 13

A(n) ____ can be connected to measure the velocity pressure of the air moving in a duct.

A) ammeter
B) manometer
C) pyrometer
D) speedometer

Question 14

Canvas collars are generally made of canvas rather than other materials such as rubber.

Question 15

Airflow pressure in ductwork is measured in inches of ____.

A) mercury pressure
B) water column
C) air pressure
D) mercury column

Question 16

The pressure in a duct system is measured in ____.

A) psig
B) psia
C) in. Hg
D) in. WC

Question 17

An instrument that is commonly used on air distribution systems is the anemometer, or ____.

A) velometer
B) manometer
C) pyrometer
D) ammeter

Question 18

If the equivalent length of a transition piece of ductwork is 10 feet and the main duct in series with it is 20 feet, what is the length used to estimate the total frictional loss?

A) 10 feet
B) 20 feet
C) 30 feet
D) 60 feet

Question 19

A(n) ____ºF temperature difference from the inside to the outside of the duct is considered the maximum difference allowable before insulation is necessary.

A) 10
B) 15
C) 18
D) 20

Question 20

A device used to put trunk duct or extended plenum sections together is called a drive clip.

Question 21

How is the centrifugal blower turned?

Question 22

Why is the airflow from a register not the same across the entire surface?

Question 23

If the velocity of air through an 8" x 20" duct is 700 fpm, how many cfm of air is being carried by the duct?

Question 24

Each foot of duct offers a known resistance to airflow which is called ____________________.

Question 25

Baseboard hot water heat is an example of ____________________ heat.

Question 26

Flexible round duct comes in sizes up to about ____________________ in. in diameter.

Question 27

What are the components that make up the forced-air system?

Question 28

When is insulation required on air ducts?

Question 29

What is an air conditioning system's capacity in tons, if the supply air is moving through the 12" x 24" main supply duct at a velocity of 400 ft/min?

Question 30

A duct system is pressurized by what three pressures?

Question 31

Galvanized sheet metal comes in several different thicknesses, called the ____________________ of the metal.

Question 32

Describe the plenum system and explain why it is economical from a first-cost standpoint.

Question 33

Describe a pitot tube.

Question 34

Branch ducts should always use what component to balance the air to the individual areas?

Question 35

Explain the purpose of the supply duct.