Residential Hvac Components (110104f) Flashcards
What’s the max ratio of duct?
4 to 1
List all the parts required for a branch run?
Duct takeoffs, piping and boots (pipe to diffuser transitions)
What are the three most common boots for hvac?
End boot, u boot, right angle boot
Why are stack ducts used?
To transition from round to rectangular and back again
Never in real world you would use oval pipe and 2 round to oval 90’s
What encases the under slab heating duct?
Round duct encased in concrete
Which way does the under slab heating duct slope to the furnace
Back to the furnace
What are two types of vent connector that can be used?
Single wall
Double wall
What does pto stand for?
Plenum take off
What is used to hang duct from floor joists?
Duct hangers
Residential pipe elbows are equivalent to how many feet of pipe?
10 feet, adding 1 elbow equals 10 feet of pipe.
Roof jacks used on dryer vents are not equipped with?
Bird screens
The combustion air termination is used to?
Keep cold air from dropping into the furnace room
A 14 inch by 8 inch return air grill covers?
A 14 inch by 8 inch hole
When a return air branch run is finished on the bottom with drywall ceiling, the bottom part of the branch run is finished with?
Drywall
What is a reducer or transition
A reducer or transition changes the size of the duct smoothly.
What are different types of takeoffs?
Top , side , two way, saddle, universal
What is joist liner?
A product used to finish closing off the joist space for return air.
Where does the drop duct connect?
The furnace through the filter rack
What is the heart of the hvac system?
Air recirculation fan
Furnaces require air to fuel the fire inside of them this is called?
Combustion air
Name 4 things that can cause dynamic loss in an airstream?
Material duct is constructed from
Shape of duct
Changes in direction
Changes in cross sectional area
Dynamic losses on flexible duct are approximately how many times great per foot as in smooth duct?
10
You should always install 2 elbows together (back to back) true or false?
False
What is exfiltration?
The uncontrolled leakage of air from a building
What is return air?
Air from the occupied space returned to furnace
What is joist lining made from?
Metal, thermopan, plastic or drywall
Where does a filter rack install?
Between furnace and drop duct
Return air duct is mounted tight to what?
Floor joists
Underslab heating uses what kind of duct?
Round duct that is encased in concrete
What is the standard for (BH) venting?
ULC S636
The combustion process requires what from the air for combustion?
Oxygen
What is an intake hood for?
To bring combustion air into the building
What does the return air system consist of?
All the parts from the return air grilles in the room right back to the furnace
If heat is supplied by burning a fuel in the heat exchanger it is called?
A furnace
If hot water supplies the heat it is called?
A fan coil unit
Where should supply outlets (boots) be placed in a room?
At the point of greatest heat loss or gain.
Under windows or besides doors
What is ratio for pto front to back?
Back towards furnace is 1.5 times the other side towards the duct
What is recommended length of the offset fitting?
2 times the amount of the offest
Pipe supports are required at?
Every joint or elbow
What is a frost wall?
A 2x4 wall insulated wall built on the inside of the concrete basement wall
B vent piping for venting is rated to withstand how high of a temperature?
470 Fahrenheit
243 Celsius
Exterior terminations are called what?
Hoods and roof jacks
Exhaust hoods require what?
A flap
Fresh air hoods do not
What is the difference between B and BW vent
BW vent is oval
What venting can be used for oil burning appliances?
A vent and L vent
What is the most common duct installed today?
Extended plenum or reducing extending plenum
What shape of duct is best? And what other kinds are used also?
Round duct is best
Square duct is next best after round
Rectangular duct is next best after square
What is the main purpose of a plenum?
To calm the turbulent air that is coming out of the furnace before being distributed
What is needed to order a plenum?
Length
Height
Width
What is the standard practice dictated for a pto?
The inlet of the pto is 1.5x the cross sectional area of the duct it is being attached to
How is a pto ordered?
Duct width x duct height x rise also with a 2 to 4 inch rise or flat top in some cases
What are duct hangers made 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 that has a 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?
If an elbow has a change in size from one end to the other it is called a change elbow
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? (8x30)
The first number is the size of the cheek therefore 8” cheek
What is L vent constructed from?
Galvanized outer, airgap space, stainless steel inner liner
Where are end caps used?
At the end of every duct run
What is BH venting?
BH vent is a special venting stainless or plastic used for condensing furnaces
Dynamic losses occur in both Rectangular and round duct?
True
What is modern fresh air ducting?
Flexible insulated ducting
How are bathfans most commonly vented? And how else are they vented?
-Insulated flex pipe
-Solid metal pipe when close to exterior wall must be insulated
What is a kitchen fan called?
Range vent
What’s the difference between class A and super class A venting?
Super A has 2 inch of insulation between the inner liner and outer casing. This allows the chimney to withstand 1200 f continuously and up to 2100 f for 10 minutes.
Should B vent material be cut or modified?
No
If basement is unfinished where must joist liner be installed?
On the bottom of the joist return air is in with block ends
Why do return air frames have a 1/2 flange?
To help dry wall installers to cut a neat hole in drywall of the correct size
What kind of pipe is used in residential installs?
Snap lock most common sizes are 4”, 5” and 6” other sizes used are 8” and 10” sold in 5’ lengths
What is B vent made of?
Inner aluminum liner
Airspace
Outer galvaluminum (470 degrees F) 243 degrees C
FOT meaning?
Flat on top
What is a branch run?
Terminations from the main duct to deliver air to the different terminations
When venting an appliance that burns natural gas or propane what venting is used?
B vent
What is the best style of duct for less dynamic loss?
Round duct
Most commonly used duct in residential installs?
Rectangular to save headroom in a basement sold in 5’ lengths
What pipe is used on duct runs for underslab heating?
Spiral pipe
When is make up air possibly required?
When extra exhaust fans are installed
