Residential HVAC Components (110104f)

Question 1

When should you use a longer duct run?

Answer 1

you should avoid it as longer runs lose air flow shorter runs are best

Question 2

What is the main purpose of the plenum?

Answer 2

to calm the turbulent air that is coming out of the furnace before being distributed

Question 3

what is needed to order a plenum?

Answer 3

Length x height x width

Question 4

What does PTO stand for?

Answer 4

Plenum Take Off

Question 5

What is the standard trade practice dictated for the PTO?

Answer 5

The inlet of the PTO is 1.5x the cross-sectional area of the duct it is being attached to

Question 6

How is a standard PTO ordered and how do they come?

Answer 6

Duct width x duct Hight x rise required they come as straight on top or with a 2-4 inch rise.

Question 7

what is common residential duct size?

Answer 7

8” that comes in 8’ or 5’ lengths

Question 8

what is the ratio between the with and depth of a duct?

Answer 8

4:1

Question 9

what are duct hangers constructed from in the field?

Answer 9

Drive cleats

Question 10

how can a change in airflow direction be achieved?

Answer 10

with the use of fittings like elbows offsets or branch fittings

Question 11

what is a short way elbow?

Answer 11

the elbow has the short dimension on the cheeks

Question 12

What is a long way elbow?

Answer 12

The elbow has the long dimension on the cheek

Question 13

What is a change elbow fitting?

Answer 13

the fitting has two different opening sizes the changes occur on the cheeks

Question 14

what are offsets and risers?

Answer 14

offsets move from side to side
risers move up and down

Question 15

how do you know what size to make the cheek? (8” x 30”)

Answer 15

the first number is the size of the cheek therefore 8” cheek

Question 16

what is the minimum that the offset has to be?

Answer 16

two times the offset

Question 17

why are transitions/ reducers used?

Answer 17

to change the size of the duct smoothly

Question 18

F1S meaning?

Answer 18

Flat one side

Question 19

C with a line through it is what?

Answer 19

on center or centerline

Question 20

FOT meaning?

Answer 20

Flat On Top

Question 21

were are end caps used?

Answer 21

at the end of every duct run

Question 22

What is a branch run?

Answer 22

they are terminations of the main trunk they supply air to the different terminations

Question 23

What are some common take offs?

Answer 23

Top take off
Side take off
Two way take off
Saddle take off
Universal take off

Question 24

what is the common type of pipe for residential?

Answer 24

snap lock pipe it is made in 5’ lengths

Question 25

what is a round-end cap called?

Answer 25

a plug

Question 26

When is a volume damper required?

Answer 26

at the end of each branch run and is placed in line close to the truck line or as a diffuser

Question 27

Were is pipe support required?

Answer 27

at every joint and elbow

Question 28

one pipe elbow is equivalent to how many feet of pipe?

Answer 28

10'

Question 29

what is a right-angle boot called?

Answer 29

RAB

Question 30

what are some common Boots?

Answer 30

End boot Universal boot Right angle boot Kickboot

Question 31

what are common boot sizes?

Answer 31

3" x 10" 4" x 10"

Question 32

what are stack ducts for?

Answer 32

transition from round to square and back helps for when ducts have to go up in walls

Question 33

What is the combustion air termination used for?

Answer 33

to isolate the combustion air and keep it from dumping cold air into the furnace room

Question 34

what is forced air that runs under the concrete called?

Answer 34

Under slab heating

Question 35

what do roof jacks on dryer vents not have that fresh air do?

Answer 35

Bird screen

Question 36

In what way must under slab branches flow?

Answer 36

back toward the furnace

Question 37

what is L-vent constructed from?

Answer 37

galvanized outer, airgap space, stainless steel inner liner

Question 38

what type of ducting is used for under slab and why?

Answer 38

round spiral for added strength

Question 39

what is the heart of the HVAC system?

Answer 39

Recirculation fan

Question 40

what type of take of is different for round pipe?

Answer 40

Saddle take offs are for pipe only

Question 41

what causes dynamic air loss?

Answer 41

How the duct is constructed shape of the duct changes in direction changes in cross-sectional areas use of fittings

Question 42

How many feet is equivalent in the use of flexible pipe?

Answer 42

10'

Question 43

does dynamic loss occur in square and round duct?

Answer 43

yes

Question 44

how are return air grills sized?

Answer 44

by the hole they cover

Question 45

what connects the return air trunk back to the furnace?

Answer 45

Drop duct

Question 46

when venting an appliance that burns natural gas or propane what venting is used?

Answer 46

they use b-vent

Question 47

what is b-vent made of?

Answer 47

inner aluminum liner, airspace, outer galvaluminum (470 degrees F) 243 degrees C

Question 48

what is BW-Vent

Answer 48

it has the same application as B-vent but is oval

Question 49

what is BH venting?

Answer 49

BH-vent is a special venting stainless or plastic used for condensing furnaces.

Question 50

what is the best style for less dynamic loss?

Answer 50

round spiral

Question 51

should two elbows be put back to back?

Answer 51

they should not

Question 52

where is fresh air connected in the HVAC system?

Answer 52

the return air at a minimum 10' away from the heat exchanger