Residential HVAC Components (110104f) Flashcards
When should you use a longer duct run?
you should avoid it as longer runs lose air flow shorter runs are best
What is the main purpose of the plenum?
to calm the turbulent air that is coming out of the furnace before being distributed
what is needed to order a plenum?
Length x height x width
What does PTO stand for?
Plenum Take Off
What is the standard trade practice dictated for the PTO?
The inlet of the PTO is 1.5x the cross-sectional area of the duct it is being attached to
How is a standard PTO ordered and how do they come?
Duct width x duct Hight x rise required they come as straight on top or with a 2-4 inch rise.
what is common residential duct size?
8” that comes in 8’ or 5’ lengths
what is the ratio between the with and depth of a duct?
4:1
what are duct hangers constructed from in the field?
Drive cleats
how can a change in airflow direction be achieved?
with the use of fittings like elbows offsets or branch fittings
what is a short way elbow?
the elbow has the short dimension on the cheeks
What is a long way elbow?
The elbow has the long dimension on the cheek
What is a change elbow fitting?
the fitting has two different opening sizes the changes occur on the cheeks
what are offsets and risers?
offsets move from side to side
risers move up and down
how do you know what size to make the cheek? (8” x 30”)
the first number is the size of the cheek therefore 8” cheek
what is the minimum that the offset has to be?
two times the offset
why are transitions/ reducers used?
to change the size of the duct smoothly
F1S meaning?
Flat one side
C with a line through it is what?
on center or centerline
FOT meaning?
Flat On Top
were are end caps used?
at the end of every duct run
What is a branch run?
they are terminations of the main trunk they supply air to the different terminations
What are some common take offs?
Top take off
Side take off
Two way take off
Saddle take off
Universal take off
what is the common type of pipe for residential?
snap lock pipe it is made in 5’ lengths
what is a round-end cap called?
a plug
When is a volume damper required?
at the end of each branch run and is placed in line close to the truck line or as a diffuser
Were is pipe support required?
at every joint and elbow
one pipe elbow is equivalent to how many feet of pipe?
10’
what is a right-angle boot called?
RAB
what are some common Boots?
End boot
Universal boot
Right angle boot
Kickboot
what are common boot sizes?
3” x 10”
4” x 10”
what are stack ducts for?
transition from round to square and back helps for when ducts have to go up in walls
What is the combustion air termination used for?
to isolate the combustion air and keep it from dumping cold air into the furnace room
what is forced air that runs under the concrete called?
Under slab heating
what do roof jacks on dryer vents not have that fresh air do?
Bird screen
In what way must under slab branches flow?
back toward the furnace
what is L-vent constructed from?
galvanized outer, airgap space, stainless steel inner liner
what type of ducting is used for under slab and why?
round spiral for added strength
what is the heart of the HVAC system?
Recirculation fan
what type of take of is different for round pipe?
Saddle take offs are for pipe only
what causes dynamic air loss?
How the duct is constructed
shape of the duct
changes in direction
changes in cross-sectional areas
use of fittings
How many feet is equivalent in the use of flexible pipe?
10’
does dynamic loss occur in square and round duct?
yes
how are return air grills sized?
by the hole they cover
what connects the return air trunk back to the furnace?
Drop duct
when venting an appliance that burns natural gas or propane what venting is used?
they use b-vent
what is b-vent made of?
inner aluminum liner, airspace, outer galvaluminum (470 degrees F) 243 degrees C
what is BW-Vent
it has the same application as B-vent but is oval
what is BH venting?
BH-vent is a special venting stainless or plastic used for condensing furnaces.
what is the best style for less dynamic loss?
round spiral
should two elbows be put back to back?
they should not
where is fresh air connected in the HVAC system?
the return air at a minimum 10’ away from the heat exchanger
