Ducting PPT

Question 1

Air obeys which two gas laws?

Answer 1

Charles and Boyles

Question 2

Moving air prevents ____________

Answer 2

Stratification

Question 3

Air settling at different heights according to temperature is described as?

Answer 3

Stratification

Question 4

What components have an effect on stratification?

Answer 4

Thermostats and ducting outlets

Question 5

Factors for calculating air changes (6)

Answer 5

1. # occupants
2. use of space
3. dry-bulb temps
4. RH
5. fresh air admitted by infiltration
6. efficiency of unit

Question 6

Name four types of duct systems:

Answer 6

Radial
Extended Plenum
Reducing Trunk
Perimeter loop

Question 7

Name a few non-metal duct types

Answer 7

Fiberglass
Urethane
Plastic
Sheetrock
Textile

Question 8

Ducts made of fibreglass or asbestos should be ____________

Answer 8

plastic-coated

Question 9

Which types of ducts must be replaced when installing a new furnace?

Answer 9

Asbestos

Question 10

Asbestos is classified as a _________

Answer 10

carcinogen

Question 11

Removal of asbestos shall be done only by who?

Answer 11

abatement companies

Question 12

Duct size transitions should be tapered:
- Reductions: __” for every 4” in length.
- Enlargements: 1” for every 4 - __” in length

Answer 12

1”
4-7”

Question 13

Aspect ratio of ducting shall be :

Answer 13

1:1

Question 14

Diffusers spread air more uniformly than registers. True or False?

Answer 14

True

Question 15

Grilles are non-adjustable fixtures that cover return duct inlets. True or False?

Answer 15

True

Question 16

Registers do what?

Answer 16

Deliver air to a room

Question 17

Dampers control air flow; name 3 types

Answer 17

1. multiple-blade damper
2. butterfly damper
3. split-damper

Question 18

Most dampers have automatic controls that open or closed based on the __________

Answer 18

thermostat

Question 19

Power devices for dampers include 4 types; name them

Answer 19

1. electric motors
2. pneumatic motors
3. hydraulic motors
4. solenoids

Question 20

In a pneumatic system, air lines are controlled by the?

Answer 20

thermostat

Question 21

Pneumatic systems are most commonly used in what applications?

Answer 21

large commercial and industrial systems

Question 22

What are the two types of fire dampers?

Answer 22

static and dynamic

Question 23

What are the three rating classifications for fire dampers?

Answer 23

Class A
Class B
Class C

Question 24

Before installing ducts, check local ____ damper regulations

Answer 24

fire

Question 25

Turbulence can be caused by abrupt changes in _______ of airflow

Answer 25

direction

Question 26

_____-______ elbows minimize turbulence

Answer 26

long-radius

Question 27

You can minimize turbulence in short-radius elbows by using elbows with built-in ________ _____

Answer 27

directional vanes

Question 28

Never install duct at the end of ?

Answer 28

The plenum

Question 29

Some things to consider when designing ducting (4)

Answer 29

1. air handler central 2. short runs 3. minimize fittings 4. avoid obstacles

Question 30

Before sizing ducts, the technician must know what?

Answer 30

Heating and cooling loads

Question 31

Which mode requires more CFM and why?

Answer 31

Cooling due to moist coil and dense air must be overcame heat rises

Question 32

Airflow through a blower depends on what two factors?

Answer 32

External static pressure and blower speed

Question 33

What is ASP?

Answer 33

Available static pressure - amount of friction or resistance used to design longest duct run

Question 34

What is DPL?

Answer 34

Device pressure losses - pressure losses in system caused by devices other than ducts

Question 35

Friction losses are expressed in what units?

Answer 35

inches of water column

Question 36

Where do friction losses occur?

Answer 36

pressure drops inside the duct resulting from air contacting the surfaces

Question 37

To determine duct size, what are two tools you may use?

Answer 37

1. airflow friction chart 2. duct calculator

Question 38

Name some variables to consider when using an airflow friction chart?

Answer 38

duct diameters airflow rates pressure drops/friction losses air velocities

Question 39

What is the total pressure drop allowed?

Answer 39

0.5" w.c between supply and return air duct

Question 40

Device that blocks infiltration of outside air through an opening?

Answer 40

Air curtain?

Question 41

Ducting sections are connected with what type of cleats/fasteners?

Answer 41

S fasteners and D cleats

Question 42

Flexible duct connections reduce?

Answer 42

vibration/noise

Question 43

Where are duct connections assembled?

Answer 43

in the field

Question 44

Round ducting sections are connected with?

Answer 44

self tapping sheet metal screws

Question 45

Round duct requires more or less clearance than square/rectangular duct?

Answer 45

More

Question 46

Insulation and acoustic lining can be applied to the inside or outside of the duct. True or False?

Answer 46

True

Question 47

How is interior insulation secured to the duct?

Answer 47

tabs and washers, glue, or both

Question 48

Interior duct insulation is usually coated with what?

Answer 48

fibreglass

Question 49

One thing to be aware of when using interior acoustic lining for a duct is what?

Answer 49

reduces cross sectional area of the duct

Question 50

Ductboard can be fabricated easily using special?

Answer 50

knives

Question 51

How are sections of ductboard secured?

Answer 51

taping and stapling

Question 52

Flexible ducting should be stretched to prevent duct collapsing. True or False

Answer 52

True

Question 53

Flexible ducting has low initial costs and does not transmit noise well. True or False

Answer 53

True